From ab33774676db3e419dd56b2001f0cbf2bc291d3d Mon Sep 17 00:00:00 2001
From: Masahiko Sawada <sawada.mshk@gmail.com>
Date: Wed, 14 Sep 2022 12:38:51 +0000
Subject: [PATCH v29 03/10] Add radixtree template

WIP: commit message based on template comments
---
 src/backend/utils/mmgr/dsa.c                  |   12 +
 src/include/lib/radixtree.h                   | 2516 +++++++++++++++++
 src/include/lib/radixtree_delete_impl.h       |  122 +
 src/include/lib/radixtree_insert_impl.h       |  328 +++
 src/include/lib/radixtree_iter_impl.h         |  153 +
 src/include/lib/radixtree_search_impl.h       |  138 +
 src/include/utils/dsa.h                       |    1 +
 src/test/modules/Makefile                     |    1 +
 src/test/modules/meson.build                  |    1 +
 src/test/modules/test_radixtree/.gitignore    |    4 +
 src/test/modules/test_radixtree/Makefile      |   23 +
 src/test/modules/test_radixtree/README        |    7 +
 .../expected/test_radixtree.out               |   36 +
 src/test/modules/test_radixtree/meson.build   |   35 +
 .../test_radixtree/sql/test_radixtree.sql     |    7 +
 .../test_radixtree/test_radixtree--1.0.sql    |    8 +
 .../modules/test_radixtree/test_radixtree.c   |  681 +++++
 .../test_radixtree/test_radixtree.control     |    4 +
 src/tools/pginclude/cpluspluscheck            |    6 +
 src/tools/pginclude/headerscheck              |    6 +
 20 files changed, 4089 insertions(+)
 create mode 100644 src/include/lib/radixtree.h
 create mode 100644 src/include/lib/radixtree_delete_impl.h
 create mode 100644 src/include/lib/radixtree_insert_impl.h
 create mode 100644 src/include/lib/radixtree_iter_impl.h
 create mode 100644 src/include/lib/radixtree_search_impl.h
 create mode 100644 src/test/modules/test_radixtree/.gitignore
 create mode 100644 src/test/modules/test_radixtree/Makefile
 create mode 100644 src/test/modules/test_radixtree/README
 create mode 100644 src/test/modules/test_radixtree/expected/test_radixtree.out
 create mode 100644 src/test/modules/test_radixtree/meson.build
 create mode 100644 src/test/modules/test_radixtree/sql/test_radixtree.sql
 create mode 100644 src/test/modules/test_radixtree/test_radixtree--1.0.sql
 create mode 100644 src/test/modules/test_radixtree/test_radixtree.c
 create mode 100644 src/test/modules/test_radixtree/test_radixtree.control

diff --git a/src/backend/utils/mmgr/dsa.c b/src/backend/utils/mmgr/dsa.c
index f5a62061a3..80555aefff 100644
--- a/src/backend/utils/mmgr/dsa.c
+++ b/src/backend/utils/mmgr/dsa.c
@@ -1024,6 +1024,18 @@ dsa_set_size_limit(dsa_area *area, size_t limit)
 	LWLockRelease(DSA_AREA_LOCK(area));
 }
 
+size_t
+dsa_get_total_size(dsa_area *area)
+{
+	size_t		size;
+
+	LWLockAcquire(DSA_AREA_LOCK(area), LW_SHARED);
+	size = area->control->total_segment_size;
+	LWLockRelease(DSA_AREA_LOCK(area));
+
+	return size;
+}
+
 /*
  * Aggressively free all spare memory in the hope of returning DSM segments to
  * the operating system.
diff --git a/src/include/lib/radixtree.h b/src/include/lib/radixtree.h
new file mode 100644
index 0000000000..e546bd705c
--- /dev/null
+++ b/src/include/lib/radixtree.h
@@ -0,0 +1,2516 @@
+/*-------------------------------------------------------------------------
+ *
+ * radixtree.h
+ *		Template for adaptive radix tree.
+ *
+ * This module employs the idea from the paper "The Adaptive Radix Tree: ARTful
+ * Indexing for Main-Memory Databases" by Viktor Leis, Alfons Kemper, and Thomas
+ * Neumann, 2013. The radix tree uses adaptive node sizes, a small number of node
+ * types, each with a different numbers of elements. Depending on the number of
+ * children, the appropriate node type is used.
+ *
+ * WIP: notes about traditional radix tree trading off span vs height...
+ *
+ * There are two kinds of nodes, inner nodes and leaves. Inner nodes
+ * map partial keys to child pointers.
+ *
+ * The ART paper mentions three ways to implement leaves:
+ *
+ * "- Single-value leaves: The values are stored using an addi-
+ *  tional leaf node type which stores one value.
+ *  - Multi-value leaves: The values are stored in one of four
+ *  different leaf node types, which mirror the structure of
+ *  inner nodes, but contain values instead of pointers.
+ *  - Combined pointer/value slots: If values fit into point-
+ *  ers, no separate node types are necessary. Instead, each
+ *  pointer storage location in an inner node can either
+ *  store a pointer or a value."
+ *
+ * We chose "multi-value leaves" to avoid the additional pointer traversal
+ * required by "single-value leaves"
+ *
+ * For simplicity, the key is assumed to be 64-bit unsigned integer. The
+ * tree doesn't need to contain paths where the highest bytes of all keys
+ * are zero. That way, the tree's height adapts to the distribution of keys.
+ *
+ * TODO: In the future it might be worthwhile to offer configurability of
+ * leaf implementation for different use cases. Single-values leaves would
+ * give more flexibility in key type, including variable-length keys.
+ *
+ * There are some optimizations not yet implemented, particularly path
+ * compression and lazy path expansion.
+ *
+ * To handle concurrency, we use a single reader-writer lock for the radix
+ * tree. The radix tree is exclusively locked during write operations such
+ * as RT_SET() and RT_DELETE(), and shared locked during read operations
+ * such as RT_SEARCH(). An iteration also holds the shared lock on the radix
+ * tree until it is completed.
+ *
+ * TODO: The current locking mechanism is not optimized for high concurrency
+ * with mixed read-write workloads. In the future it might be worthwhile
+ * to replace it with the Optimistic Lock Coupling or ROWEX mentioned in
+ * the paper "The ART of Practical Synchronization" by the same authors as
+ * the ART paper, 2016.
+ *
+ * WIP: the radix tree nodes don't shrink.
+ *
+ * To generate a radix tree and associated functions for a use case several
+ * macros have to be #define'ed before this file is included.  Including
+ * the file #undef's all those, so a new radix tree can be generated
+ * afterwards.
+ * The relevant parameters are:
+ * - RT_PREFIX - prefix for all symbol names generated. A prefix of 'foo'
+ * 	 will result in radix tree type 'foo_radix_tree' and functions like
+ *	 'foo_create'/'foo_free' and so forth.
+ * - RT_DECLARE - if defined function prototypes and type declarations are
+ *	 generated
+ * - RT_DEFINE - if defined function definitions are generated
+ * - RT_SCOPE - in which scope (e.g. extern, static inline) do function
+ *	 declarations reside
+ * - RT_VALUE_TYPE - the type of the value.
+ *
+ * Optional parameters:
+ * - RT_SHMEM - if defined, the radix tree is created in the DSA area
+ *	 so that multiple processes can access it simultaneously.
+ * - RT_DEBUG - if defined add stats tracking and debugging functions
+ *
+ * Interface
+ * ---------
+ *
+ * RT_CREATE		- Create a new, empty radix tree
+ * RT_FREE			- Free the radix tree
+ * RT_SEARCH		- Search a key-value pair
+ * RT_SET			- Set a key-value pair
+ * RT_BEGIN_ITERATE	- Begin iterating through all key-value pairs
+ * RT_ITERATE_NEXT	- Return next key-value pair, if any
+ * RT_END_ITER		- End iteration
+ * RT_MEMORY_USAGE	- Get the memory usage
+ *
+ * Interface for Shared Memory
+ * ---------
+ *
+ * RT_ATTACH		- Attach to the radix tree
+ * RT_DETACH		- Detach from the radix tree
+ * RT_GET_HANDLE	- Return the handle of the radix tree
+ *
+ * Optional Interface
+ * ---------
+ *
+ * RT_DELETE		- Delete a key-value pair. Declared/define if RT_USE_DELETE is defined
+ *
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *	  src/include/lib/radixtree.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "postgres.h"
+
+#include "lib/stringinfo.h"
+#include "miscadmin.h"
+#include "nodes/bitmapset.h"
+#include "port/pg_bitutils.h"
+#include "port/simd.h"
+#include "utils/dsa.h"
+#include "utils/memutils.h"
+
+/* helpers */
+#define RT_MAKE_PREFIX(a) CppConcat(a,_)
+#define RT_MAKE_NAME(name) RT_MAKE_NAME_(RT_MAKE_PREFIX(RT_PREFIX),name)
+#define RT_MAKE_NAME_(a,b) CppConcat(a,b)
+
+/* function declarations */
+#define RT_CREATE RT_MAKE_NAME(create)
+#define RT_FREE RT_MAKE_NAME(free)
+#define RT_SEARCH RT_MAKE_NAME(search)
+#ifdef RT_SHMEM
+#define RT_ATTACH RT_MAKE_NAME(attach)
+#define RT_DETACH RT_MAKE_NAME(detach)
+#define RT_GET_HANDLE RT_MAKE_NAME(get_handle)
+#endif
+#define RT_SET RT_MAKE_NAME(set)
+#define RT_BEGIN_ITERATE RT_MAKE_NAME(begin_iterate)
+#define RT_ITERATE_NEXT RT_MAKE_NAME(iterate_next)
+#define RT_END_ITERATE RT_MAKE_NAME(end_iterate)
+#ifdef RT_USE_DELETE
+#define RT_DELETE RT_MAKE_NAME(delete)
+#endif
+#define RT_MEMORY_USAGE RT_MAKE_NAME(memory_usage)
+#ifdef RT_DEBUG
+#define RT_DUMP RT_MAKE_NAME(dump)
+#define RT_DUMP_NODE RT_MAKE_NAME(dump_node)
+#define RT_DUMP_SEARCH RT_MAKE_NAME(dump_search)
+#define RT_STATS RT_MAKE_NAME(stats)
+#endif
+
+/* internal helper functions (no externally visible prototypes) */
+#define RT_NEW_ROOT RT_MAKE_NAME(new_root)
+#define RT_ALLOC_NODE RT_MAKE_NAME(alloc_node)
+#define RT_INIT_NODE RT_MAKE_NAME(init_node)
+#define RT_FREE_NODE RT_MAKE_NAME(free_node)
+#define RT_FREE_RECURSE RT_MAKE_NAME(free_recurse)
+#define RT_EXTEND RT_MAKE_NAME(extend)
+#define RT_SET_EXTEND RT_MAKE_NAME(set_extend)
+#define RT_SWITCH_NODE_KIND RT_MAKE_NAME(grow_node_kind)
+#define RT_COPY_NODE RT_MAKE_NAME(copy_node)
+#define RT_REPLACE_NODE RT_MAKE_NAME(replace_node)
+#define RT_PTR_GET_LOCAL RT_MAKE_NAME(ptr_get_local)
+#define RT_PTR_ALLOC_IS_VALID RT_MAKE_NAME(ptr_stored_is_valid)
+#define RT_NODE_3_SEARCH_EQ RT_MAKE_NAME(node_3_search_eq)
+#define RT_NODE_32_SEARCH_EQ RT_MAKE_NAME(node_32_search_eq)
+#define RT_NODE_3_GET_INSERTPOS RT_MAKE_NAME(node_3_get_insertpos)
+#define RT_NODE_32_GET_INSERTPOS RT_MAKE_NAME(node_32_get_insertpos)
+#define RT_CHUNK_CHILDREN_ARRAY_SHIFT RT_MAKE_NAME(chunk_children_array_shift)
+#define RT_CHUNK_VALUES_ARRAY_SHIFT RT_MAKE_NAME(chunk_values_array_shift)
+#define RT_CHUNK_CHILDREN_ARRAY_DELETE RT_MAKE_NAME(chunk_children_array_delete)
+#define RT_CHUNK_VALUES_ARRAY_DELETE RT_MAKE_NAME(chunk_values_array_delete)
+#define RT_CHUNK_CHILDREN_ARRAY_COPY RT_MAKE_NAME(chunk_children_array_copy)
+#define RT_CHUNK_VALUES_ARRAY_COPY RT_MAKE_NAME(chunk_values_array_copy)
+#define RT_NODE_125_IS_CHUNK_USED RT_MAKE_NAME(node_125_is_chunk_used)
+#define RT_NODE_INNER_125_GET_CHILD RT_MAKE_NAME(node_inner_125_get_child)
+#define RT_NODE_LEAF_125_GET_VALUE RT_MAKE_NAME(node_leaf_125_get_value)
+#define RT_NODE_INNER_256_IS_CHUNK_USED RT_MAKE_NAME(node_inner_256_is_chunk_used)
+#define RT_NODE_LEAF_256_IS_CHUNK_USED RT_MAKE_NAME(node_leaf_256_is_chunk_used)
+#define RT_NODE_INNER_256_GET_CHILD RT_MAKE_NAME(node_inner_256_get_child)
+#define RT_NODE_LEAF_256_GET_VALUE RT_MAKE_NAME(node_leaf_256_get_value)
+#define RT_NODE_INNER_256_SET RT_MAKE_NAME(node_inner_256_set)
+#define RT_NODE_LEAF_256_SET RT_MAKE_NAME(node_leaf_256_set)
+#define RT_NODE_INNER_256_DELETE RT_MAKE_NAME(node_inner_256_delete)
+#define RT_NODE_LEAF_256_DELETE RT_MAKE_NAME(node_leaf_256_delete)
+#define RT_KEY_GET_SHIFT RT_MAKE_NAME(key_get_shift)
+#define RT_SHIFT_GET_MAX_VAL RT_MAKE_NAME(shift_get_max_val)
+#define RT_NODE_SEARCH_INNER RT_MAKE_NAME(node_search_inner)
+#define RT_NODE_SEARCH_LEAF RT_MAKE_NAME(node_search_leaf)
+#define RT_NODE_UPDATE_INNER RT_MAKE_NAME(node_update_inner)
+#define RT_NODE_DELETE_INNER RT_MAKE_NAME(node_delete_inner)
+#define RT_NODE_DELETE_LEAF RT_MAKE_NAME(node_delete_leaf)
+#define RT_NODE_INSERT_INNER RT_MAKE_NAME(node_insert_inner)
+#define RT_NODE_INSERT_LEAF RT_MAKE_NAME(node_insert_leaf)
+#define RT_NODE_INNER_ITERATE_NEXT RT_MAKE_NAME(node_inner_iterate_next)
+#define RT_NODE_LEAF_ITERATE_NEXT RT_MAKE_NAME(node_leaf_iterate_next)
+#define RT_UPDATE_ITER_STACK RT_MAKE_NAME(update_iter_stack)
+#define RT_ITER_UPDATE_KEY RT_MAKE_NAME(iter_update_key)
+#define RT_VERIFY_NODE RT_MAKE_NAME(verify_node)
+
+/* type declarations */
+#define RT_RADIX_TREE RT_MAKE_NAME(radix_tree)
+#define RT_RADIX_TREE_CONTROL RT_MAKE_NAME(radix_tree_control)
+#define RT_ITER RT_MAKE_NAME(iter)
+#ifdef RT_SHMEM
+#define RT_HANDLE RT_MAKE_NAME(handle)
+#endif
+#define RT_NODE RT_MAKE_NAME(node)
+#define RT_NODE_ITER RT_MAKE_NAME(node_iter)
+#define RT_NODE_BASE_3 RT_MAKE_NAME(node_base_3)
+#define RT_NODE_BASE_32 RT_MAKE_NAME(node_base_32)
+#define RT_NODE_BASE_125 RT_MAKE_NAME(node_base_125)
+#define RT_NODE_BASE_256 RT_MAKE_NAME(node_base_256)
+#define RT_NODE_INNER_3 RT_MAKE_NAME(node_inner_3)
+#define RT_NODE_INNER_32 RT_MAKE_NAME(node_inner_32)
+#define RT_NODE_INNER_125 RT_MAKE_NAME(node_inner_125)
+#define RT_NODE_INNER_256 RT_MAKE_NAME(node_inner_256)
+#define RT_NODE_LEAF_3 RT_MAKE_NAME(node_leaf_3)
+#define RT_NODE_LEAF_32 RT_MAKE_NAME(node_leaf_32)
+#define RT_NODE_LEAF_125 RT_MAKE_NAME(node_leaf_125)
+#define RT_NODE_LEAF_256 RT_MAKE_NAME(node_leaf_256)
+#define RT_SIZE_CLASS RT_MAKE_NAME(size_class)
+#define RT_SIZE_CLASS_ELEM RT_MAKE_NAME(size_class_elem)
+#define RT_SIZE_CLASS_INFO RT_MAKE_NAME(size_class_info)
+#define RT_CLASS_3 RT_MAKE_NAME(class_3)
+#define RT_CLASS_32_MIN RT_MAKE_NAME(class_32_min)
+#define RT_CLASS_32_MAX RT_MAKE_NAME(class_32_max)
+#define RT_CLASS_125 RT_MAKE_NAME(class_125)
+#define RT_CLASS_256 RT_MAKE_NAME(class_256)
+
+/* generate forward declarations necessary to use the radix tree */
+#ifdef RT_DECLARE
+
+typedef struct RT_RADIX_TREE RT_RADIX_TREE;
+typedef struct RT_ITER RT_ITER;
+
+#ifdef RT_SHMEM
+typedef dsa_pointer RT_HANDLE;
+#endif
+
+#ifdef RT_SHMEM
+RT_SCOPE RT_RADIX_TREE * RT_CREATE(MemoryContext ctx, dsa_area *dsa, int tranche_id);
+RT_SCOPE RT_RADIX_TREE * RT_ATTACH(dsa_area *dsa, dsa_pointer dp);
+RT_SCOPE void RT_DETACH(RT_RADIX_TREE *tree);
+RT_SCOPE RT_HANDLE RT_GET_HANDLE(RT_RADIX_TREE *tree);
+#else
+RT_SCOPE RT_RADIX_TREE * RT_CREATE(MemoryContext ctx);
+#endif
+RT_SCOPE void RT_FREE(RT_RADIX_TREE *tree);
+
+RT_SCOPE bool RT_SEARCH(RT_RADIX_TREE *tree, uint64 key, RT_VALUE_TYPE *value_p);
+RT_SCOPE bool RT_SET(RT_RADIX_TREE *tree, uint64 key, RT_VALUE_TYPE *value_p);
+#ifdef RT_USE_DELETE
+RT_SCOPE bool RT_DELETE(RT_RADIX_TREE *tree, uint64 key);
+#endif
+
+RT_SCOPE RT_ITER * RT_BEGIN_ITERATE(RT_RADIX_TREE *tree);
+RT_SCOPE bool RT_ITERATE_NEXT(RT_ITER *iter, uint64 *key_p, RT_VALUE_TYPE *value_p);
+RT_SCOPE void RT_END_ITERATE(RT_ITER *iter);
+
+RT_SCOPE uint64 RT_MEMORY_USAGE(RT_RADIX_TREE *tree);
+
+#ifdef RT_DEBUG
+RT_SCOPE void RT_DUMP(RT_RADIX_TREE *tree);
+RT_SCOPE void RT_DUMP_SEARCH(RT_RADIX_TREE *tree, uint64 key);
+RT_SCOPE void RT_STATS(RT_RADIX_TREE *tree);
+#endif
+
+#endif							/* RT_DECLARE */
+
+
+/* generate implementation of the radix tree */
+#ifdef RT_DEFINE
+
+/* The number of bits encoded in one tree level */
+#define RT_NODE_SPAN	BITS_PER_BYTE
+
+/* The number of maximum slots in the node */
+#define RT_NODE_MAX_SLOTS (1 << RT_NODE_SPAN)
+
+/* Mask for extracting a chunk from the key */
+#define RT_CHUNK_MASK ((1 << RT_NODE_SPAN) - 1)
+
+/* Maximum shift the radix tree uses */
+#define RT_MAX_SHIFT	RT_KEY_GET_SHIFT(UINT64_MAX)
+
+/* Tree level the radix tree uses */
+#define RT_MAX_LEVEL	((sizeof(uint64) * BITS_PER_BYTE) / RT_NODE_SPAN)
+
+/*
+ * Number of bits necessary for isset array in the slot-index node.
+ * Since bitmapword can be 64 bits, the only values that make sense
+ * here are 64 and 128.
+ */
+#define RT_SLOT_IDX_LIMIT (RT_NODE_MAX_SLOTS / 2)
+
+/* Invalid index used in node-125 */
+#define RT_INVALID_SLOT_IDX	0xFF
+
+/* Get a chunk from the key */
+#define RT_GET_KEY_CHUNK(key, shift) ((uint8) (((key) >> (shift)) & RT_CHUNK_MASK))
+
+/* For accessing bitmaps */
+#define RT_BM_IDX(x)	((x) / BITS_PER_BITMAPWORD)
+#define RT_BM_BIT(x)	((x) % BITS_PER_BITMAPWORD)
+
+/*
+ * Node kinds
+ *
+ * The different node kinds are what make the tree "adaptive".
+ *
+ * Each node kind is associated with a different datatype and different
+ * search/set/delete/iterate algorithms adapted for its size. The largest
+ * kind, node256 is basically the same as a traditional radix tree,
+ * and would be most wasteful of memory when sparsely populated. The
+ * smaller nodes expend some additional CPU time to enable a smaller
+ * memory footprint.
+ *
+ * XXX There are 4 node kinds, and this should never be increased,
+ * for several reasons:
+ * 1. With 5 or more kinds, gcc tends to use a jump table for switch
+ *    statements.
+ * 2. The 4 kinds can be represented with 2 bits, so we have the option
+ *    in the future to tag the node pointer with the kind, even on
+ *    platforms with 32-bit pointers. This might speed up node traversal
+ *    in trees with highly random node kinds.
+ * 3. We can have multiple size classes per node kind.
+ */
+#define RT_NODE_KIND_3			0x00
+#define RT_NODE_KIND_32			0x01
+#define RT_NODE_KIND_125		0x02
+#define RT_NODE_KIND_256		0x03
+#define RT_NODE_KIND_COUNT		4
+
+/*
+ * Calculate the slab blocksize so that we can allocate at least 32 chunks
+ * from the block.
+ */
+#define RT_SLAB_BLOCK_SIZE(size)	\
+	Max((SLAB_DEFAULT_BLOCK_SIZE / (size)) * (size), (size) * 32)
+
+/* Common type for all nodes types */
+typedef struct RT_NODE
+{
+	/*
+	 * Number of children.  We use uint16 to be able to indicate 256 children
+	 * at the fanout of 8.
+	 */
+	uint16		count;
+
+	/*
+	 * Max capacity for the current size class. Storing this in the
+	 * node enables multiple size classes per node kind.
+	 * Technically, kinds with a single size class don't need this, so we could
+	 * keep this in the individual base types, but the code is simpler this way.
+	 * Note: node256 is unique in that it cannot possibly have more than a
+	 * single size class, so for that kind we store zero, and uint8 is
+	 * sufficient for other kinds.
+	 */
+	uint8		fanout;
+
+	/*
+	 * Shift indicates which part of the key space is represented by this
+	 * node. That is, the key is shifted by 'shift' and the lowest
+	 * RT_NODE_SPAN bits are then represented in chunk.
+	 */
+	uint8		shift;
+
+	/* Node kind, one per search/set algorithm */
+	uint8		kind;
+} RT_NODE;
+
+
+#define RT_PTR_LOCAL RT_NODE *
+
+#ifdef RT_SHMEM
+#define RT_PTR_ALLOC dsa_pointer
+#else
+#define RT_PTR_ALLOC RT_PTR_LOCAL
+#endif
+
+
+#ifdef RT_SHMEM
+#define RT_INVALID_PTR_ALLOC InvalidDsaPointer
+#else
+#define RT_INVALID_PTR_ALLOC NULL
+#endif
+
+#ifdef RT_SHMEM
+#define RT_LOCK_EXCLUSIVE(tree)	LWLockAcquire(&tree->ctl->lock, LW_EXCLUSIVE)
+#define RT_LOCK_SHARED(tree)	LWLockAcquire(&tree->ctl->lock, LW_SHARED)
+#define RT_UNLOCK(tree)			LWLockRelease(&tree->ctl->lock);
+#else
+#define RT_LOCK_EXCLUSIVE(tree)	((void) 0)
+#define RT_LOCK_SHARED(tree)	((void) 0)
+#define RT_UNLOCK(tree)			((void) 0)
+#endif
+
+/*
+ * Inner nodes and leaf nodes have analogous structure. To distinguish
+ * them at runtime, we take advantage of the fact that the key chunk
+ * is accessed by shifting: Inner tree nodes (shift > 0), store the
+ * pointer to its child node in the slot. In leaf nodes (shift == 0),
+ * the slot contains the value corresponding to the key.
+ */
+#define RT_NODE_IS_LEAF(n)			(((RT_PTR_LOCAL) (n))->shift == 0)
+
+#define RT_NODE_MUST_GROW(node) \
+	((node)->base.n.count == (node)->base.n.fanout)
+
+/*
+ * Base type of each node kinds for leaf and inner nodes.
+ * The base types must be a be able to accommodate the largest size
+ * class for variable-sized node kinds.
+ */
+typedef struct RT_NODE_BASE_3
+{
+	RT_NODE		n;
+
+	/* 3 children, for key chunks */
+	uint8		chunks[3];
+} RT_NODE_BASE_3;
+
+typedef struct RT_NODE_BASE_32
+{
+	RT_NODE		n;
+
+	/* 32 children, for key chunks */
+	uint8		chunks[32];
+} RT_NODE_BASE_32;
+
+/*
+ * node-125 uses slot_idx array, an array of RT_NODE_MAX_SLOTS length
+ * to store indexes into a second array that contains the values (or
+ * child pointers).
+ */
+typedef struct RT_NODE_BASE_125
+{
+	RT_NODE		n;
+
+	/* The index of slots for each fanout */
+	uint8		slot_idxs[RT_NODE_MAX_SLOTS];
+
+	/* bitmap to track which slots are in use */
+	bitmapword		isset[RT_BM_IDX(RT_SLOT_IDX_LIMIT)];
+} RT_NODE_BASE_125;
+
+typedef struct RT_NODE_BASE_256
+{
+	RT_NODE		n;
+} RT_NODE_BASE_256;
+
+/*
+ * Inner and leaf nodes.
+ *
+ * These are separate because the value type might be different than
+ * something fitting into a pointer-width type.
+ */
+typedef struct RT_NODE_INNER_3
+{
+	RT_NODE_BASE_3 base;
+
+	/* number of children depends on size class */
+	RT_PTR_ALLOC children[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_INNER_3;
+
+typedef struct RT_NODE_LEAF_3
+{
+	RT_NODE_BASE_3 base;
+
+	/* number of values depends on size class */
+	RT_VALUE_TYPE	values[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_LEAF_3;
+
+typedef struct RT_NODE_INNER_32
+{
+	RT_NODE_BASE_32 base;
+
+	/* number of children depends on size class */
+	RT_PTR_ALLOC children[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_INNER_32;
+
+typedef struct RT_NODE_LEAF_32
+{
+	RT_NODE_BASE_32 base;
+
+	/* number of values depends on size class */
+	RT_VALUE_TYPE	values[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_LEAF_32;
+
+typedef struct RT_NODE_INNER_125
+{
+	RT_NODE_BASE_125 base;
+
+	/* number of children depends on size class */
+	RT_PTR_ALLOC children[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_INNER_125;
+
+typedef struct RT_NODE_LEAF_125
+{
+	RT_NODE_BASE_125 base;
+
+	/* number of values depends on size class */
+	RT_VALUE_TYPE	values[FLEXIBLE_ARRAY_MEMBER];
+} RT_NODE_LEAF_125;
+
+/*
+ * node-256 is the largest node type. This node has an array
+ * for directly storing values (or child pointers in inner nodes).
+ * Unlike other node kinds, it's array size is by definition
+ * fixed.
+ */
+typedef struct RT_NODE_INNER_256
+{
+	RT_NODE_BASE_256 base;
+
+	/* Slots for 256 children */
+	RT_PTR_ALLOC children[RT_NODE_MAX_SLOTS];
+} RT_NODE_INNER_256;
+
+typedef struct RT_NODE_LEAF_256
+{
+	RT_NODE_BASE_256 base;
+
+	/*
+	 * Unlike with inner256, zero is a valid value here, so we use a
+	 * bitmap to track which slots are in use.
+	 */
+	bitmapword	isset[RT_BM_IDX(RT_NODE_MAX_SLOTS)];
+
+	/* Slots for 256 values */
+	RT_VALUE_TYPE	values[RT_NODE_MAX_SLOTS];
+} RT_NODE_LEAF_256;
+
+/*
+ * Node size classes
+ *
+ * Nodes of different kinds necessarily belong to different size classes.
+ * The main innovation in our implementation compared to the ART paper
+ * is decoupling the notion of size class from kind.
+ *
+ * The size classes within a given node kind have the same underlying
+ * type, but a variable number of children/values. This is possible
+ * because the base type contains small fixed data structures that
+ * work the same way regardless of how full the node is. We store the
+ * node's allocated capacity in the "fanout" member of RT_NODE, to allow
+ * runtime introspection.
+ *
+ * Growing from one node kind to another requires special code for each
+ * case, but growing from one size class to another within the same kind
+ * is basically just allocate + memcpy.
+ *
+ * The size classes have been chosen so that inner nodes on platforms
+ * with 64-bit pointers (and leaf nodes when using a 64-bit key) are
+ * equal to or slightly smaller than some DSA size class.
+ */
+typedef enum RT_SIZE_CLASS
+{
+	RT_CLASS_3 = 0,
+	RT_CLASS_32_MIN,
+	RT_CLASS_32_MAX,
+	RT_CLASS_125,
+	RT_CLASS_256
+} RT_SIZE_CLASS;
+
+/* Information for each size class */
+typedef struct RT_SIZE_CLASS_ELEM
+{
+	const char *name;
+	int			fanout;
+
+	/* slab chunk size */
+	Size		inner_size;
+	Size		leaf_size;
+} RT_SIZE_CLASS_ELEM;
+
+static const RT_SIZE_CLASS_ELEM RT_SIZE_CLASS_INFO[] = {
+	[RT_CLASS_3] = {
+		.name = "radix tree node 3",
+		.fanout = 3,
+		.inner_size = sizeof(RT_NODE_INNER_3) + 3 * sizeof(RT_PTR_ALLOC),
+		.leaf_size = sizeof(RT_NODE_LEAF_3) + 3 * sizeof(RT_VALUE_TYPE),
+	},
+	[RT_CLASS_32_MIN] = {
+		.name = "radix tree node 15",
+		.fanout = 15,
+		.inner_size = sizeof(RT_NODE_INNER_32) + 15 * sizeof(RT_PTR_ALLOC),
+		.leaf_size = sizeof(RT_NODE_LEAF_32) + 15 * sizeof(RT_VALUE_TYPE),
+	},
+	[RT_CLASS_32_MAX] = {
+		.name = "radix tree node 32",
+		.fanout = 32,
+		.inner_size = sizeof(RT_NODE_INNER_32) + 32 * sizeof(RT_PTR_ALLOC),
+		.leaf_size = sizeof(RT_NODE_LEAF_32) + 32 * sizeof(RT_VALUE_TYPE),
+	},
+	[RT_CLASS_125] = {
+		.name = "radix tree node 125",
+		.fanout = 125,
+		.inner_size = sizeof(RT_NODE_INNER_125) + 125 * sizeof(RT_PTR_ALLOC),
+		.leaf_size = sizeof(RT_NODE_LEAF_125) + 125 * sizeof(RT_VALUE_TYPE),
+	},
+	[RT_CLASS_256] = {
+		.name = "radix tree node 256",
+		.fanout = 256,
+		.inner_size = sizeof(RT_NODE_INNER_256),
+		.leaf_size = sizeof(RT_NODE_LEAF_256),
+	},
+};
+
+#define RT_SIZE_CLASS_COUNT lengthof(RT_SIZE_CLASS_INFO)
+
+#ifdef RT_SHMEM
+/* A magic value used to identify our radix tree */
+#define RT_RADIX_TREE_MAGIC 0x54A48167
+#endif
+
+/* Contains the actual tree and ancillary info */
+// WIP: this name is a bit strange
+typedef struct RT_RADIX_TREE_CONTROL
+{
+#ifdef RT_SHMEM
+	RT_HANDLE	handle;
+	uint32		magic;
+	LWLock		lock;
+#endif
+
+	RT_PTR_ALLOC root;
+	uint64		max_val;
+	uint64		num_keys;
+
+	/* statistics */
+#ifdef RT_DEBUG
+	int32		cnt[RT_SIZE_CLASS_COUNT];
+#endif
+} RT_RADIX_TREE_CONTROL;
+
+/* Entry point for allocating and accessing the tree */
+typedef struct RT_RADIX_TREE
+{
+	MemoryContext context;
+
+	/* pointing to either local memory or DSA */
+	RT_RADIX_TREE_CONTROL *ctl;
+
+#ifdef RT_SHMEM
+	dsa_area   *dsa;
+#else
+	MemoryContextData *inner_slabs[RT_SIZE_CLASS_COUNT];
+	MemoryContextData *leaf_slabs[RT_SIZE_CLASS_COUNT];
+#endif
+} RT_RADIX_TREE;
+
+/*
+ * Iteration support.
+ *
+ * Iterating the radix tree returns each pair of key and value in the ascending
+ * order of the key. To support this, the we iterate nodes of each level.
+ *
+ * RT_NODE_ITER struct is used to track the iteration within a node.
+ *
+ * RT_ITER is the struct for iteration of the radix tree, and uses RT_NODE_ITER
+ * in order to track the iteration of each level. During iteration, we also
+ * construct the key whenever updating the node iteration information, e.g., when
+ * advancing the current index within the node or when moving to the next node
+ * at the same level.
+ *
+ * XXX: Currently we allow only one process to do iteration. Therefore, rt_node_iter
+ * has the local pointers to nodes, rather than RT_PTR_ALLOC.
+ * We need either a safeguard to disallow other processes to begin the iteration
+ * while one process is doing or to allow multiple processes to do the iteration.
+ */
+typedef struct RT_NODE_ITER
+{
+	RT_PTR_LOCAL node;			/* current node being iterated */
+	int			current_idx;	/* current position. -1 for initial value */
+} RT_NODE_ITER;
+
+typedef struct RT_ITER
+{
+	RT_RADIX_TREE *tree;
+
+	/* Track the iteration on nodes of each level */
+	RT_NODE_ITER stack[RT_MAX_LEVEL];
+	int			stack_len;
+
+	/* The key is constructed during iteration */
+	uint64		key;
+} RT_ITER;
+
+
+static void RT_NODE_INSERT_INNER(RT_RADIX_TREE *tree, RT_PTR_LOCAL parent, RT_PTR_ALLOC stored_node, RT_PTR_LOCAL node,
+								 uint64 key, RT_PTR_ALLOC child);
+static bool RT_NODE_INSERT_LEAF(RT_RADIX_TREE *tree, RT_PTR_LOCAL parent, RT_PTR_ALLOC stored_node, RT_PTR_LOCAL node,
+								uint64 key, RT_VALUE_TYPE *value_p);
+
+/* verification (available only with assertion) */
+static void RT_VERIFY_NODE(RT_PTR_LOCAL node);
+
+/* Get the local address of an allocated node */
+static inline RT_PTR_LOCAL
+RT_PTR_GET_LOCAL(RT_RADIX_TREE *tree, RT_PTR_ALLOC node)
+{
+#ifdef RT_SHMEM
+	return dsa_get_address(tree->dsa, (dsa_pointer) node);
+#else
+	return node;
+#endif
+}
+
+static inline bool
+RT_PTR_ALLOC_IS_VALID(RT_PTR_ALLOC ptr)
+{
+#ifdef RT_SHMEM
+	return DsaPointerIsValid(ptr);
+#else
+	return PointerIsValid(ptr);
+#endif
+}
+
+/*
+ * Return index of the first element in the node's chunk array that equals
+ * 'chunk'. Return -1 if there is no such element.
+ */
+static inline int
+RT_NODE_3_SEARCH_EQ(RT_NODE_BASE_3 *node, uint8 chunk)
+{
+	int			idx = -1;
+
+	for (int i = 0; i < node->n.count; i++)
+	{
+		if (node->chunks[i] == chunk)
+		{
+			idx = i;
+			break;
+		}
+	}
+
+	return idx;
+}
+
+/*
+ * Return index of the chunk and slot arrays for inserting into the node,
+ * such that the chunk array remains ordered.
+ */
+static inline int
+RT_NODE_3_GET_INSERTPOS(RT_NODE_BASE_3 *node, uint8 chunk)
+{
+	int			idx;
+
+	for (idx = 0; idx < node->n.count; idx++)
+	{
+		if (node->chunks[idx] >= chunk)
+			break;
+	}
+
+	return idx;
+}
+
+/*
+ * Return index of the first element in the node's chunk array that equals
+ * 'chunk'. Return -1 if there is no such element.
+ */
+static inline int
+RT_NODE_32_SEARCH_EQ(RT_NODE_BASE_32 *node, uint8 chunk)
+{
+	int			count = node->n.count;
+#ifndef USE_NO_SIMD
+	Vector8		spread_chunk;
+	Vector8		haystack1;
+	Vector8		haystack2;
+	Vector8		cmp1;
+	Vector8		cmp2;
+	uint32		bitfield;
+	int			index_simd = -1;
+#endif
+
+#if defined(USE_NO_SIMD) || defined(USE_ASSERT_CHECKING)
+	int			index = -1;
+
+	for (int i = 0; i < count; i++)
+	{
+		if (node->chunks[i] == chunk)
+		{
+			index = i;
+			break;
+		}
+	}
+#endif
+
+#ifndef USE_NO_SIMD
+	/* replicate the search key */
+	spread_chunk = vector8_broadcast(chunk);
+
+	/* compare to all 32 keys stored in the node */
+	vector8_load(&haystack1, &node->chunks[0]);
+	vector8_load(&haystack2, &node->chunks[sizeof(Vector8)]);
+	cmp1 = vector8_eq(spread_chunk, haystack1);
+	cmp2 = vector8_eq(spread_chunk, haystack2);
+
+	/* convert comparison to a bitfield */
+	bitfield = vector8_highbit_mask(cmp1) | (vector8_highbit_mask(cmp2) << sizeof(Vector8));
+
+	/* mask off invalid entries */
+	bitfield &= ((UINT64CONST(1) << count) - 1);
+
+	/* convert bitfield to index by counting trailing zeros */
+	if (bitfield)
+		index_simd = pg_rightmost_one_pos32(bitfield);
+
+	Assert(index_simd == index);
+	return index_simd;
+#else
+	return index;
+#endif
+}
+
+/*
+ * Return index of the chunk and slot arrays for inserting into the node,
+ * such that the chunk array remains ordered.
+ */
+static inline int
+RT_NODE_32_GET_INSERTPOS(RT_NODE_BASE_32 *node, uint8 chunk)
+{
+	int			count = node->n.count;
+#ifndef USE_NO_SIMD
+	Vector8		spread_chunk;
+	Vector8		haystack1;
+	Vector8		haystack2;
+	Vector8		cmp1;
+	Vector8		cmp2;
+	Vector8		min1;
+	Vector8		min2;
+	uint32		bitfield;
+	int			index_simd;
+#endif
+
+#if defined(USE_NO_SIMD) || defined(USE_ASSERT_CHECKING)
+	int			index;
+
+	for (index = 0; index < count; index++)
+	{
+		/*
+		 * This is coded with '>=' to match what we can do with SIMD,
+		 * with an assert to keep us honest.
+		 */
+		if (node->chunks[index] >= chunk)
+		{
+			Assert(node->chunks[index] != chunk);
+			break;
+		}
+	}
+#endif
+
+#ifndef USE_NO_SIMD
+	/*
+	 * This is a bit more complicated than RT_NODE_32_SEARCH_EQ(), because
+	 * no unsigned uint8 comparison instruction exists, at least for SSE2. So
+	 * we need to play some trickery using vector8_min() to effectively get
+	 * >=. There'll never be any equal elements in current uses, but that's
+	 * what we get here...
+	 */
+	spread_chunk = vector8_broadcast(chunk);
+	vector8_load(&haystack1, &node->chunks[0]);
+	vector8_load(&haystack2, &node->chunks[sizeof(Vector8)]);
+	min1 = vector8_min(spread_chunk, haystack1);
+	min2 = vector8_min(spread_chunk, haystack2);
+	cmp1 = vector8_eq(spread_chunk, min1);
+	cmp2 = vector8_eq(spread_chunk, min2);
+	bitfield = vector8_highbit_mask(cmp1) | (vector8_highbit_mask(cmp2) << sizeof(Vector8));
+	bitfield &= ((UINT64CONST(1) << count) - 1);
+
+	if (bitfield)
+		index_simd = pg_rightmost_one_pos32(bitfield);
+	else
+		index_simd = count;
+
+	Assert(index_simd == index);
+	return index_simd;
+#else
+	return index;
+#endif
+}
+
+
+/*
+ * Functions to manipulate both chunks array and children/values array.
+ * These are used for node-3 and node-32.
+ */
+
+/* Shift the elements right at 'idx' by one */
+static inline void
+RT_CHUNK_CHILDREN_ARRAY_SHIFT(uint8 *chunks, RT_PTR_ALLOC *children, int count, int idx)
+{
+	memmove(&(chunks[idx + 1]), &(chunks[idx]), sizeof(uint8) * (count - idx));
+	memmove(&(children[idx + 1]), &(children[idx]), sizeof(RT_PTR_ALLOC) * (count - idx));
+}
+
+static inline void
+RT_CHUNK_VALUES_ARRAY_SHIFT(uint8 *chunks, RT_VALUE_TYPE *values, int count, int idx)
+{
+	memmove(&(chunks[idx + 1]), &(chunks[idx]), sizeof(uint8) * (count - idx));
+	memmove(&(values[idx + 1]), &(values[idx]), sizeof(RT_VALUE_TYPE) * (count - idx));
+}
+
+/* Delete the element at 'idx' */
+static inline void
+RT_CHUNK_CHILDREN_ARRAY_DELETE(uint8 *chunks, RT_PTR_ALLOC *children, int count, int idx)
+{
+	memmove(&(chunks[idx]), &(chunks[idx + 1]), sizeof(uint8) * (count - idx - 1));
+	memmove(&(children[idx]), &(children[idx + 1]), sizeof(RT_PTR_ALLOC) * (count - idx - 1));
+}
+
+static inline void
+RT_CHUNK_VALUES_ARRAY_DELETE(uint8 *chunks, RT_VALUE_TYPE *values, int count, int idx)
+{
+	memmove(&(chunks[idx]), &(chunks[idx + 1]), sizeof(uint8) * (count - idx - 1));
+	memmove(&(values[idx]), &(values[idx + 1]), sizeof(RT_VALUE_TYPE) * (count - idx - 1));
+}
+
+/* Copy both chunks and children/values arrays */
+static inline void
+RT_CHUNK_CHILDREN_ARRAY_COPY(uint8 *src_chunks, RT_PTR_ALLOC *src_children,
+						  uint8 *dst_chunks, RT_PTR_ALLOC *dst_children)
+{
+	const int fanout = RT_SIZE_CLASS_INFO[RT_CLASS_3].fanout;
+	const Size chunk_size = sizeof(uint8) * fanout;
+	const Size children_size = sizeof(RT_PTR_ALLOC) * fanout;
+
+	memcpy(dst_chunks, src_chunks, chunk_size);
+	memcpy(dst_children, src_children, children_size);
+}
+
+static inline void
+RT_CHUNK_VALUES_ARRAY_COPY(uint8 *src_chunks, RT_VALUE_TYPE *src_values,
+						uint8 *dst_chunks, RT_VALUE_TYPE *dst_values)
+{
+	const int fanout = RT_SIZE_CLASS_INFO[RT_CLASS_3].fanout;
+	const Size chunk_size = sizeof(uint8) * fanout;
+	const Size values_size = sizeof(RT_VALUE_TYPE) * fanout;
+
+	memcpy(dst_chunks, src_chunks, chunk_size);
+	memcpy(dst_values, src_values, values_size);
+}
+
+/* Functions to manipulate inner and leaf node-125 */
+
+/* Does the given chunk in the node has the value? */
+static inline bool
+RT_NODE_125_IS_CHUNK_USED(RT_NODE_BASE_125 *node, uint8 chunk)
+{
+	return node->slot_idxs[chunk] != RT_INVALID_SLOT_IDX;
+}
+
+static inline RT_PTR_ALLOC
+RT_NODE_INNER_125_GET_CHILD(RT_NODE_INNER_125 *node, uint8 chunk)
+{
+	Assert(!RT_NODE_IS_LEAF(node));
+	return node->children[node->base.slot_idxs[chunk]];
+}
+
+static inline RT_VALUE_TYPE
+RT_NODE_LEAF_125_GET_VALUE(RT_NODE_LEAF_125 *node, uint8 chunk)
+{
+	Assert(RT_NODE_IS_LEAF(node));
+	Assert(((RT_NODE_BASE_125 *) node)->slot_idxs[chunk] != RT_INVALID_SLOT_IDX);
+	return node->values[node->base.slot_idxs[chunk]];
+}
+
+/* Functions to manipulate inner and leaf node-256 */
+
+/* Return true if the slot corresponding to the given chunk is in use */
+static inline bool
+RT_NODE_INNER_256_IS_CHUNK_USED(RT_NODE_INNER_256 *node, uint8 chunk)
+{
+	Assert(!RT_NODE_IS_LEAF(node));
+	return node->children[chunk] != RT_INVALID_PTR_ALLOC;
+}
+
+static inline bool
+RT_NODE_LEAF_256_IS_CHUNK_USED(RT_NODE_LEAF_256 *node, uint8 chunk)
+{
+	int			idx = RT_BM_IDX(chunk);
+	int			bitnum = RT_BM_BIT(chunk);
+
+	Assert(RT_NODE_IS_LEAF(node));
+	return (node->isset[idx] & ((bitmapword) 1 << bitnum)) != 0;
+}
+
+static inline RT_PTR_ALLOC
+RT_NODE_INNER_256_GET_CHILD(RT_NODE_INNER_256 *node, uint8 chunk)
+{
+	Assert(!RT_NODE_IS_LEAF(node));
+	Assert(RT_NODE_INNER_256_IS_CHUNK_USED(node, chunk));
+	return node->children[chunk];
+}
+
+static inline RT_VALUE_TYPE
+RT_NODE_LEAF_256_GET_VALUE(RT_NODE_LEAF_256 *node, uint8 chunk)
+{
+	Assert(RT_NODE_IS_LEAF(node));
+	Assert(RT_NODE_LEAF_256_IS_CHUNK_USED(node, chunk));
+	return node->values[chunk];
+}
+
+/* Set the child in the node-256 */
+static inline void
+RT_NODE_INNER_256_SET(RT_NODE_INNER_256 *node, uint8 chunk, RT_PTR_ALLOC child)
+{
+	Assert(!RT_NODE_IS_LEAF(node));
+	node->children[chunk] = child;
+}
+
+/* Set the value in the node-256 */
+static inline void
+RT_NODE_LEAF_256_SET(RT_NODE_LEAF_256 *node, uint8 chunk, RT_VALUE_TYPE value)
+{
+	int			idx = RT_BM_IDX(chunk);
+	int			bitnum = RT_BM_BIT(chunk);
+
+	Assert(RT_NODE_IS_LEAF(node));
+	node->isset[idx] |= ((bitmapword) 1 << bitnum);
+	node->values[chunk] = value;
+}
+
+/* Set the slot at the given chunk position */
+static inline void
+RT_NODE_INNER_256_DELETE(RT_NODE_INNER_256 *node, uint8 chunk)
+{
+	Assert(!RT_NODE_IS_LEAF(node));
+	node->children[chunk] = RT_INVALID_PTR_ALLOC;
+}
+
+static inline void
+RT_NODE_LEAF_256_DELETE(RT_NODE_LEAF_256 *node, uint8 chunk)
+{
+	int			idx = RT_BM_IDX(chunk);
+	int			bitnum = RT_BM_BIT(chunk);
+
+	Assert(RT_NODE_IS_LEAF(node));
+	node->isset[idx] &= ~((bitmapword) 1 << bitnum);
+}
+
+/*
+ * Return the largest shift that will allowing storing the given key.
+ */
+static inline int
+RT_KEY_GET_SHIFT(uint64 key)
+{
+	if (key == 0)
+		return 0;
+	else
+		return (pg_leftmost_one_pos64(key) / RT_NODE_SPAN) * RT_NODE_SPAN;
+}
+
+/*
+ * Return the max value that can be stored in the tree with the given shift.
+ */
+static uint64
+RT_SHIFT_GET_MAX_VAL(int shift)
+{
+	if (shift == RT_MAX_SHIFT)
+		return UINT64_MAX;
+
+	return (UINT64CONST(1) << (shift + RT_NODE_SPAN)) - 1;
+}
+
+/*
+ * Allocate a new node with the given node kind.
+ */
+static RT_PTR_ALLOC
+RT_ALLOC_NODE(RT_RADIX_TREE *tree, RT_SIZE_CLASS size_class, bool is_leaf)
+{
+	RT_PTR_ALLOC allocnode;
+	size_t allocsize;
+
+	if (is_leaf)
+		allocsize = RT_SIZE_CLASS_INFO[size_class].leaf_size;
+	else
+		allocsize = RT_SIZE_CLASS_INFO[size_class].inner_size;
+
+#ifdef RT_SHMEM
+	allocnode = dsa_allocate(tree->dsa, allocsize);
+#else
+	if (is_leaf)
+		allocnode = (RT_PTR_ALLOC) MemoryContextAlloc(tree->leaf_slabs[size_class],
+													  allocsize);
+	else
+		allocnode = (RT_PTR_ALLOC) MemoryContextAlloc(tree->inner_slabs[size_class],
+													  allocsize);
+#endif
+
+#ifdef RT_DEBUG
+	/* update the statistics */
+	tree->ctl->cnt[size_class]++;
+#endif
+
+	return allocnode;
+}
+
+/* Initialize the node contents */
+static inline void
+RT_INIT_NODE(RT_PTR_LOCAL node, uint8 kind, RT_SIZE_CLASS size_class, bool is_leaf)
+{
+	if (is_leaf)
+		MemSet(node, 0, RT_SIZE_CLASS_INFO[size_class].leaf_size);
+	else
+		MemSet(node, 0, RT_SIZE_CLASS_INFO[size_class].inner_size);
+
+	node->kind = kind;
+
+	if (kind == RT_NODE_KIND_256)
+		/* See comment for the RT_NODE type */
+		Assert(node->fanout == 0);
+	else
+		node->fanout = RT_SIZE_CLASS_INFO[size_class].fanout;
+
+	/* Initialize slot_idxs to invalid values */
+	if (kind == RT_NODE_KIND_125)
+	{
+		RT_NODE_BASE_125 *n125 = (RT_NODE_BASE_125 *) node;
+
+		memset(n125->slot_idxs, RT_INVALID_SLOT_IDX, sizeof(n125->slot_idxs));
+	}
+}
+
+/*
+ * Create a new node as the root. Subordinate nodes will be created during
+ * the insertion.
+ */
+static pg_noinline void
+RT_NEW_ROOT(RT_RADIX_TREE *tree, uint64 key)
+{
+	int			shift = RT_KEY_GET_SHIFT(key);
+	bool		is_leaf = shift == 0;
+	RT_PTR_ALLOC allocnode;
+	RT_PTR_LOCAL newnode;
+
+	allocnode = RT_ALLOC_NODE(tree, RT_CLASS_3, is_leaf);
+	newnode = RT_PTR_GET_LOCAL(tree, allocnode);
+	RT_INIT_NODE(newnode, RT_NODE_KIND_3, RT_CLASS_3, is_leaf);
+	newnode->shift = shift;
+	tree->ctl->max_val = RT_SHIFT_GET_MAX_VAL(shift);
+	tree->ctl->root = allocnode;
+}
+
+static inline void
+RT_COPY_NODE(RT_PTR_LOCAL newnode, RT_PTR_LOCAL oldnode)
+{
+	newnode->shift = oldnode->shift;
+	newnode->count = oldnode->count;
+}
+
+/*
+ * Given a new allocated node and an old node, initalize the new
+ * node with the necessary fields and return its local pointer.
+ */
+static inline RT_PTR_LOCAL
+RT_SWITCH_NODE_KIND(RT_RADIX_TREE *tree, RT_PTR_ALLOC allocnode, RT_PTR_LOCAL node,
+				  uint8 new_kind, uint8 new_class, bool is_leaf)
+{
+	RT_PTR_LOCAL newnode = RT_PTR_GET_LOCAL(tree, allocnode);
+	RT_INIT_NODE(newnode, new_kind, new_class, is_leaf);
+	RT_COPY_NODE(newnode, node);
+
+	return newnode;
+}
+
+/* Free the given node */
+static void
+RT_FREE_NODE(RT_RADIX_TREE *tree, RT_PTR_ALLOC allocnode)
+{
+	/* If we're deleting the root node, make the tree empty */
+	if (tree->ctl->root == allocnode)
+	{
+		tree->ctl->root = RT_INVALID_PTR_ALLOC;
+		tree->ctl->max_val = 0;
+	}
+
+#ifdef RT_DEBUG
+	{
+		int i;
+		RT_PTR_LOCAL node = RT_PTR_GET_LOCAL(tree, allocnode);
+
+		/* update the statistics */
+		for (i = 0; i < RT_SIZE_CLASS_COUNT; i++)
+		{
+			if (node->fanout == RT_SIZE_CLASS_INFO[i].fanout)
+				break;
+		}
+
+		/* fanout of node256 is intentionally 0 */
+		if (i == RT_SIZE_CLASS_COUNT)
+			i = RT_CLASS_256;
+
+		tree->ctl->cnt[i]--;
+		Assert(tree->ctl->cnt[i] >= 0);
+	}
+#endif
+
+#ifdef RT_SHMEM
+	dsa_free(tree->dsa, allocnode);
+#else
+	pfree(allocnode);
+#endif
+}
+
+/* Update the parent's pointer when growing a node */
+static inline void
+RT_NODE_UPDATE_INNER(RT_PTR_LOCAL node, uint64 key, RT_PTR_ALLOC new_child)
+{
+#define RT_ACTION_UPDATE
+#define RT_NODE_LEVEL_INNER
+#include "lib/radixtree_search_impl.h"
+#undef RT_NODE_LEVEL_INNER
+#undef RT_ACTION_UPDATE
+}
+
+/*
+ * Replace old_child with new_child, and free the old one.
+ */
+static inline void
+RT_REPLACE_NODE(RT_RADIX_TREE *tree, RT_PTR_LOCAL parent,
+				RT_PTR_ALLOC stored_old_child, RT_PTR_LOCAL old_child,
+				RT_PTR_ALLOC new_child, uint64 key)
+{
+#ifdef USE_ASSERT_CHECKING
+	RT_PTR_LOCAL new = RT_PTR_GET_LOCAL(tree, new_child);
+
+	Assert(old_child->shift == new->shift);
+	Assert(old_child->count == new->count);
+#endif
+
+	if (parent == old_child)
+	{
+		/* Replace the root node with the new larger node */
+		tree->ctl->root = new_child;
+	}
+	else
+		RT_NODE_UPDATE_INNER(parent, key, new_child);
+
+	RT_FREE_NODE(tree, stored_old_child);
+}
+
+/*
+ * The radix tree doesn't have sufficient height. Extend the radix tree so
+ * it can store the key.
+ */
+static pg_noinline void
+RT_EXTEND(RT_RADIX_TREE *tree, uint64 key)
+{
+	int			target_shift;
+	RT_PTR_LOCAL root = RT_PTR_GET_LOCAL(tree, tree->ctl->root);
+	int			shift = root->shift + RT_NODE_SPAN;
+
+	target_shift = RT_KEY_GET_SHIFT(key);
+
+	/* Grow tree from 'shift' to 'target_shift' */
+	while (shift <= target_shift)
+	{
+		RT_PTR_ALLOC	allocnode;
+		RT_PTR_LOCAL	node;
+		RT_NODE_INNER_3 *n3;
+
+		allocnode = RT_ALLOC_NODE(tree, RT_CLASS_3, true);
+		node = RT_PTR_GET_LOCAL(tree, allocnode);
+		RT_INIT_NODE(node, RT_NODE_KIND_3, RT_CLASS_3, true);
+		node->shift = shift;
+		node->count = 1;
+
+		n3 = (RT_NODE_INNER_3 *) node;
+		n3->base.chunks[0] = 0;
+		n3->children[0] = tree->ctl->root;
+
+		/* Update the root */
+		tree->ctl->root = allocnode;
+
+		shift += RT_NODE_SPAN;
+	}
+
+	tree->ctl->max_val = RT_SHIFT_GET_MAX_VAL(target_shift);
+}
+
+/*
+ * The radix tree doesn't have inner and leaf nodes for given key-value pair.
+ * Insert inner and leaf nodes from 'node' to bottom.
+ */
+static pg_noinline void
+RT_SET_EXTEND(RT_RADIX_TREE *tree, uint64 key, RT_VALUE_TYPE *value_p, RT_PTR_LOCAL parent,
+			  RT_PTR_ALLOC stored_node, RT_PTR_LOCAL node)
+{
+	int			shift = node->shift;
+
+	Assert(RT_PTR_GET_LOCAL(tree, stored_node) == node);
+
+	while (shift >= RT_NODE_SPAN)
+	{
+		RT_PTR_ALLOC allocchild;
+		RT_PTR_LOCAL newchild;
+		int			newshift = shift - RT_NODE_SPAN;
+		bool		is_leaf = newshift == 0;
+
+		allocchild = RT_ALLOC_NODE(tree, RT_CLASS_3, is_leaf);
+		newchild = RT_PTR_GET_LOCAL(tree, allocchild);
+		RT_INIT_NODE(newchild, RT_NODE_KIND_3, RT_CLASS_3, is_leaf);
+		newchild->shift = newshift;
+		RT_NODE_INSERT_INNER(tree, parent, stored_node, node, key, allocchild);
+
+		parent = node;
+		node = newchild;
+		stored_node = allocchild;
+		shift -= RT_NODE_SPAN;
+	}
+
+	RT_NODE_INSERT_LEAF(tree, parent, stored_node, node, key, value_p);
+	tree->ctl->num_keys++;
+}
+
+/*
+ * Search for the child pointer corresponding to 'key' in the given node.
+ *
+ * Return true if the key is found, otherwise return false. On success, the child
+ * pointer is set to child_p.
+ */
+static inline bool
+RT_NODE_SEARCH_INNER(RT_PTR_LOCAL node, uint64 key, RT_PTR_ALLOC *child_p)
+{
+#define RT_NODE_LEVEL_INNER
+#include "lib/radixtree_search_impl.h"
+#undef RT_NODE_LEVEL_INNER
+}
+
+/*
+ * Search for the value corresponding to 'key' in the given node.
+ *
+ * Return true if the key is found, otherwise return false. On success, the pointer
+ * to the value is set to value_p.
+ */
+static inline bool
+RT_NODE_SEARCH_LEAF(RT_PTR_LOCAL node, uint64 key, RT_VALUE_TYPE *value_p)
+{
+#define RT_NODE_LEVEL_LEAF
+#include "lib/radixtree_search_impl.h"
+#undef RT_NODE_LEVEL_LEAF
+}
+
+#ifdef RT_USE_DELETE
+/*
+ * Search for the child pointer corresponding to 'key' in the given node.
+ *
+ * Delete the node and return true if the key is found, otherwise return false.
+ */
+static inline bool
+RT_NODE_DELETE_INNER(RT_PTR_LOCAL node, uint64 key)
+{
+#define RT_NODE_LEVEL_INNER
+#include "lib/radixtree_delete_impl.h"
+#undef RT_NODE_LEVEL_INNER
+}
+
+/*
+ * Search for the value corresponding to 'key' in the given node.
+ *
+ * Delete the node and return true if the key is found, otherwise return false.
+ */
+static inline bool
+RT_NODE_DELETE_LEAF(RT_PTR_LOCAL node, uint64 key)
+{
+#define RT_NODE_LEVEL_LEAF
+#include "lib/radixtree_delete_impl.h"
+#undef RT_NODE_LEVEL_LEAF
+}
+#endif
+
+/*
+ * Insert "child" into "node".
+ *
+ * "parent" is the parent of "node", so the grandparent of the child.
+ * If the node we're inserting into needs to grow, we update the parent's
+ * child pointer with the pointer to the new larger node.
+ */
+static void
+RT_NODE_INSERT_INNER(RT_RADIX_TREE *tree, RT_PTR_LOCAL parent, RT_PTR_ALLOC stored_node, RT_PTR_LOCAL node,
+					uint64 key, RT_PTR_ALLOC child)
+{
+#define RT_NODE_LEVEL_INNER
+#include "lib/radixtree_insert_impl.h"
+#undef RT_NODE_LEVEL_INNER
+}
+
+/* Like RT_NODE_INSERT_INNER, but for leaf nodes */
+static bool
+RT_NODE_INSERT_LEAF(RT_RADIX_TREE *tree, RT_PTR_LOCAL parent, RT_PTR_ALLOC stored_node, RT_PTR_LOCAL node,
+					uint64 key, RT_VALUE_TYPE *value_p)
+{
+#define RT_NODE_LEVEL_LEAF
+#include "lib/radixtree_insert_impl.h"
+#undef RT_NODE_LEVEL_LEAF
+}
+
+/*
+ * Create the radix tree in the given memory context and return it.
+ */
+RT_SCOPE RT_RADIX_TREE *
+#ifdef RT_SHMEM
+RT_CREATE(MemoryContext ctx, dsa_area *dsa, int tranche_id)
+#else
+RT_CREATE(MemoryContext ctx)
+#endif
+{
+	RT_RADIX_TREE *tree;
+	MemoryContext old_ctx;
+#ifdef RT_SHMEM
+	dsa_pointer dp;
+#endif
+
+	old_ctx = MemoryContextSwitchTo(ctx);
+
+	tree = (RT_RADIX_TREE *) palloc0(sizeof(RT_RADIX_TREE));
+	tree->context = ctx;
+
+#ifdef RT_SHMEM
+	tree->dsa = dsa;
+	dp = dsa_allocate0(dsa, sizeof(RT_RADIX_TREE_CONTROL));
+	tree->ctl = (RT_RADIX_TREE_CONTROL *) dsa_get_address(dsa, dp);
+	tree->ctl->handle = dp;
+	tree->ctl->magic = RT_RADIX_TREE_MAGIC;
+	LWLockInitialize(&tree->ctl->lock, tranche_id);
+#else
+	tree->ctl = (RT_RADIX_TREE_CONTROL *) palloc0(sizeof(RT_RADIX_TREE_CONTROL));
+
+	/* Create a slab context for each size class */
+	for (int i = 0; i < RT_SIZE_CLASS_COUNT; i++)
+	{
+		RT_SIZE_CLASS_ELEM size_class = RT_SIZE_CLASS_INFO[i];
+		size_t inner_blocksize = RT_SLAB_BLOCK_SIZE(size_class.inner_size);
+		size_t leaf_blocksize = RT_SLAB_BLOCK_SIZE(size_class.leaf_size);
+
+		tree->inner_slabs[i] = SlabContextCreate(ctx,
+												 size_class.name,
+												 inner_blocksize,
+												 size_class.inner_size);
+		tree->leaf_slabs[i] = SlabContextCreate(ctx,
+												size_class.name,
+												leaf_blocksize,
+												size_class.leaf_size);
+	}
+#endif
+
+	tree->ctl->root = RT_INVALID_PTR_ALLOC;
+
+	MemoryContextSwitchTo(old_ctx);
+
+	return tree;
+}
+
+#ifdef RT_SHMEM
+RT_SCOPE RT_RADIX_TREE *
+RT_ATTACH(dsa_area *dsa, RT_HANDLE handle)
+{
+	RT_RADIX_TREE *tree;
+	dsa_pointer	control;
+
+	tree = (RT_RADIX_TREE *) palloc0(sizeof(RT_RADIX_TREE));
+
+	/* Find the control object in shard memory */
+	control = handle;
+
+	tree->dsa = dsa;
+	tree->ctl = (RT_RADIX_TREE_CONTROL *) dsa_get_address(dsa, control);
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+
+	return tree;
+}
+
+RT_SCOPE void
+RT_DETACH(RT_RADIX_TREE *tree)
+{
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+	pfree(tree);
+}
+
+RT_SCOPE RT_HANDLE
+RT_GET_HANDLE(RT_RADIX_TREE *tree)
+{
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+	return tree->ctl->handle;
+}
+
+/*
+ * Recursively free all nodes allocated to the DSA area.
+ */
+static void
+RT_FREE_RECURSE(RT_RADIX_TREE *tree, RT_PTR_ALLOC ptr)
+{
+	RT_PTR_LOCAL node = RT_PTR_GET_LOCAL(tree, ptr);
+
+	check_stack_depth();
+	CHECK_FOR_INTERRUPTS();
+
+	/* The leaf node doesn't have child pointers */
+	if (RT_NODE_IS_LEAF(node))
+	{
+		dsa_free(tree->dsa, ptr);
+		return;
+	}
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE_INNER_3 *n3 = (RT_NODE_INNER_3 *) node;
+
+				for (int i = 0; i < n3->base.n.count; i++)
+					RT_FREE_RECURSE(tree, n3->children[i]);
+
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				RT_NODE_INNER_32 *n32 = (RT_NODE_INNER_32 *) node;
+
+				for (int i = 0; i < n32->base.n.count; i++)
+					RT_FREE_RECURSE(tree, n32->children[i]);
+
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE_INNER_125 *n125 = (RT_NODE_INNER_125 *) node;
+
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (!RT_NODE_125_IS_CHUNK_USED(&n125->base, i))
+						continue;
+
+					RT_FREE_RECURSE(tree, RT_NODE_INNER_125_GET_CHILD(n125, i));
+				}
+
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				RT_NODE_INNER_256 *n256 = (RT_NODE_INNER_256 *) node;
+
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (!RT_NODE_INNER_256_IS_CHUNK_USED(n256, i))
+						continue;
+
+					RT_FREE_RECURSE(tree, RT_NODE_INNER_256_GET_CHILD(n256, i));
+				}
+
+				break;
+			}
+	}
+
+	/* Free the inner node */
+	dsa_free(tree->dsa, ptr);
+}
+#endif
+
+/*
+ * Free the given radix tree.
+ */
+RT_SCOPE void
+RT_FREE(RT_RADIX_TREE *tree)
+{
+#ifdef RT_SHMEM
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+
+	/* Free all memory used for radix tree nodes */
+	if (RT_PTR_ALLOC_IS_VALID(tree->ctl->root))
+		RT_FREE_RECURSE(tree, tree->ctl->root);
+
+	/*
+	 * Vandalize the control block to help catch programming error where
+	 * other backends access the memory formerly occupied by this radix tree.
+	 */
+	tree->ctl->magic = 0;
+	dsa_free(tree->dsa, tree->ctl->handle);
+#else
+	pfree(tree->ctl);
+
+	for (int i = 0; i < RT_SIZE_CLASS_COUNT; i++)
+	{
+		MemoryContextDelete(tree->inner_slabs[i]);
+		MemoryContextDelete(tree->leaf_slabs[i]);
+	}
+#endif
+
+	pfree(tree);
+}
+
+/*
+ * Set key to value. If the entry already exists, we update its value to 'value'
+ * and return true. Returns false if entry doesn't yet exist.
+ */
+RT_SCOPE bool
+RT_SET(RT_RADIX_TREE *tree, uint64 key, RT_VALUE_TYPE *value_p)
+{
+	int			shift;
+	bool		updated;
+	RT_PTR_LOCAL parent;
+	RT_PTR_ALLOC stored_child;
+	RT_PTR_LOCAL  child;
+
+#ifdef RT_SHMEM
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+#endif
+
+	RT_LOCK_EXCLUSIVE(tree);
+
+	/* Empty tree, create the root */
+	if (!RT_PTR_ALLOC_IS_VALID(tree->ctl->root))
+		RT_NEW_ROOT(tree, key);
+
+	/* Extend the tree if necessary */
+	if (key > tree->ctl->max_val)
+		RT_EXTEND(tree, key);
+
+	stored_child = tree->ctl->root;
+	parent = RT_PTR_GET_LOCAL(tree, stored_child);
+	shift = parent->shift;
+
+	/* Descend the tree until we reach a leaf node */
+	while (shift >= 0)
+	{
+		RT_PTR_ALLOC new_child = RT_INVALID_PTR_ALLOC;
+
+		child = RT_PTR_GET_LOCAL(tree, stored_child);
+
+		if (RT_NODE_IS_LEAF(child))
+			break;
+
+		if (!RT_NODE_SEARCH_INNER(child, key, &new_child))
+		{
+			RT_SET_EXTEND(tree, key, value_p, parent, stored_child, child);
+			RT_UNLOCK(tree);
+			return false;
+		}
+
+		parent = child;
+		stored_child = new_child;
+		shift -= RT_NODE_SPAN;
+	}
+
+	updated = RT_NODE_INSERT_LEAF(tree, parent, stored_child, child, key, value_p);
+
+	/* Update the statistics */
+	if (!updated)
+		tree->ctl->num_keys++;
+
+	RT_UNLOCK(tree);
+	return updated;
+}
+
+/*
+ * Search the given key in the radix tree. Return true if there is the key,
+ * otherwise return false. On success, we set the value to *value_p so it must
+ * not be NULL.
+ */
+RT_SCOPE bool
+RT_SEARCH(RT_RADIX_TREE *tree, uint64 key, RT_VALUE_TYPE *value_p)
+{
+	RT_PTR_LOCAL node;
+	int			shift;
+	bool		found;
+
+#ifdef RT_SHMEM
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+#endif
+	Assert(value_p != NULL);
+
+	RT_LOCK_SHARED(tree);
+
+	if (!RT_PTR_ALLOC_IS_VALID(tree->ctl->root) || key > tree->ctl->max_val)
+	{
+		RT_UNLOCK(tree);
+		return false;
+	}
+
+	node = RT_PTR_GET_LOCAL(tree, tree->ctl->root);
+	shift = node->shift;
+
+	/* Descend the tree until a leaf node */
+	while (shift >= 0)
+	{
+		RT_PTR_ALLOC child = RT_INVALID_PTR_ALLOC;
+
+		if (RT_NODE_IS_LEAF(node))
+			break;
+
+		if (!RT_NODE_SEARCH_INNER(node, key, &child))
+		{
+			RT_UNLOCK(tree);
+			return false;
+		}
+
+		node = RT_PTR_GET_LOCAL(tree, child);
+		shift -= RT_NODE_SPAN;
+	}
+
+	found = RT_NODE_SEARCH_LEAF(node, key, value_p);
+
+	RT_UNLOCK(tree);
+	return found;
+}
+
+#ifdef RT_USE_DELETE
+/*
+ * Delete the given key from the radix tree. Return true if the key is found (and
+ * deleted), otherwise do nothing and return false.
+ */
+RT_SCOPE bool
+RT_DELETE(RT_RADIX_TREE *tree, uint64 key)
+{
+	RT_PTR_LOCAL node;
+	RT_PTR_ALLOC allocnode;
+	RT_PTR_ALLOC stack[RT_MAX_LEVEL] = {0};
+	int			shift;
+	int			level;
+	bool		deleted;
+
+#ifdef RT_SHMEM
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+#endif
+
+	RT_LOCK_EXCLUSIVE(tree);
+
+	if (!RT_PTR_ALLOC_IS_VALID(tree->ctl->root) || key > tree->ctl->max_val)
+	{
+		RT_UNLOCK(tree);
+		return false;
+	}
+
+	/*
+	 * Descend the tree to search the key while building a stack of nodes we
+	 * visited.
+	 */
+	allocnode = tree->ctl->root;
+	node = RT_PTR_GET_LOCAL(tree, allocnode);
+	shift = node->shift;
+	level = -1;
+	while (shift > 0)
+	{
+		RT_PTR_ALLOC child = RT_INVALID_PTR_ALLOC;
+
+		/* Push the current node to the stack */
+		stack[++level] = allocnode;
+		node = RT_PTR_GET_LOCAL(tree, allocnode);
+
+		if (!RT_NODE_SEARCH_INNER(node, key, &child))
+		{
+			RT_UNLOCK(tree);
+			return false;
+		}
+
+		allocnode = child;
+		shift -= RT_NODE_SPAN;
+	}
+
+	/* Delete the key from the leaf node if exists */
+	node = RT_PTR_GET_LOCAL(tree, allocnode);
+	deleted = RT_NODE_DELETE_LEAF(node, key);
+
+	if (!deleted)
+	{
+		/* no key is found in the leaf node */
+		RT_UNLOCK(tree);
+		return false;
+	}
+
+	/* Found the key to delete. Update the statistics */
+	tree->ctl->num_keys--;
+
+	/*
+	 * Return if the leaf node still has keys and we don't need to delete the
+	 * node.
+	 */
+	if (node->count > 0)
+	{
+		RT_UNLOCK(tree);
+		return true;
+	}
+
+	/* Free the empty leaf node */
+	RT_FREE_NODE(tree, allocnode);
+
+	/* Delete the key in inner nodes recursively */
+	while (level >= 0)
+	{
+		allocnode = stack[level--];
+
+		node = RT_PTR_GET_LOCAL(tree, allocnode);
+		deleted = RT_NODE_DELETE_INNER(node, key);
+		Assert(deleted);
+
+		/* If the node didn't become empty, we stop deleting the key */
+		if (node->count > 0)
+			break;
+
+		/* The node became empty */
+		RT_FREE_NODE(tree, allocnode);
+	}
+
+	RT_UNLOCK(tree);
+	return true;
+}
+#endif
+
+static inline void
+RT_ITER_UPDATE_KEY(RT_ITER *iter, uint8 chunk, uint8 shift)
+{
+	iter->key &= ~(((uint64) RT_CHUNK_MASK) << shift);
+	iter->key |= (((uint64) chunk) << shift);
+}
+
+/*
+ * Advance the slot in the inner node. Return the child if exists, otherwise
+ * null.
+ */
+static inline RT_PTR_LOCAL
+RT_NODE_INNER_ITERATE_NEXT(RT_ITER *iter, RT_NODE_ITER *node_iter)
+{
+#define RT_NODE_LEVEL_INNER
+#include "lib/radixtree_iter_impl.h"
+#undef RT_NODE_LEVEL_INNER
+}
+
+/*
+ * Advance the slot in the leaf node. On success, return true and the value
+ * is set to value_p, otherwise return false.
+ */
+static inline bool
+RT_NODE_LEAF_ITERATE_NEXT(RT_ITER *iter, RT_NODE_ITER *node_iter,
+						  RT_VALUE_TYPE *value_p)
+{
+#define RT_NODE_LEVEL_LEAF
+#include "lib/radixtree_iter_impl.h"
+#undef RT_NODE_LEVEL_LEAF
+}
+
+/*
+ * Update each node_iter for inner nodes in the iterator node stack.
+ */
+static void
+RT_UPDATE_ITER_STACK(RT_ITER *iter, RT_PTR_LOCAL from_node, int from)
+{
+	int			level = from;
+	RT_PTR_LOCAL node = from_node;
+
+	for (;;)
+	{
+		RT_NODE_ITER *node_iter = &(iter->stack[level--]);
+
+		node_iter->node = node;
+		node_iter->current_idx = -1;
+
+		/* We don't advance the leaf node iterator here */
+		if (RT_NODE_IS_LEAF(node))
+			return;
+
+		/* Advance to the next slot in the inner node */
+		node = RT_NODE_INNER_ITERATE_NEXT(iter, node_iter);
+
+		/* We must find the first children in the node */
+		Assert(node);
+	}
+}
+
+/*
+ * Create and return the iterator for the given radix tree.
+ *
+ * The radix tree is locked in shared mode during the iteration, so
+ * RT_END_ITERATE needs to be called when finished to release the lock.
+ */
+RT_SCOPE RT_ITER *
+RT_BEGIN_ITERATE(RT_RADIX_TREE *tree)
+{
+	MemoryContext old_ctx;
+	RT_ITER    *iter;
+	RT_PTR_LOCAL root;
+	int			top_level;
+
+	old_ctx = MemoryContextSwitchTo(tree->context);
+
+	iter = (RT_ITER *) palloc0(sizeof(RT_ITER));
+	iter->tree = tree;
+
+	RT_LOCK_SHARED(tree);
+
+	/* empty tree */
+	if (!iter->tree->ctl->root)
+		return iter;
+
+	root = RT_PTR_GET_LOCAL(tree, iter->tree->ctl->root);
+	top_level = root->shift / RT_NODE_SPAN;
+	iter->stack_len = top_level;
+
+	/*
+	 * Descend to the left most leaf node from the root. The key is being
+	 * constructed while descending to the leaf.
+	 */
+	RT_UPDATE_ITER_STACK(iter, root, top_level);
+
+	MemoryContextSwitchTo(old_ctx);
+
+	return iter;
+}
+
+/*
+ * Return true with setting key_p and value_p if there is next key.  Otherwise
+ * return false.
+ */
+RT_SCOPE bool
+RT_ITERATE_NEXT(RT_ITER *iter, uint64 *key_p, RT_VALUE_TYPE *value_p)
+{
+	/* Empty tree */
+	if (!iter->tree->ctl->root)
+		return false;
+
+	for (;;)
+	{
+		RT_PTR_LOCAL child = NULL;
+		RT_VALUE_TYPE value;
+		int			level;
+		bool		found;
+
+		/* Advance the leaf node iterator to get next key-value pair */
+		found = RT_NODE_LEAF_ITERATE_NEXT(iter, &(iter->stack[0]), &value);
+
+		if (found)
+		{
+			*key_p = iter->key;
+			*value_p = value;
+			return true;
+		}
+
+		/*
+		 * We've visited all values in the leaf node, so advance inner node
+		 * iterators from the level=1 until we find the next child node.
+		 */
+		for (level = 1; level <= iter->stack_len; level++)
+		{
+			child = RT_NODE_INNER_ITERATE_NEXT(iter, &(iter->stack[level]));
+
+			if (child)
+				break;
+		}
+
+		/* the iteration finished */
+		if (!child)
+			return false;
+
+		/*
+		 * Set the node to the node iterator and update the iterator stack
+		 * from this node.
+		 */
+		RT_UPDATE_ITER_STACK(iter, child, level - 1);
+
+		/* Node iterators are updated, so try again from the leaf */
+	}
+
+	return false;
+}
+
+/*
+ * Terminate the iteration and release the lock.
+ *
+ * This function needs to be called after finishing or when exiting an
+ * iteration.
+ */
+RT_SCOPE void
+RT_END_ITERATE(RT_ITER *iter)
+{
+#ifdef RT_SHMEM
+	Assert(LWLockHeldByMe(&iter->tree->ctl->lock));
+#endif
+
+	RT_UNLOCK(iter->tree);
+	pfree(iter);
+}
+
+/*
+ * Return the statistics of the amount of memory used by the radix tree.
+ */
+RT_SCOPE uint64
+RT_MEMORY_USAGE(RT_RADIX_TREE *tree)
+{
+	Size		total = 0;
+
+	RT_LOCK_SHARED(tree);
+
+#ifdef RT_SHMEM
+	Assert(tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+	total = dsa_get_total_size(tree->dsa);
+#else
+	for (int i = 0; i < RT_SIZE_CLASS_COUNT; i++)
+	{
+		total += MemoryContextMemAllocated(tree->inner_slabs[i], true);
+		total += MemoryContextMemAllocated(tree->leaf_slabs[i], true);
+	}
+#endif
+
+	RT_UNLOCK(tree);
+	return total;
+}
+
+/*
+ * Verify the radix tree node.
+ */
+static void
+RT_VERIFY_NODE(RT_PTR_LOCAL node)
+{
+#ifdef USE_ASSERT_CHECKING
+	Assert(node->count >= 0);
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE_BASE_3 *n3 = (RT_NODE_BASE_3 *) node;
+
+				for (int i = 1; i < n3->n.count; i++)
+					Assert(n3->chunks[i - 1] < n3->chunks[i]);
+
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				RT_NODE_BASE_32 *n32 = (RT_NODE_BASE_32 *) node;
+
+				for (int i = 1; i < n32->n.count; i++)
+					Assert(n32->chunks[i - 1] < n32->chunks[i]);
+
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE_BASE_125 *n125 = (RT_NODE_BASE_125 *) node;
+				int			cnt = 0;
+
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					uint8		slot = n125->slot_idxs[i];
+					int			idx = RT_BM_IDX(slot);
+					int			bitnum = RT_BM_BIT(slot);
+
+					if (!RT_NODE_125_IS_CHUNK_USED(n125, i))
+						continue;
+
+					/* Check if the corresponding slot is used */
+					Assert(slot < node->fanout);
+					Assert((n125->isset[idx] & ((bitmapword) 1 << bitnum)) != 0);
+
+					cnt++;
+				}
+
+				Assert(n125->n.count == cnt);
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				if (RT_NODE_IS_LEAF(node))
+				{
+					RT_NODE_LEAF_256 *n256 = (RT_NODE_LEAF_256 *) node;
+					int			cnt = 0;
+
+					for (int i = 0; i < RT_BM_IDX(RT_NODE_MAX_SLOTS); i++)
+						cnt += bmw_popcount(n256->isset[i]);
+
+					/* Check if the number of used chunk matches */
+					Assert(n256->base.n.count == cnt);
+
+					break;
+				}
+			}
+	}
+#endif
+}
+
+/***************** DEBUG FUNCTIONS *****************/
+#ifdef RT_DEBUG
+
+#define RT_UINT64_FORMAT_HEX "%" INT64_MODIFIER "X"
+
+RT_SCOPE void
+RT_STATS(RT_RADIX_TREE *tree)
+{
+	RT_LOCK_SHARED(tree);
+
+	fprintf(stderr, "max_val = " UINT64_FORMAT "\n", tree->ctl->max_val);
+	fprintf(stderr, "num_keys = " UINT64_FORMAT "\n", tree->ctl->num_keys);
+
+#ifdef RT_SHMEM
+	fprintf(stderr, "handle = " UINT64_FORMAT "\n", tree->ctl->handle);
+#endif
+
+	if (RT_PTR_ALLOC_IS_VALID(tree->ctl->root))
+	{
+		RT_PTR_LOCAL root = RT_PTR_GET_LOCAL(tree, tree->ctl->root);
+
+		fprintf(stderr, "height = %d, n3 = %u, n15 = %u, n32 = %u, n125 = %u, n256 = %u\n",
+				root->shift / RT_NODE_SPAN,
+				tree->ctl->cnt[RT_CLASS_3],
+				tree->ctl->cnt[RT_CLASS_32_MIN],
+				tree->ctl->cnt[RT_CLASS_32_MAX],
+				tree->ctl->cnt[RT_CLASS_125],
+				tree->ctl->cnt[RT_CLASS_256]);
+	}
+
+	RT_UNLOCK(tree);
+}
+
+static void
+RT_DUMP_NODE(RT_RADIX_TREE *tree, RT_PTR_ALLOC allocnode, int level,
+			 bool recurse, StringInfo buf)
+{
+	RT_PTR_LOCAL node = RT_PTR_GET_LOCAL(tree, allocnode);
+	StringInfoData spaces;
+
+	initStringInfo(&spaces);
+	appendStringInfoSpaces(&spaces, (level * 4) + 1);
+
+	appendStringInfo(buf, "%s%s[%s] kind %d, fanout %d, count %u, shift %u:\n",
+					 spaces.data,
+					 level == 0 ? "" : "-> ",
+					 RT_NODE_IS_LEAF(node) ? "LEAF" : "INNR",
+					 (node->kind == RT_NODE_KIND_3) ? 3 :
+					 (node->kind == RT_NODE_KIND_32) ? 32 :
+					 (node->kind == RT_NODE_KIND_125) ? 125 : 256,
+					 node->fanout == 0 ? 256 : node->fanout,
+					 node->count, node->shift);
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				for (int i = 0; i < node->count; i++)
+				{
+					if (RT_NODE_IS_LEAF(node))
+					{
+						RT_NODE_LEAF_3 *n3 = (RT_NODE_LEAF_3 *) node;
+
+						appendStringInfo(buf, "%schunk[%d] 0x%X\n",
+										 spaces.data, i, n3->base.chunks[i]);
+					}
+					else
+					{
+						RT_NODE_INNER_3 *n3 = (RT_NODE_INNER_3 *) node;
+
+						appendStringInfo(buf, "%schunk[%d] 0x%X",
+										 spaces.data, i, n3->base.chunks[i]);
+
+						if (recurse)
+						{
+							appendStringInfo(buf, "\n");
+							RT_DUMP_NODE(tree, n3->children[i], level + 1,
+										 recurse, buf);
+						}
+						else
+							appendStringInfo(buf, " (skipped)\n");
+					}
+				}
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				for (int i = 0; i < node->count; i++)
+				{
+					if (RT_NODE_IS_LEAF(node))
+					{
+						RT_NODE_LEAF_32 *n32 = (RT_NODE_LEAF_32 *) node;
+
+						appendStringInfo(buf, "%schunk[%d] 0x%X\n",
+										 spaces.data, i, n32->base.chunks[i]);
+					}
+					else
+					{
+						RT_NODE_INNER_32 *n32 = (RT_NODE_INNER_32 *) node;
+
+						appendStringInfo(buf, "%schunk[%d] 0x%X",
+										 spaces.data, i, n32->base.chunks[i]);
+
+						if (recurse)
+						{
+							appendStringInfo(buf, "\n");
+							RT_DUMP_NODE(tree, n32->children[i], level + 1,
+										 recurse, buf);
+						}
+						else
+							appendStringInfo(buf, " (skipped)\n");
+
+					}
+				}
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE_BASE_125 *b125 = (RT_NODE_BASE_125 *) node;
+				char *sep = "";
+
+				appendStringInfo(buf, "%sslot_idxs: ", spaces.data);
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (!RT_NODE_125_IS_CHUNK_USED(b125, i))
+						continue;
+
+					appendStringInfo(buf, "%s[%d]=%d ",
+									 sep, i, b125->slot_idxs[i]);
+					sep = ",";
+				}
+
+				appendStringInfo(buf, "\n%sisset-bitmap: ", spaces.data);
+				for (int i = 0; i < (RT_SLOT_IDX_LIMIT / BITS_PER_BYTE); i++)
+					appendStringInfo(buf, "%X ", ((uint8 *) b125->isset)[i]);
+				appendStringInfo(buf, "\n");
+
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (!RT_NODE_125_IS_CHUNK_USED(b125, i))
+						continue;
+
+					if (RT_NODE_IS_LEAF(node))
+						appendStringInfo(buf, "%schunk 0x%X\n",
+										 spaces.data, i);
+					else
+					{
+						RT_NODE_INNER_125 *n125 = (RT_NODE_INNER_125 *) b125;
+
+						appendStringInfo(buf, "%schunk 0x%X",
+										 spaces.data, i);
+
+						if (recurse)
+						{
+							appendStringInfo(buf, "\n");
+							RT_DUMP_NODE(tree, RT_NODE_INNER_125_GET_CHILD(n125, i),
+										 level + 1, recurse, buf);
+						}
+						else
+							appendStringInfo(buf, " (skipped)\n");
+					}
+				}
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				if (RT_NODE_IS_LEAF(node))
+				{
+					RT_NODE_LEAF_256 *n256 = (RT_NODE_LEAF_256 *) node;
+
+					appendStringInfo(buf, "%sisset-bitmap: ", spaces.data);
+					for (int i = 0; i < (RT_SLOT_IDX_LIMIT / BITS_PER_BYTE); i++)
+						appendStringInfo(buf, "%X ", ((uint8 *) n256->isset)[i]);
+					appendStringInfo(buf, "\n");
+				}
+
+				for (int i = 0; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (RT_NODE_IS_LEAF(node))
+					{
+						RT_NODE_LEAF_256 *n256 = (RT_NODE_LEAF_256 *) node;
+
+						if (!RT_NODE_LEAF_256_IS_CHUNK_USED(n256, i))
+							continue;
+
+						appendStringInfo(buf, "%schunk 0x%X\n",
+										 spaces.data, i);
+					}
+					else
+					{
+						RT_NODE_INNER_256 *n256 = (RT_NODE_INNER_256 *) node;
+
+						if (!RT_NODE_INNER_256_IS_CHUNK_USED(n256, i))
+							continue;
+
+						appendStringInfo(buf, "%schunk 0x%X",
+										 spaces.data, i);
+
+						if (recurse)
+						{
+							appendStringInfo(buf, "\n");
+							RT_DUMP_NODE(tree, RT_NODE_INNER_256_GET_CHILD(n256, i),
+										 level + 1, recurse, buf);
+						}
+						else
+							appendStringInfo(buf, " (skipped)\n");
+					}
+				}
+				break;
+			}
+	}
+}
+
+RT_SCOPE void
+RT_DUMP_SEARCH(RT_RADIX_TREE *tree, uint64 key)
+{
+	RT_PTR_ALLOC allocnode;
+	RT_PTR_LOCAL node;
+	StringInfoData buf;
+	int			shift;
+	int			level = 0;
+
+	RT_STATS(tree);
+
+	RT_LOCK_SHARED(tree);
+
+	if (!RT_PTR_ALLOC_IS_VALID(tree->ctl->root))
+	{
+		RT_UNLOCK(tree);
+		fprintf(stderr, "empty tree\n");
+		return;
+	}
+
+	if (key > tree->ctl->max_val)
+	{
+		RT_UNLOCK(tree);
+		fprintf(stderr, "key " UINT64_FORMAT "(0x" RT_UINT64_FORMAT_HEX ") is larger than max val\n",
+				key, key);
+		return;
+	}
+
+	initStringInfo(&buf);
+	allocnode = tree->ctl->root;
+	node = RT_PTR_GET_LOCAL(tree, allocnode);
+	shift = node->shift;
+	while (shift >= 0)
+	{
+		RT_PTR_ALLOC child;
+
+		RT_DUMP_NODE(tree, allocnode, level, false, &buf);
+
+		if (RT_NODE_IS_LEAF(node))
+		{
+			RT_VALUE_TYPE	dummy;
+
+			/* We reached at a leaf node, find the corresponding slot */
+			RT_NODE_SEARCH_LEAF(node, key, &dummy);
+
+			break;
+		}
+
+		if (!RT_NODE_SEARCH_INNER(node, key, &child))
+			break;
+
+		allocnode = child;
+		node = RT_PTR_GET_LOCAL(tree, allocnode);
+		shift -= RT_NODE_SPAN;
+		level++;
+	}
+	RT_UNLOCK(tree);
+
+	fprintf(stderr, "%s", buf.data);
+}
+
+RT_SCOPE void
+RT_DUMP(RT_RADIX_TREE *tree)
+{
+	StringInfoData buf;
+
+	RT_STATS(tree);
+
+	RT_LOCK_SHARED(tree);
+
+	if (!RT_PTR_ALLOC_IS_VALID(tree->ctl->root))
+	{
+		RT_UNLOCK(tree);
+		fprintf(stderr, "empty tree\n");
+		return;
+	}
+
+	initStringInfo(&buf);
+
+	RT_DUMP_NODE(tree, tree->ctl->root, 0, true, &buf);
+	RT_UNLOCK(tree);
+
+	fprintf(stderr, "%s",buf.data);
+}
+#endif
+
+#endif							/* RT_DEFINE */
+
+
+/* undefine external parameters, so next radix tree can be defined */
+#undef RT_PREFIX
+#undef RT_SCOPE
+#undef RT_DECLARE
+#undef RT_DEFINE
+#undef RT_VALUE_TYPE
+
+/* locally declared macros */
+#undef RT_MAKE_PREFIX
+#undef RT_MAKE_NAME
+#undef RT_MAKE_NAME_
+#undef RT_NODE_SPAN
+#undef RT_NODE_MAX_SLOTS
+#undef RT_CHUNK_MASK
+#undef RT_MAX_SHIFT
+#undef RT_MAX_LEVEL
+#undef RT_GET_KEY_CHUNK
+#undef RT_BM_IDX
+#undef RT_BM_BIT
+#undef RT_LOCK_EXCLUSIVE
+#undef RT_LOCK_SHARED
+#undef RT_UNLOCK
+#undef RT_NODE_IS_LEAF
+#undef RT_NODE_MUST_GROW
+#undef RT_NODE_KIND_COUNT
+#undef RT_SIZE_CLASS_COUNT
+#undef RT_SLOT_IDX_LIMIT
+#undef RT_INVALID_SLOT_IDX
+#undef RT_SLAB_BLOCK_SIZE
+#undef RT_RADIX_TREE_MAGIC
+#undef RT_UINT64_FORMAT_HEX
+
+/* type declarations */
+#undef RT_RADIX_TREE
+#undef RT_RADIX_TREE_CONTROL
+#undef RT_PTR_LOCAL
+#undef RT_PTR_ALLOC
+#undef RT_INVALID_PTR_ALLOC
+#undef RT_HANDLE
+#undef RT_ITER
+#undef RT_NODE
+#undef RT_NODE_ITER
+#undef RT_NODE_KIND_3
+#undef RT_NODE_KIND_32
+#undef RT_NODE_KIND_125
+#undef RT_NODE_KIND_256
+#undef RT_NODE_BASE_3
+#undef RT_NODE_BASE_32
+#undef RT_NODE_BASE_125
+#undef RT_NODE_BASE_256
+#undef RT_NODE_INNER_3
+#undef RT_NODE_INNER_32
+#undef RT_NODE_INNER_125
+#undef RT_NODE_INNER_256
+#undef RT_NODE_LEAF_3
+#undef RT_NODE_LEAF_32
+#undef RT_NODE_LEAF_125
+#undef RT_NODE_LEAF_256
+#undef RT_SIZE_CLASS
+#undef RT_SIZE_CLASS_ELEM
+#undef RT_SIZE_CLASS_INFO
+#undef RT_CLASS_3
+#undef RT_CLASS_32_MIN
+#undef RT_CLASS_32_MAX
+#undef RT_CLASS_125
+#undef RT_CLASS_256
+
+/* function declarations */
+#undef RT_CREATE
+#undef RT_FREE
+#undef RT_ATTACH
+#undef RT_DETACH
+#undef RT_GET_HANDLE
+#undef RT_SEARCH
+#undef RT_SET
+#undef RT_BEGIN_ITERATE
+#undef RT_ITERATE_NEXT
+#undef RT_END_ITERATE
+#undef RT_USE_DELETE
+#undef RT_DELETE
+#undef RT_MEMORY_USAGE
+#undef RT_DUMP
+#undef RT_DUMP_NODE
+#undef RT_DUMP_SEARCH
+#undef RT_STATS
+
+/* internal helper functions */
+#undef RT_NEW_ROOT
+#undef RT_ALLOC_NODE
+#undef RT_INIT_NODE
+#undef RT_FREE_NODE
+#undef RT_FREE_RECURSE
+#undef RT_EXTEND
+#undef RT_SET_EXTEND
+#undef RT_SWITCH_NODE_KIND
+#undef RT_COPY_NODE
+#undef RT_REPLACE_NODE
+#undef RT_PTR_GET_LOCAL
+#undef RT_PTR_ALLOC_IS_VALID
+#undef RT_NODE_3_SEARCH_EQ
+#undef RT_NODE_32_SEARCH_EQ
+#undef RT_NODE_3_GET_INSERTPOS
+#undef RT_NODE_32_GET_INSERTPOS
+#undef RT_CHUNK_CHILDREN_ARRAY_SHIFT
+#undef RT_CHUNK_VALUES_ARRAY_SHIFT
+#undef RT_CHUNK_CHILDREN_ARRAY_DELETE
+#undef RT_CHUNK_VALUES_ARRAY_DELETE
+#undef RT_CHUNK_CHILDREN_ARRAY_COPY
+#undef RT_CHUNK_VALUES_ARRAY_COPY
+#undef RT_NODE_125_IS_CHUNK_USED
+#undef RT_NODE_INNER_125_GET_CHILD
+#undef RT_NODE_LEAF_125_GET_VALUE
+#undef RT_NODE_INNER_256_IS_CHUNK_USED
+#undef RT_NODE_LEAF_256_IS_CHUNK_USED
+#undef RT_NODE_INNER_256_GET_CHILD
+#undef RT_NODE_LEAF_256_GET_VALUE
+#undef RT_NODE_INNER_256_SET
+#undef RT_NODE_LEAF_256_SET
+#undef RT_NODE_INNER_256_DELETE
+#undef RT_NODE_LEAF_256_DELETE
+#undef RT_KEY_GET_SHIFT
+#undef RT_SHIFT_GET_MAX_VAL
+#undef RT_NODE_SEARCH_INNER
+#undef RT_NODE_SEARCH_LEAF
+#undef RT_NODE_UPDATE_INNER
+#undef RT_NODE_DELETE_INNER
+#undef RT_NODE_DELETE_LEAF
+#undef RT_NODE_INSERT_INNER
+#undef RT_NODE_INSERT_LEAF
+#undef RT_NODE_INNER_ITERATE_NEXT
+#undef RT_NODE_LEAF_ITERATE_NEXT
+#undef RT_UPDATE_ITER_STACK
+#undef RT_ITER_UPDATE_KEY
+#undef RT_VERIFY_NODE
+
+#undef RT_DEBUG
diff --git a/src/include/lib/radixtree_delete_impl.h b/src/include/lib/radixtree_delete_impl.h
new file mode 100644
index 0000000000..5f6dda1f12
--- /dev/null
+++ b/src/include/lib/radixtree_delete_impl.h
@@ -0,0 +1,122 @@
+/*-------------------------------------------------------------------------
+ *
+ * radixtree_delete_impl.h
+ *	  Common implementation for deletion in leaf and inner nodes.
+ *
+ * Note: There is deliberately no #include guard here
+ *
+ * TODO: Shrink nodes when deletion would allow them to fit in a smaller
+ * size class.
+ *
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * src/include/lib/radixtree_delete_impl.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#if defined(RT_NODE_LEVEL_INNER)
+#define RT_NODE3_TYPE RT_NODE_INNER_3
+#define RT_NODE32_TYPE RT_NODE_INNER_32
+#define RT_NODE125_TYPE RT_NODE_INNER_125
+#define RT_NODE256_TYPE RT_NODE_INNER_256
+#elif defined(RT_NODE_LEVEL_LEAF)
+#define RT_NODE3_TYPE RT_NODE_LEAF_3
+#define RT_NODE32_TYPE RT_NODE_LEAF_32
+#define RT_NODE125_TYPE RT_NODE_LEAF_125
+#define RT_NODE256_TYPE RT_NODE_LEAF_256
+#else
+#error node level must be either inner or leaf
+#endif
+
+	uint8		chunk = RT_GET_KEY_CHUNK(key, node->shift);
+
+#ifdef RT_NODE_LEVEL_LEAF
+	Assert(RT_NODE_IS_LEAF(node));
+#else
+	Assert(!RT_NODE_IS_LEAF(node));
+#endif
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE3_TYPE *n3 = (RT_NODE3_TYPE *) node;
+				int			idx = RT_NODE_3_SEARCH_EQ((RT_NODE_BASE_3 *) n3, chunk);
+
+				if (idx < 0)
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				RT_CHUNK_VALUES_ARRAY_DELETE(n3->base.chunks, n3->values,
+										  n3->base.n.count, idx);
+#else
+				RT_CHUNK_CHILDREN_ARRAY_DELETE(n3->base.chunks, n3->children,
+											n3->base.n.count, idx);
+#endif
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				RT_NODE32_TYPE *n32 = (RT_NODE32_TYPE *) node;
+				int			idx = RT_NODE_32_SEARCH_EQ((RT_NODE_BASE_32 *) n32, chunk);
+
+				if (idx < 0)
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				RT_CHUNK_VALUES_ARRAY_DELETE(n32->base.chunks, n32->values,
+										  n32->base.n.count, idx);
+#else
+				RT_CHUNK_CHILDREN_ARRAY_DELETE(n32->base.chunks, n32->children,
+											n32->base.n.count, idx);
+#endif
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE125_TYPE *n125 = (RT_NODE125_TYPE *) node;
+				int			slotpos = n125->base.slot_idxs[chunk];
+				int			idx;
+				int			bitnum;
+
+				if (slotpos == RT_INVALID_SLOT_IDX)
+					return false;
+
+				idx = RT_BM_IDX(slotpos);
+				bitnum = RT_BM_BIT(slotpos);
+				n125->base.isset[idx] &= ~((bitmapword) 1 << bitnum);
+				n125->base.slot_idxs[chunk] = RT_INVALID_SLOT_IDX;
+
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				RT_NODE256_TYPE *n256 = (RT_NODE256_TYPE *) node;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				if (!RT_NODE_LEAF_256_IS_CHUNK_USED(n256, chunk))
+#else
+				if (!RT_NODE_INNER_256_IS_CHUNK_USED(n256, chunk))
+#endif
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				RT_NODE_LEAF_256_DELETE(n256, chunk);
+#else
+				RT_NODE_INNER_256_DELETE(n256, chunk);
+#endif
+				break;
+			}
+	}
+
+	/* update statistics */
+	node->count--;
+
+	return true;
+
+#undef RT_NODE3_TYPE
+#undef RT_NODE32_TYPE
+#undef RT_NODE125_TYPE
+#undef RT_NODE256_TYPE
diff --git a/src/include/lib/radixtree_insert_impl.h b/src/include/lib/radixtree_insert_impl.h
new file mode 100644
index 0000000000..d56e58dcac
--- /dev/null
+++ b/src/include/lib/radixtree_insert_impl.h
@@ -0,0 +1,328 @@
+/*-------------------------------------------------------------------------
+ *
+ * radixtree_insert_impl.h
+ *	  Common implementation for insertion in leaf and inner nodes.
+ *
+ * Note: There is deliberately no #include guard here
+ *
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * src/include/lib/radixtree_insert_impl.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#if defined(RT_NODE_LEVEL_INNER)
+#define RT_NODE3_TYPE RT_NODE_INNER_3
+#define RT_NODE32_TYPE RT_NODE_INNER_32
+#define RT_NODE125_TYPE RT_NODE_INNER_125
+#define RT_NODE256_TYPE RT_NODE_INNER_256
+#elif defined(RT_NODE_LEVEL_LEAF)
+#define RT_NODE3_TYPE RT_NODE_LEAF_3
+#define RT_NODE32_TYPE RT_NODE_LEAF_32
+#define RT_NODE125_TYPE RT_NODE_LEAF_125
+#define RT_NODE256_TYPE RT_NODE_LEAF_256
+#else
+#error node level must be either inner or leaf
+#endif
+
+	uint8		chunk = RT_GET_KEY_CHUNK(key, node->shift);
+
+#ifdef RT_NODE_LEVEL_LEAF
+	const bool is_leaf = true;
+	bool		chunk_exists = false;
+	Assert(RT_NODE_IS_LEAF(node));
+#else
+	const bool is_leaf = false;
+	Assert(!RT_NODE_IS_LEAF(node));
+#endif
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE3_TYPE *n3 = (RT_NODE3_TYPE *) node;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				int idx = RT_NODE_3_SEARCH_EQ(&n3->base, chunk);
+
+				if (idx != -1)
+				{
+					/* found the existing chunk */
+					chunk_exists = true;
+					n3->values[idx] = *value_p;
+					break;
+				}
+#endif
+				if (unlikely(RT_NODE_MUST_GROW(n3)))
+				{
+					RT_PTR_ALLOC allocnode;
+					RT_PTR_LOCAL newnode;
+					RT_NODE32_TYPE *new32;
+					const uint8 new_kind = RT_NODE_KIND_32;
+					const RT_SIZE_CLASS new_class = RT_CLASS_32_MIN;
+
+					/* grow node from 3 to 32 */
+					allocnode = RT_ALLOC_NODE(tree, new_class, is_leaf);
+					newnode = RT_SWITCH_NODE_KIND(tree, allocnode, node, new_kind, new_class, is_leaf);
+					new32 = (RT_NODE32_TYPE *) newnode;
+
+#ifdef RT_NODE_LEVEL_LEAF
+					RT_CHUNK_VALUES_ARRAY_COPY(n3->base.chunks, n3->values,
+											  new32->base.chunks, new32->values);
+#else
+					RT_CHUNK_CHILDREN_ARRAY_COPY(n3->base.chunks, n3->children,
+											  new32->base.chunks, new32->children);
+#endif
+					RT_REPLACE_NODE(tree, parent, stored_node, node, allocnode, key);
+					node = newnode;
+				}
+				else
+				{
+					int			insertpos = RT_NODE_3_GET_INSERTPOS(&n3->base, chunk);
+					int			count = n3->base.n.count;
+
+					/* shift chunks and children */
+					if (insertpos < count)
+					{
+						Assert(count > 0);
+#ifdef RT_NODE_LEVEL_LEAF
+						RT_CHUNK_VALUES_ARRAY_SHIFT(n3->base.chunks, n3->values,
+												   count, insertpos);
+#else
+						RT_CHUNK_CHILDREN_ARRAY_SHIFT(n3->base.chunks, n3->children,
+												   count, insertpos);
+#endif
+					}
+
+					n3->base.chunks[insertpos] = chunk;
+#ifdef RT_NODE_LEVEL_LEAF
+					n3->values[insertpos] = *value_p;
+#else
+					n3->children[insertpos] = child;
+#endif
+					break;
+				}
+			}
+			/* FALLTHROUGH */
+		case RT_NODE_KIND_32:
+			{
+				const RT_SIZE_CLASS_ELEM class32_max = RT_SIZE_CLASS_INFO[RT_CLASS_32_MAX];
+				RT_NODE32_TYPE *n32 = (RT_NODE32_TYPE *) node;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				int idx = RT_NODE_32_SEARCH_EQ(&n32->base, chunk);
+
+				if (idx != -1)
+				{
+					/* found the existing chunk */
+					chunk_exists = true;
+					n32->values[idx] = *value_p;
+					break;
+				}
+#endif
+				if (unlikely(RT_NODE_MUST_GROW(n32)) &&
+					n32->base.n.fanout < class32_max.fanout)
+				{
+					RT_PTR_ALLOC allocnode;
+					RT_PTR_LOCAL newnode;
+					const RT_SIZE_CLASS_ELEM class32_min = RT_SIZE_CLASS_INFO[RT_CLASS_32_MIN];
+					const RT_SIZE_CLASS new_class = RT_CLASS_32_MAX;
+
+					Assert(n32->base.n.fanout == class32_min.fanout);
+
+					/* grow to the next size class of this kind */
+					allocnode = RT_ALLOC_NODE(tree, new_class, is_leaf);
+					newnode = RT_PTR_GET_LOCAL(tree, allocnode);
+					n32 = (RT_NODE32_TYPE *) newnode;
+
+#ifdef RT_NODE_LEVEL_LEAF
+					memcpy(newnode, node, class32_min.leaf_size);
+#else
+					memcpy(newnode, node, class32_min.inner_size);
+#endif
+					newnode->fanout = class32_max.fanout;
+
+					RT_REPLACE_NODE(tree, parent, stored_node, node, allocnode, key);
+					node = newnode;
+				}
+
+				if (unlikely(RT_NODE_MUST_GROW(n32)))
+				{
+					RT_PTR_ALLOC allocnode;
+					RT_PTR_LOCAL newnode;
+					RT_NODE125_TYPE *new125;
+					const uint8 new_kind = RT_NODE_KIND_125;
+					const RT_SIZE_CLASS new_class = RT_CLASS_125;
+
+					Assert(n32->base.n.fanout == class32_max.fanout);
+
+					/* grow node from 32 to 125 */
+					allocnode = RT_ALLOC_NODE(tree, new_class, is_leaf);
+					newnode = RT_SWITCH_NODE_KIND(tree, allocnode, node, new_kind, new_class, is_leaf);
+					new125 = (RT_NODE125_TYPE *) newnode;
+
+					for (int i = 0; i < class32_max.fanout; i++)
+					{
+						new125->base.slot_idxs[n32->base.chunks[i]] = i;
+#ifdef RT_NODE_LEVEL_LEAF
+						new125->values[i] = n32->values[i];
+#else
+						new125->children[i] = n32->children[i];
+#endif
+					}
+
+					/*
+					 * Since we just copied a dense array, we can set the bits
+					 * using a single store, provided the length of that array
+					 * is at most the number of bits in a bitmapword.
+					 */
+					Assert(class32_max.fanout <= sizeof(bitmapword) * BITS_PER_BYTE);
+					new125->base.isset[0] = (bitmapword) (((uint64) 1 << class32_max.fanout) - 1);
+
+					RT_REPLACE_NODE(tree, parent, stored_node, node, allocnode, key);
+					node = newnode;
+				}
+				else
+				{
+					int	insertpos = RT_NODE_32_GET_INSERTPOS(&n32->base, chunk);
+					int count = n32->base.n.count;
+
+					if (insertpos < count)
+					{
+						Assert(count > 0);
+#ifdef RT_NODE_LEVEL_LEAF
+						RT_CHUNK_VALUES_ARRAY_SHIFT(n32->base.chunks, n32->values,
+												   count, insertpos);
+#else
+						RT_CHUNK_CHILDREN_ARRAY_SHIFT(n32->base.chunks, n32->children,
+												   count, insertpos);
+#endif
+					}
+
+					n32->base.chunks[insertpos] = chunk;
+#ifdef RT_NODE_LEVEL_LEAF
+					n32->values[insertpos] = *value_p;
+#else
+					n32->children[insertpos] = child;
+#endif
+					break;
+				}
+			}
+			/* FALLTHROUGH */
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE125_TYPE *n125 = (RT_NODE125_TYPE *) node;
+				int			slotpos;
+				int			cnt = 0;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				slotpos = n125->base.slot_idxs[chunk];
+				if (slotpos != RT_INVALID_SLOT_IDX)
+				{
+					/* found the existing chunk */
+					chunk_exists = true;
+					n125->values[slotpos] = *value_p;
+					break;
+				}
+#endif
+				if (unlikely(RT_NODE_MUST_GROW(n125)))
+				{
+					RT_PTR_ALLOC allocnode;
+					RT_PTR_LOCAL newnode;
+					RT_NODE256_TYPE *new256;
+					const uint8 new_kind = RT_NODE_KIND_256;
+					const RT_SIZE_CLASS new_class = RT_CLASS_256;
+
+					/* grow node from 125 to 256 */
+					allocnode = RT_ALLOC_NODE(tree, new_class, is_leaf);
+					newnode = RT_SWITCH_NODE_KIND(tree, allocnode, node, new_kind, new_class, is_leaf);
+					new256 = (RT_NODE256_TYPE *) newnode;
+
+					for (int i = 0; i < RT_NODE_MAX_SLOTS && cnt < n125->base.n.count; i++)
+					{
+						if (!RT_NODE_125_IS_CHUNK_USED(&n125->base, i))
+							continue;
+#ifdef RT_NODE_LEVEL_LEAF
+						RT_NODE_LEAF_256_SET(new256, i, RT_NODE_LEAF_125_GET_VALUE(n125, i));
+#else
+						RT_NODE_INNER_256_SET(new256, i, RT_NODE_INNER_125_GET_CHILD(n125, i));
+#endif
+						cnt++;
+					}
+
+					RT_REPLACE_NODE(tree, parent, stored_node, node, allocnode, key);
+					node = newnode;
+				}
+				else
+				{
+					int			idx;
+					bitmapword	inverse;
+
+					/* get the first word with at least one bit not set */
+					for (idx = 0; idx < RT_BM_IDX(RT_SLOT_IDX_LIMIT); idx++)
+					{
+						if (n125->base.isset[idx] < ~((bitmapword) 0))
+							break;
+					}
+
+					/* To get the first unset bit in X, get the first set bit in ~X */
+					inverse = ~(n125->base.isset[idx]);
+					slotpos = idx * BITS_PER_BITMAPWORD;
+					slotpos += bmw_rightmost_one_pos(inverse);
+					Assert(slotpos < node->fanout);
+
+					/* mark the slot used */
+					n125->base.isset[idx] |= bmw_rightmost_one(inverse);
+					n125->base.slot_idxs[chunk] = slotpos;
+
+#ifdef RT_NODE_LEVEL_LEAF
+					n125->values[slotpos] = *value_p;
+#else
+					n125->children[slotpos] = child;
+#endif
+					break;
+				}
+			}
+			/* FALLTHROUGH */
+		case RT_NODE_KIND_256:
+			{
+				RT_NODE256_TYPE *n256 = (RT_NODE256_TYPE *) node;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				chunk_exists = RT_NODE_LEAF_256_IS_CHUNK_USED(n256, chunk);
+				Assert(chunk_exists || node->count < RT_NODE_MAX_SLOTS);
+				RT_NODE_LEAF_256_SET(n256, chunk, *value_p);
+#else
+				Assert(node->count < RT_NODE_MAX_SLOTS);
+				RT_NODE_INNER_256_SET(n256, chunk, child);
+#endif
+				break;
+			}
+	}
+
+	/* Update statistics */
+#ifdef RT_NODE_LEVEL_LEAF
+	if (!chunk_exists)
+		node->count++;
+#else
+		node->count++;
+#endif
+
+	/*
+	 * Done. Finally, verify the chunk and value is inserted or replaced
+	 * properly in the node.
+	 */
+	RT_VERIFY_NODE(node);
+
+#ifdef RT_NODE_LEVEL_LEAF
+	return chunk_exists;
+#else
+	return;
+#endif
+
+#undef RT_NODE3_TYPE
+#undef RT_NODE32_TYPE
+#undef RT_NODE125_TYPE
+#undef RT_NODE256_TYPE
diff --git a/src/include/lib/radixtree_iter_impl.h b/src/include/lib/radixtree_iter_impl.h
new file mode 100644
index 0000000000..98c78eb237
--- /dev/null
+++ b/src/include/lib/radixtree_iter_impl.h
@@ -0,0 +1,153 @@
+/*-------------------------------------------------------------------------
+ *
+ * radixtree_iter_impl.h
+ *	  Common implementation for iteration in leaf and inner nodes.
+ *
+ * Note: There is deliberately no #include guard here
+ *
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * src/include/lib/radixtree_iter_impl.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#if defined(RT_NODE_LEVEL_INNER)
+#define RT_NODE3_TYPE RT_NODE_INNER_3
+#define RT_NODE32_TYPE RT_NODE_INNER_32
+#define RT_NODE125_TYPE RT_NODE_INNER_125
+#define RT_NODE256_TYPE RT_NODE_INNER_256
+#elif defined(RT_NODE_LEVEL_LEAF)
+#define RT_NODE3_TYPE RT_NODE_LEAF_3
+#define RT_NODE32_TYPE RT_NODE_LEAF_32
+#define RT_NODE125_TYPE RT_NODE_LEAF_125
+#define RT_NODE256_TYPE RT_NODE_LEAF_256
+#else
+#error node level must be either inner or leaf
+#endif
+
+	bool		found = false;
+	uint8		key_chunk;
+
+#ifdef RT_NODE_LEVEL_LEAF
+	RT_VALUE_TYPE		value;
+
+	Assert(RT_NODE_IS_LEAF(node_iter->node));
+#else
+	RT_PTR_LOCAL child = NULL;
+
+	Assert(!RT_NODE_IS_LEAF(node_iter->node));
+#endif
+
+#ifdef RT_SHMEM
+	Assert(iter->tree->ctl->magic == RT_RADIX_TREE_MAGIC);
+#endif
+
+	switch (node_iter->node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE3_TYPE *n3 = (RT_NODE3_TYPE *) node_iter->node;
+
+				node_iter->current_idx++;
+				if (node_iter->current_idx >= n3->base.n.count)
+					break;
+#ifdef RT_NODE_LEVEL_LEAF
+				value = n3->values[node_iter->current_idx];
+#else
+				child = RT_PTR_GET_LOCAL(iter->tree, n3->children[node_iter->current_idx]);
+#endif
+				key_chunk = n3->base.chunks[node_iter->current_idx];
+				found = true;
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				RT_NODE32_TYPE *n32 = (RT_NODE32_TYPE *) node_iter->node;
+
+				node_iter->current_idx++;
+				if (node_iter->current_idx >= n32->base.n.count)
+					break;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				value = n32->values[node_iter->current_idx];
+#else
+				child = RT_PTR_GET_LOCAL(iter->tree, n32->children[node_iter->current_idx]);
+#endif
+				key_chunk = n32->base.chunks[node_iter->current_idx];
+				found = true;
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE125_TYPE *n125 = (RT_NODE125_TYPE *) node_iter->node;
+				int			i;
+
+				for (i = node_iter->current_idx + 1; i < RT_NODE_MAX_SLOTS; i++)
+				{
+					if (RT_NODE_125_IS_CHUNK_USED((RT_NODE_BASE_125 *) n125, i))
+						break;
+				}
+
+				if (i >= RT_NODE_MAX_SLOTS)
+					break;
+
+				node_iter->current_idx = i;
+#ifdef RT_NODE_LEVEL_LEAF
+				value = RT_NODE_LEAF_125_GET_VALUE(n125, i);
+#else
+				child = RT_PTR_GET_LOCAL(iter->tree, RT_NODE_INNER_125_GET_CHILD(n125, i));
+#endif
+				key_chunk = i;
+				found = true;
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				RT_NODE256_TYPE *n256 = (RT_NODE256_TYPE *) node_iter->node;
+				int			i;
+
+				for (i = node_iter->current_idx + 1; i < RT_NODE_MAX_SLOTS; i++)
+				{
+#ifdef RT_NODE_LEVEL_LEAF
+					if (RT_NODE_LEAF_256_IS_CHUNK_USED(n256, i))
+#else
+					if (RT_NODE_INNER_256_IS_CHUNK_USED(n256, i))
+#endif
+						break;
+				}
+
+				if (i >= RT_NODE_MAX_SLOTS)
+					break;
+
+				node_iter->current_idx = i;
+#ifdef RT_NODE_LEVEL_LEAF
+				value = RT_NODE_LEAF_256_GET_VALUE(n256, i);
+#else
+				child = RT_PTR_GET_LOCAL(iter->tree, RT_NODE_INNER_256_GET_CHILD(n256, i));
+#endif
+				key_chunk = i;
+				found = true;
+				break;
+			}
+	}
+
+	if (found)
+	{
+		RT_ITER_UPDATE_KEY(iter, key_chunk, node_iter->node->shift);
+#ifdef RT_NODE_LEVEL_LEAF
+		*value_p = value;
+#endif
+	}
+
+#ifdef RT_NODE_LEVEL_LEAF
+	return found;
+#else
+	return child;
+#endif
+
+#undef RT_NODE3_TYPE
+#undef RT_NODE32_TYPE
+#undef RT_NODE125_TYPE
+#undef RT_NODE256_TYPE
diff --git a/src/include/lib/radixtree_search_impl.h b/src/include/lib/radixtree_search_impl.h
new file mode 100644
index 0000000000..a8925c75d0
--- /dev/null
+++ b/src/include/lib/radixtree_search_impl.h
@@ -0,0 +1,138 @@
+/*-------------------------------------------------------------------------
+ *
+ * radixtree_search_impl.h
+ *	  Common implementation for search in leaf and inner nodes, plus
+ *	  update for inner nodes only.
+ *
+ * Note: There is deliberately no #include guard here
+ *
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * src/include/lib/radixtree_search_impl.h
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#if defined(RT_NODE_LEVEL_INNER)
+#define RT_NODE3_TYPE RT_NODE_INNER_3
+#define RT_NODE32_TYPE RT_NODE_INNER_32
+#define RT_NODE125_TYPE RT_NODE_INNER_125
+#define RT_NODE256_TYPE RT_NODE_INNER_256
+#elif defined(RT_NODE_LEVEL_LEAF)
+#define RT_NODE3_TYPE RT_NODE_LEAF_3
+#define RT_NODE32_TYPE RT_NODE_LEAF_32
+#define RT_NODE125_TYPE RT_NODE_LEAF_125
+#define RT_NODE256_TYPE RT_NODE_LEAF_256
+#else
+#error node level must be either inner or leaf
+#endif
+
+	uint8		chunk = RT_GET_KEY_CHUNK(key, node->shift);
+
+#ifdef RT_NODE_LEVEL_LEAF
+	Assert(value_p != NULL);
+	Assert(RT_NODE_IS_LEAF(node));
+#else
+#ifndef RT_ACTION_UPDATE
+	Assert(child_p != NULL);
+#endif
+	Assert(!RT_NODE_IS_LEAF(node));
+#endif
+
+	switch (node->kind)
+	{
+		case RT_NODE_KIND_3:
+			{
+				RT_NODE3_TYPE *n3 = (RT_NODE3_TYPE *) node;
+				int			idx = RT_NODE_3_SEARCH_EQ((RT_NODE_BASE_3 *) n3, chunk);
+
+#ifdef RT_ACTION_UPDATE
+				Assert(idx >= 0);
+				n3->children[idx] = new_child;
+#else
+				if (idx < 0)
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				*value_p = n3->values[idx];
+#else
+				*child_p = n3->children[idx];
+#endif
+#endif							/* RT_ACTION_UPDATE */
+				break;
+			}
+		case RT_NODE_KIND_32:
+			{
+				RT_NODE32_TYPE *n32 = (RT_NODE32_TYPE *) node;
+				int			idx = RT_NODE_32_SEARCH_EQ((RT_NODE_BASE_32 *) n32, chunk);
+
+#ifdef RT_ACTION_UPDATE
+				Assert(idx >= 0);
+				n32->children[idx] = new_child;
+#else
+				if (idx < 0)
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				*value_p = n32->values[idx];
+#else
+				*child_p = n32->children[idx];
+#endif
+#endif							/* RT_ACTION_UPDATE */
+				break;
+			}
+		case RT_NODE_KIND_125:
+			{
+				RT_NODE125_TYPE *n125 = (RT_NODE125_TYPE *) node;
+				int			slotpos = n125->base.slot_idxs[chunk];
+
+#ifdef RT_ACTION_UPDATE
+				Assert(slotpos != RT_INVALID_SLOT_IDX);
+				n125->children[slotpos] = new_child;
+#else
+				if (slotpos == RT_INVALID_SLOT_IDX)
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				*value_p = RT_NODE_LEAF_125_GET_VALUE(n125, chunk);
+#else
+				*child_p = RT_NODE_INNER_125_GET_CHILD(n125, chunk);
+#endif
+#endif							/* RT_ACTION_UPDATE */
+				break;
+			}
+		case RT_NODE_KIND_256:
+			{
+				RT_NODE256_TYPE *n256 = (RT_NODE256_TYPE *) node;
+
+#ifdef RT_ACTION_UPDATE
+				RT_NODE_INNER_256_SET(n256, chunk, new_child);
+#else
+#ifdef RT_NODE_LEVEL_LEAF
+				if (!RT_NODE_LEAF_256_IS_CHUNK_USED(n256, chunk))
+#else
+				if (!RT_NODE_INNER_256_IS_CHUNK_USED(n256, chunk))
+#endif
+					return false;
+
+#ifdef RT_NODE_LEVEL_LEAF
+				*value_p = RT_NODE_LEAF_256_GET_VALUE(n256, chunk);
+#else
+				*child_p = RT_NODE_INNER_256_GET_CHILD(n256, chunk);
+#endif
+#endif							/* RT_ACTION_UPDATE */
+				break;
+			}
+	}
+
+#ifdef RT_ACTION_UPDATE
+	return;
+#else
+	return true;
+#endif							/* RT_ACTION_UPDATE */
+
+#undef RT_NODE3_TYPE
+#undef RT_NODE32_TYPE
+#undef RT_NODE125_TYPE
+#undef RT_NODE256_TYPE
diff --git a/src/include/utils/dsa.h b/src/include/utils/dsa.h
index 3ce4ee300a..2af215484f 100644
--- a/src/include/utils/dsa.h
+++ b/src/include/utils/dsa.h
@@ -121,6 +121,7 @@ extern dsa_handle dsa_get_handle(dsa_area *area);
 extern dsa_pointer dsa_allocate_extended(dsa_area *area, size_t size, int flags);
 extern void dsa_free(dsa_area *area, dsa_pointer dp);
 extern void *dsa_get_address(dsa_area *area, dsa_pointer dp);
+extern size_t dsa_get_total_size(dsa_area *area);
 extern void dsa_trim(dsa_area *area);
 extern void dsa_dump(dsa_area *area);
 
diff --git a/src/test/modules/Makefile b/src/test/modules/Makefile
index c629cbe383..9659eb85d7 100644
--- a/src/test/modules/Makefile
+++ b/src/test/modules/Makefile
@@ -28,6 +28,7 @@ SUBDIRS = \
 		  test_pg_db_role_setting \
 		  test_pg_dump \
 		  test_predtest \
+		  test_radixtree \
 		  test_rbtree \
 		  test_regex \
 		  test_rls_hooks \
diff --git a/src/test/modules/meson.build b/src/test/modules/meson.build
index 1baa6b558d..232cbdac80 100644
--- a/src/test/modules/meson.build
+++ b/src/test/modules/meson.build
@@ -24,6 +24,7 @@ subdir('test_parser')
 subdir('test_pg_db_role_setting')
 subdir('test_pg_dump')
 subdir('test_predtest')
+subdir('test_radixtree')
 subdir('test_rbtree')
 subdir('test_regex')
 subdir('test_rls_hooks')
diff --git a/src/test/modules/test_radixtree/.gitignore b/src/test/modules/test_radixtree/.gitignore
new file mode 100644
index 0000000000..5dcb3ff972
--- /dev/null
+++ b/src/test/modules/test_radixtree/.gitignore
@@ -0,0 +1,4 @@
+# Generated subdirectories
+/log/
+/results/
+/tmp_check/
diff --git a/src/test/modules/test_radixtree/Makefile b/src/test/modules/test_radixtree/Makefile
new file mode 100644
index 0000000000..da06b93da3
--- /dev/null
+++ b/src/test/modules/test_radixtree/Makefile
@@ -0,0 +1,23 @@
+# src/test/modules/test_radixtree/Makefile
+
+MODULE_big = test_radixtree
+OBJS = \
+	$(WIN32RES) \
+	test_radixtree.o
+PGFILEDESC = "test_radixtree - test code for src/backend/lib/radixtree.c"
+
+EXTENSION = test_radixtree
+DATA = test_radixtree--1.0.sql
+
+REGRESS = test_radixtree
+
+ifdef USE_PGXS
+PG_CONFIG = pg_config
+PGXS := $(shell $(PG_CONFIG) --pgxs)
+include $(PGXS)
+else
+subdir = src/test/modules/test_radixtree
+top_builddir = ../../../..
+include $(top_builddir)/src/Makefile.global
+include $(top_srcdir)/contrib/contrib-global.mk
+endif
diff --git a/src/test/modules/test_radixtree/README b/src/test/modules/test_radixtree/README
new file mode 100644
index 0000000000..a8b271869a
--- /dev/null
+++ b/src/test/modules/test_radixtree/README
@@ -0,0 +1,7 @@
+test_integerset contains unit tests for testing the integer set implementation
+in src/backend/lib/integerset.c.
+
+The tests verify the correctness of the implementation, but they can also be
+used as a micro-benchmark.  If you set the 'intset_test_stats' flag in
+test_integerset.c, the tests will print extra information about execution time
+and memory usage.
diff --git a/src/test/modules/test_radixtree/expected/test_radixtree.out b/src/test/modules/test_radixtree/expected/test_radixtree.out
new file mode 100644
index 0000000000..ce645cb8b5
--- /dev/null
+++ b/src/test/modules/test_radixtree/expected/test_radixtree.out
@@ -0,0 +1,36 @@
+CREATE EXTENSION test_radixtree;
+--
+-- All the logic is in the test_radixtree() function. It will throw
+-- an error if something fails.
+--
+SELECT test_radixtree();
+NOTICE:  testing basic operations with leaf node 4
+NOTICE:  testing basic operations with inner node 4
+NOTICE:  testing basic operations with leaf node 32
+NOTICE:  testing basic operations with inner node 32
+NOTICE:  testing basic operations with leaf node 125
+NOTICE:  testing basic operations with inner node 125
+NOTICE:  testing basic operations with leaf node 256
+NOTICE:  testing basic operations with inner node 256
+NOTICE:  testing radix tree node types with shift "0"
+NOTICE:  testing radix tree node types with shift "8"
+NOTICE:  testing radix tree node types with shift "16"
+NOTICE:  testing radix tree node types with shift "24"
+NOTICE:  testing radix tree node types with shift "32"
+NOTICE:  testing radix tree node types with shift "40"
+NOTICE:  testing radix tree node types with shift "48"
+NOTICE:  testing radix tree node types with shift "56"
+NOTICE:  testing radix tree with pattern "all ones"
+NOTICE:  testing radix tree with pattern "alternating bits"
+NOTICE:  testing radix tree with pattern "clusters of ten"
+NOTICE:  testing radix tree with pattern "clusters of hundred"
+NOTICE:  testing radix tree with pattern "one-every-64k"
+NOTICE:  testing radix tree with pattern "sparse"
+NOTICE:  testing radix tree with pattern "single values, distance > 2^32"
+NOTICE:  testing radix tree with pattern "clusters, distance > 2^32"
+NOTICE:  testing radix tree with pattern "clusters, distance > 2^60"
+ test_radixtree 
+----------------
+ 
+(1 row)
+
diff --git a/src/test/modules/test_radixtree/meson.build b/src/test/modules/test_radixtree/meson.build
new file mode 100644
index 0000000000..6add06bbdb
--- /dev/null
+++ b/src/test/modules/test_radixtree/meson.build
@@ -0,0 +1,35 @@
+# FIXME: prevent install during main install, but not during test :/
+
+test_radixtree_sources = files(
+  'test_radixtree.c',
+)
+
+if host_system == 'windows'
+  test_radixtree_sources += rc_lib_gen.process(win32ver_rc, extra_args: [
+    '--NAME', 'test_radixtree',
+    '--FILEDESC', 'test_radixtree - test code for src/include//lib/radixtree.h',])
+endif
+
+test_radixtree = shared_module('test_radixtree',
+  test_radixtree_sources,
+  link_with: pgport_srv,
+  kwargs: pg_mod_args,
+)
+testprep_targets += test_radixtree
+
+install_data(
+  'test_radixtree.control',
+  'test_radixtree--1.0.sql',
+  kwargs: contrib_data_args,
+)
+
+tests += {
+  'name': 'test_radixtree',
+  'sd': meson.current_source_dir(),
+  'bd': meson.current_build_dir(),
+  'regress': {
+    'sql': [
+      'test_radixtree',
+    ],
+  },
+}
diff --git a/src/test/modules/test_radixtree/sql/test_radixtree.sql b/src/test/modules/test_radixtree/sql/test_radixtree.sql
new file mode 100644
index 0000000000..41ece5e9f5
--- /dev/null
+++ b/src/test/modules/test_radixtree/sql/test_radixtree.sql
@@ -0,0 +1,7 @@
+CREATE EXTENSION test_radixtree;
+
+--
+-- All the logic is in the test_radixtree() function. It will throw
+-- an error if something fails.
+--
+SELECT test_radixtree();
diff --git a/src/test/modules/test_radixtree/test_radixtree--1.0.sql b/src/test/modules/test_radixtree/test_radixtree--1.0.sql
new file mode 100644
index 0000000000..074a5a7ea7
--- /dev/null
+++ b/src/test/modules/test_radixtree/test_radixtree--1.0.sql
@@ -0,0 +1,8 @@
+/* src/test/modules/test_radixtree/test_radixtree--1.0.sql */
+
+-- complain if script is sourced in psql, rather than via CREATE EXTENSION
+\echo Use "CREATE EXTENSION test_radixtree" to load this file. \quit
+
+CREATE FUNCTION test_radixtree()
+RETURNS pg_catalog.void STRICT
+AS 'MODULE_PATHNAME' LANGUAGE C;
diff --git a/src/test/modules/test_radixtree/test_radixtree.c b/src/test/modules/test_radixtree/test_radixtree.c
new file mode 100644
index 0000000000..afe53382f3
--- /dev/null
+++ b/src/test/modules/test_radixtree/test_radixtree.c
@@ -0,0 +1,681 @@
+/*--------------------------------------------------------------------------
+ *
+ * test_radixtree.c
+ *		Test radixtree set data structure.
+ *
+ * Copyright (c) 2023, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/test/modules/test_radixtree/test_radixtree.c
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "common/pg_prng.h"
+#include "fmgr.h"
+#include "miscadmin.h"
+#include "nodes/bitmapset.h"
+#include "storage/block.h"
+#include "storage/itemptr.h"
+#include "storage/lwlock.h"
+#include "utils/memutils.h"
+#include "utils/timestamp.h"
+
+#define UINT64_HEX_FORMAT "%" INT64_MODIFIER "X"
+
+/*
+ * The tests pass with uint32, but build with warnings because the string
+ * format expects uint64.
+ */
+typedef uint64 TestValueType;
+
+/*
+ * If you enable this, the "pattern" tests will print information about
+ * how long populating, probing, and iterating the test set takes, and
+ * how much memory the test set consumed.  That can be used as
+ * micro-benchmark of various operations and input patterns (you might
+ * want to increase the number of values used in each of the test, if
+ * you do that, to reduce noise).
+ *
+ * The information is printed to the server's stderr, mostly because
+ * that's where MemoryContextStats() output goes.
+ */
+static const bool rt_test_stats = false;
+
+static int	rt_node_kind_fanouts[] = {
+	0,
+	4,							/* RT_NODE_KIND_4 */
+	32,							/* RT_NODE_KIND_32 */
+	125,						/* RT_NODE_KIND_125 */
+	256							/* RT_NODE_KIND_256 */
+};
+/*
+ * A struct to define a pattern of integers, for use with the test_pattern()
+ * function.
+ */
+typedef struct
+{
+	char	   *test_name;		/* short name of the test, for humans */
+	char	   *pattern_str;	/* a bit pattern */
+	uint64		spacing;		/* pattern repeats at this interval */
+	uint64		num_values;		/* number of integers to set in total */
+}			test_spec;
+
+/* Test patterns borrowed from test_integerset.c */
+static const test_spec test_specs[] = {
+	{
+		"all ones", "1111111111",
+		10, 1000000
+	},
+	{
+		"alternating bits", "0101010101",
+		10, 1000000
+	},
+	{
+		"clusters of ten", "1111111111",
+		10000, 1000000
+	},
+	{
+		"clusters of hundred",
+		"1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111",
+		10000, 1000000
+	},
+	{
+		"one-every-64k", "1",
+		65536, 1000000
+	},
+	{
+		"sparse", "100000000000000000000000000000001",
+		10000000, 1000000
+	},
+	{
+		"single values, distance > 2^32", "1",
+		UINT64CONST(10000000000), 100000
+	},
+	{
+		"clusters, distance > 2^32", "10101010",
+		UINT64CONST(10000000000), 1000000
+	},
+	{
+		"clusters, distance > 2^60", "10101010",
+		UINT64CONST(2000000000000000000),
+		23						/* can't be much higher than this, or we
+								 * overflow uint64 */
+	}
+};
+
+/* define the radix tree implementation to test */
+#define RT_PREFIX rt
+#define RT_SCOPE
+#define RT_DECLARE
+#define RT_DEFINE
+#define RT_USE_DELETE
+#define RT_VALUE_TYPE TestValueType
+/* #define RT_SHMEM */
+#include "lib/radixtree.h"
+
+
+/*
+ * Return the number of keys in the radix tree.
+ */
+static uint64
+rt_num_entries(rt_radix_tree *tree)
+{
+	return tree->ctl->num_keys;
+}
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(test_radixtree);
+
+static void
+test_empty(void)
+{
+	rt_radix_tree *radixtree;
+	rt_iter		*iter;
+	TestValueType		dummy;
+	uint64		key;
+	TestValueType		val;
+
+#ifdef RT_SHMEM
+	int			tranche_id = LWLockNewTrancheId();
+	dsa_area   *dsa;
+
+	LWLockRegisterTranche(tranche_id, "test_radix_tree");
+	dsa = dsa_create(tranche_id);
+
+	radixtree = rt_create(CurrentMemoryContext, dsa, tranche_id);
+#else
+	radixtree = rt_create(CurrentMemoryContext);
+#endif
+
+	if (rt_search(radixtree, 0, &dummy))
+		elog(ERROR, "rt_search on empty tree returned true");
+
+	if (rt_search(radixtree, 1, &dummy))
+		elog(ERROR, "rt_search on empty tree returned true");
+
+	if (rt_search(radixtree, PG_UINT64_MAX, &dummy))
+		elog(ERROR, "rt_search on empty tree returned true");
+
+	if (rt_delete(radixtree, 0))
+		elog(ERROR, "rt_delete on empty tree returned true");
+
+	if (rt_num_entries(radixtree) != 0)
+		elog(ERROR, "rt_num_entries on empty tree return non-zero");
+
+	iter = rt_begin_iterate(radixtree);
+
+	if (rt_iterate_next(iter, &key, &val))
+		elog(ERROR, "rt_itereate_next on empty tree returned true");
+
+	rt_end_iterate(iter);
+
+	rt_free(radixtree);
+
+#ifdef RT_SHMEM
+	dsa_detach(dsa);
+#endif
+}
+
+static void
+test_basic(int children, bool test_inner)
+{
+	rt_radix_tree	*radixtree;
+	uint64 *keys;
+	int	shift = test_inner ? 8 : 0;
+
+#ifdef RT_SHMEM
+	int			tranche_id = LWLockNewTrancheId();
+	dsa_area   *dsa;
+
+	LWLockRegisterTranche(tranche_id, "test_radix_tree");
+	dsa = dsa_create(tranche_id);
+#endif
+
+	elog(NOTICE, "testing basic operations with %s node %d",
+		 test_inner ? "inner" : "leaf", children);
+
+#ifdef RT_SHMEM
+	radixtree = rt_create(CurrentMemoryContext, dsa, tranche_id);
+#else
+	radixtree = rt_create(CurrentMemoryContext);
+#endif
+
+	/* prepare keys in order like 1, 32, 2, 31, 2, ... */
+	keys = palloc(sizeof(uint64) * children);
+	for (int i = 0; i < children; i++)
+	{
+		if (i % 2 == 0)
+			keys[i] = (uint64) ((i / 2) + 1) << shift;
+		else
+			keys[i] = (uint64) (children - (i / 2)) << shift;
+	}
+
+	/* insert keys */
+	for (int i = 0; i < children; i++)
+	{
+		if (rt_set(radixtree, keys[i], (TestValueType*) &keys[i]))
+			elog(ERROR, "new inserted key 0x" UINT64_HEX_FORMAT " is found ", keys[i]);
+	}
+
+	/* look up keys */
+	for (int i = 0; i < children; i++)
+	{
+		TestValueType value;
+
+		if (!rt_search(radixtree, keys[i], &value))
+			elog(ERROR, "could not find key 0x" UINT64_HEX_FORMAT, keys[i]);
+		if (value != (TestValueType) keys[i])
+			elog(ERROR, "rt_search returned 0x" UINT64_HEX_FORMAT ", expected " UINT64_HEX_FORMAT,
+				 value, (TestValueType) keys[i]);
+	}
+
+	/* update keys */
+	for (int i = 0; i < children; i++)
+	{
+		TestValueType update = keys[i] + 1;
+		if (!rt_set(radixtree, keys[i], (TestValueType*) &update))
+			elog(ERROR, "could not update key 0x" UINT64_HEX_FORMAT, keys[i]);
+	}
+
+	/* repeat deleting and inserting keys */
+	for (int i = 0; i < children; i++)
+	{
+		if (!rt_delete(radixtree, keys[i]))
+			elog(ERROR, "could not delete key 0x" UINT64_HEX_FORMAT, keys[i]);
+		if (rt_set(radixtree, keys[i], (TestValueType*) &keys[i]))
+			elog(ERROR, "new inserted key 0x" UINT64_HEX_FORMAT " is found ", keys[i]);
+	}
+
+	pfree(keys);
+	rt_free(radixtree);
+#ifdef RT_SHMEM
+	dsa_detach(dsa);
+#endif
+}
+
+/*
+ * Check if keys from start to end with the shift exist in the tree.
+ */
+static void
+check_search_on_node(rt_radix_tree *radixtree, uint8 shift, int start, int end,
+					 int incr)
+{
+	for (int i = start; i < end; i++)
+	{
+		uint64		key = ((uint64) i << shift);
+		TestValueType		val;
+
+		if (!rt_search(radixtree, key, &val))
+			elog(ERROR, "key 0x" UINT64_HEX_FORMAT " is not found on node-%d",
+				 key, end);
+		if (val != (TestValueType) key)
+			elog(ERROR, "rt_search with key 0x" UINT64_HEX_FORMAT " returns 0x" UINT64_HEX_FORMAT ", expected 0x" UINT64_HEX_FORMAT,
+				 key, val, key);
+	}
+}
+
+static void
+test_node_types_insert(rt_radix_tree *radixtree, uint8 shift, bool insert_asc)
+{
+	uint64		num_entries;
+	int		ninserted = 0;
+	int		start = insert_asc ? 0 : 256;
+	int 	incr = insert_asc ? 1 : -1;
+	int		end = insert_asc ? 256 : 0;
+	int		node_kind_idx = 1;
+
+	for (int i = start; i != end; i += incr)
+	{
+		uint64		key = ((uint64) i << shift);
+		bool		found;
+
+		found = rt_set(radixtree, key, (TestValueType*) &key);
+		if (found)
+			elog(ERROR, "newly inserted key 0x" UINT64_HEX_FORMAT " is found", key);
+
+		/*
+		 * After filling all slots in each node type, check if the values
+		 * are stored properly.
+		 */
+		if (ninserted == rt_node_kind_fanouts[node_kind_idx] - 1)
+		{
+			int check_start = insert_asc
+				? rt_node_kind_fanouts[node_kind_idx - 1]
+				: rt_node_kind_fanouts[node_kind_idx];
+			int check_end = insert_asc
+				? rt_node_kind_fanouts[node_kind_idx]
+				: rt_node_kind_fanouts[node_kind_idx - 1];
+
+			check_search_on_node(radixtree, shift, check_start, check_end, incr);
+			node_kind_idx++;
+		}
+
+		ninserted++;
+	}
+
+	num_entries = rt_num_entries(radixtree);
+
+	if (num_entries != 256)
+		elog(ERROR,
+			 "rt_num_entries returned " UINT64_FORMAT ", expected " UINT64_FORMAT,
+			 num_entries, UINT64CONST(256));
+}
+
+static void
+test_node_types_delete(rt_radix_tree *radixtree, uint8 shift)
+{
+	uint64		num_entries;
+
+	for (int i = 0; i < 256; i++)
+	{
+		uint64		key = ((uint64) i << shift);
+		bool		found;
+
+		found = rt_delete(radixtree, key);
+
+		if (!found)
+			elog(ERROR, "could not delete key 0x" UINT64_HEX_FORMAT, key);
+	}
+
+	num_entries = rt_num_entries(radixtree);
+
+	/* The tree must be empty */
+	if (num_entries != 0)
+		elog(ERROR,
+			 "rt_num_entries returned " UINT64_FORMAT ", expected " UINT64_FORMAT,
+			 num_entries, UINT64CONST(256));
+}
+
+/*
+ * Test for inserting and deleting key-value pairs to each node type at the given shift
+ * level.
+ */
+static void
+test_node_types(uint8 shift)
+{
+	rt_radix_tree *radixtree;
+
+#ifdef RT_SHMEM
+	int			tranche_id = LWLockNewTrancheId();
+	dsa_area   *dsa;
+
+	LWLockRegisterTranche(tranche_id, "test_radix_tree");
+	dsa = dsa_create(tranche_id);
+#endif
+
+	elog(NOTICE, "testing radix tree node types with shift \"%d\"", shift);
+
+#ifdef RT_SHMEM
+	radixtree = rt_create(CurrentMemoryContext, dsa, tranche_id);
+#else
+	radixtree = rt_create(CurrentMemoryContext);
+#endif
+
+	/*
+	 * Insert and search entries for every node type at the 'shift' level,
+	 * then delete all entries to make it empty, and insert and search entries
+	 * again.
+	 */
+	test_node_types_insert(radixtree, shift, true);
+	test_node_types_delete(radixtree, shift);
+	test_node_types_insert(radixtree, shift, false);
+
+	rt_free(radixtree);
+#ifdef RT_SHMEM
+	dsa_detach(dsa);
+#endif
+}
+
+/*
+ * Test with a repeating pattern, defined by the 'spec'.
+ */
+static void
+test_pattern(const test_spec * spec)
+{
+	rt_radix_tree *radixtree;
+	rt_iter    *iter;
+	MemoryContext radixtree_ctx;
+	TimestampTz starttime;
+	TimestampTz endtime;
+	uint64		n;
+	uint64		last_int;
+	uint64		ndeleted;
+	uint64		nbefore;
+	uint64		nafter;
+	int			patternlen;
+	uint64	   *pattern_values;
+	uint64		pattern_num_values;
+#ifdef RT_SHMEM
+	int			tranche_id = LWLockNewTrancheId();
+	dsa_area   *dsa;
+
+	LWLockRegisterTranche(tranche_id, "test_radix_tree");
+	dsa = dsa_create(tranche_id);
+#endif
+
+	elog(NOTICE, "testing radix tree with pattern \"%s\"", spec->test_name);
+	if (rt_test_stats)
+		fprintf(stderr, "-----\ntesting radix tree with pattern \"%s\"\n", spec->test_name);
+
+	/* Pre-process the pattern, creating an array of integers from it. */
+	patternlen = strlen(spec->pattern_str);
+	pattern_values = palloc(patternlen * sizeof(uint64));
+	pattern_num_values = 0;
+	for (int i = 0; i < patternlen; i++)
+	{
+		if (spec->pattern_str[i] == '1')
+			pattern_values[pattern_num_values++] = i;
+	}
+
+	/*
+	 * Allocate the radix tree.
+	 *
+	 * Allocate it in a separate memory context, so that we can print its
+	 * memory usage easily.
+	 */
+	radixtree_ctx = AllocSetContextCreate(CurrentMemoryContext,
+										  "radixtree test",
+										  ALLOCSET_SMALL_SIZES);
+	MemoryContextSetIdentifier(radixtree_ctx, spec->test_name);
+
+#ifdef RT_SHMEM
+	radixtree = rt_create(radixtree_ctx, dsa, tranche_id);
+#else
+	radixtree = rt_create(radixtree_ctx);
+#endif
+
+
+	/*
+	 * Add values to the set.
+	 */
+	starttime = GetCurrentTimestamp();
+
+	n = 0;
+	last_int = 0;
+	while (n < spec->num_values)
+	{
+		uint64		x = 0;
+
+		for (int i = 0; i < pattern_num_values && n < spec->num_values; i++)
+		{
+			bool		found;
+
+			x = last_int + pattern_values[i];
+
+			found = rt_set(radixtree, x, (TestValueType*) &x);
+
+			if (found)
+				elog(ERROR, "newly inserted key 0x" UINT64_HEX_FORMAT " found", x);
+
+			n++;
+		}
+		last_int += spec->spacing;
+	}
+
+	endtime = GetCurrentTimestamp();
+
+	if (rt_test_stats)
+		fprintf(stderr, "added " UINT64_FORMAT " values in %d ms\n",
+				spec->num_values, (int) (endtime - starttime) / 1000);
+
+	/*
+	 * Print stats on the amount of memory used.
+	 *
+	 * We print the usage reported by rt_memory_usage(), as well as the stats
+	 * from the memory context.  They should be in the same ballpark, but it's
+	 * hard to automate testing that, so if you're making changes to the
+	 * implementation, just observe that manually.
+	 */
+	if (rt_test_stats)
+	{
+		uint64		mem_usage;
+
+		/*
+		 * Also print memory usage as reported by rt_memory_usage().  It
+		 * should be in the same ballpark as the usage reported by
+		 * MemoryContextStats().
+		 */
+		mem_usage = rt_memory_usage(radixtree);
+		fprintf(stderr, "rt_memory_usage() reported " UINT64_FORMAT " (%0.2f bytes / integer)\n",
+				mem_usage, (double) mem_usage / spec->num_values);
+
+		MemoryContextStats(radixtree_ctx);
+	}
+
+	/* Check that rt_num_entries works */
+	n = rt_num_entries(radixtree);
+	if (n != spec->num_values)
+		elog(ERROR, "rt_num_entries returned " UINT64_FORMAT ", expected " UINT64_FORMAT, n, spec->num_values);
+
+	/*
+	 * Test random-access probes with rt_search()
+	 */
+	starttime = GetCurrentTimestamp();
+
+	for (n = 0; n < 100000; n++)
+	{
+		bool		found;
+		bool		expected;
+		uint64		x;
+		TestValueType		v;
+
+		/*
+		 * Pick next value to probe at random.  We limit the probes to the
+		 * last integer that we added to the set, plus an arbitrary constant
+		 * (1000).  There's no point in probing the whole 0 - 2^64 range, if
+		 * only a small part of the integer space is used.  We would very
+		 * rarely hit values that are actually in the set.
+		 */
+		x = pg_prng_uint64_range(&pg_global_prng_state, 0, last_int + 1000);
+
+		/* Do we expect this value to be present in the set? */
+		if (x >= last_int)
+			expected = false;
+		else
+		{
+			uint64		idx = x % spec->spacing;
+
+			if (idx >= patternlen)
+				expected = false;
+			else if (spec->pattern_str[idx] == '1')
+				expected = true;
+			else
+				expected = false;
+		}
+
+		/* Is it present according to rt_search() ? */
+		found = rt_search(radixtree, x, &v);
+
+		if (found != expected)
+			elog(ERROR, "mismatch at 0x" UINT64_HEX_FORMAT ": %d vs %d", x, found, expected);
+		if (found && (v != (TestValueType) x))
+			elog(ERROR, "found 0x" UINT64_HEX_FORMAT ", expected 0x" UINT64_HEX_FORMAT,
+				 v, x);
+	}
+	endtime = GetCurrentTimestamp();
+	if (rt_test_stats)
+		fprintf(stderr, "probed " UINT64_FORMAT " values in %d ms\n",
+				n, (int) (endtime - starttime) / 1000);
+
+	/*
+	 * Test iterator
+	 */
+	starttime = GetCurrentTimestamp();
+
+	iter = rt_begin_iterate(radixtree);
+	n = 0;
+	last_int = 0;
+	while (n < spec->num_values)
+	{
+		for (int i = 0; i < pattern_num_values && n < spec->num_values; i++)
+		{
+			uint64		expected = last_int + pattern_values[i];
+			uint64		x;
+			TestValueType		val;
+
+			if (!rt_iterate_next(iter, &x, &val))
+				break;
+
+			if (x != expected)
+				elog(ERROR,
+					 "iterate returned wrong key; got 0x" UINT64_HEX_FORMAT ", expected 0x" UINT64_HEX_FORMAT " at %d",
+					 x, expected, i);
+			if (val != (TestValueType) expected)
+				elog(ERROR,
+					 "iterate returned wrong value; got 0x" UINT64_HEX_FORMAT ", expected 0x" UINT64_HEX_FORMAT " at %d", x, expected, i);
+			n++;
+		}
+		last_int += spec->spacing;
+	}
+	endtime = GetCurrentTimestamp();
+	if (rt_test_stats)
+		fprintf(stderr, "iterated " UINT64_FORMAT " values in %d ms\n",
+				n, (int) (endtime - starttime) / 1000);
+
+	rt_end_iterate(iter);
+
+	if (n < spec->num_values)
+		elog(ERROR, "iterator stopped short after " UINT64_FORMAT " entries, expected " UINT64_FORMAT, n, spec->num_values);
+	if (n > spec->num_values)
+		elog(ERROR, "iterator returned " UINT64_FORMAT " entries, " UINT64_FORMAT " was expected", n, spec->num_values);
+
+	/*
+	 * Test random-access probes with rt_delete()
+	 */
+	starttime = GetCurrentTimestamp();
+
+	nbefore = rt_num_entries(radixtree);
+	ndeleted = 0;
+	for (n = 0; n < 1; n++)
+	{
+		bool		found;
+		uint64		x;
+		TestValueType		v;
+
+		/*
+		 * Pick next value to probe at random.  We limit the probes to the
+		 * last integer that we added to the set, plus an arbitrary constant
+		 * (1000).  There's no point in probing the whole 0 - 2^64 range, if
+		 * only a small part of the integer space is used.  We would very
+		 * rarely hit values that are actually in the set.
+		 */
+		x = pg_prng_uint64_range(&pg_global_prng_state, 0, last_int + 1000);
+
+		/* Is it present according to rt_search() ? */
+		found = rt_search(radixtree, x, &v);
+
+		if (!found)
+			continue;
+
+		/* If the key is found, delete it and check again */
+		if (!rt_delete(radixtree, x))
+			elog(ERROR, "could not delete key 0x" UINT64_HEX_FORMAT, x);
+		if (rt_search(radixtree, x, &v))
+			elog(ERROR, "found deleted key 0x" UINT64_HEX_FORMAT, x);
+		if (rt_delete(radixtree, x))
+			elog(ERROR, "deleted already-deleted key 0x" UINT64_HEX_FORMAT, x);
+
+		ndeleted++;
+	}
+	endtime = GetCurrentTimestamp();
+	if (rt_test_stats)
+		fprintf(stderr, "deleted " UINT64_FORMAT " values in %d ms\n",
+				ndeleted, (int) (endtime - starttime) / 1000);
+
+	nafter = rt_num_entries(radixtree);
+
+	/* Check that rt_num_entries works */
+	if ((nbefore - ndeleted) != nafter)
+		elog(ERROR, "rt_num_entries returned " UINT64_FORMAT ", expected " UINT64_FORMAT "after " UINT64_FORMAT " deletion",
+			 nafter, (nbefore - ndeleted), ndeleted);
+
+	rt_free(radixtree);
+	MemoryContextDelete(radixtree_ctx);
+#ifdef RT_SHMEM
+	dsa_detach(dsa);
+#endif
+}
+
+Datum
+test_radixtree(PG_FUNCTION_ARGS)
+{
+	test_empty();
+
+	for (int i = 1; i < lengthof(rt_node_kind_fanouts); i++)
+	{
+		test_basic(rt_node_kind_fanouts[i], false);
+		test_basic(rt_node_kind_fanouts[i], true);
+	}
+
+	for (int shift = 0; shift <= (64 - 8); shift += 8)
+		test_node_types(shift);
+
+	/* Test different test patterns, with lots of entries */
+	for (int i = 0; i < lengthof(test_specs); i++)
+		test_pattern(&test_specs[i]);
+
+	PG_RETURN_VOID();
+}
diff --git a/src/test/modules/test_radixtree/test_radixtree.control b/src/test/modules/test_radixtree/test_radixtree.control
new file mode 100644
index 0000000000..e53f2a3e0c
--- /dev/null
+++ b/src/test/modules/test_radixtree/test_radixtree.control
@@ -0,0 +1,4 @@
+comment = 'Test code for radix tree'
+default_version = '1.0'
+module_pathname = '$libdir/test_radixtree'
+relocatable = true
diff --git a/src/tools/pginclude/cpluspluscheck b/src/tools/pginclude/cpluspluscheck
index e52fe9f509..09fa6e7432 100755
--- a/src/tools/pginclude/cpluspluscheck
+++ b/src/tools/pginclude/cpluspluscheck
@@ -101,6 +101,12 @@ do
 	test "$f" = src/include/nodes/nodetags.h && continue
 	test "$f" = src/backend/nodes/nodetags.h && continue
 
+	# radixtree_*_impl.h cannot be included standalone: they are just code fragments.
+	test "$f" = src/include/lib/radixtree_delete_impl.h && continue
+	test "$f" = src/include/lib/radixtree_insert_impl.h && continue
+	test "$f" = src/include/lib/radixtree_iter_impl.h && continue
+	test "$f" = src/include/lib/radixtree_search_impl.h && continue
+
 	# These files are not meant to be included standalone, because
 	# they contain lists that might have multiple use-cases.
 	test "$f" = src/include/access/rmgrlist.h && continue
diff --git a/src/tools/pginclude/headerscheck b/src/tools/pginclude/headerscheck
index abbba7aa63..d4d2f1da03 100755
--- a/src/tools/pginclude/headerscheck
+++ b/src/tools/pginclude/headerscheck
@@ -96,6 +96,12 @@ do
 	test "$f" = src/include/nodes/nodetags.h && continue
 	test "$f" = src/backend/nodes/nodetags.h && continue
 
+	# radixtree_*_impl.h cannot be included standalone: they are just code fragments.
+	test "$f" = src/include/lib/radixtree_delete_impl.h && continue
+	test "$f" = src/include/lib/radixtree_insert_impl.h && continue
+	test "$f" = src/include/lib/radixtree_iter_impl.h && continue
+	test "$f" = src/include/lib/radixtree_search_impl.h && continue
+
 	# These files are not meant to be included standalone, because
 	# they contain lists that might have multiple use-cases.
 	test "$f" = src/include/access/rmgrlist.h && continue
-- 
2.31.1

