Making Bitmapsets be valid Nodes - Mailing list pgsql-hackers

Per the discussion at [1], it seems like it'd be a good idea to make
Bitmapsets into full-fledged, tagged Nodes, so that we could do things
like print or copy lists of them without special-case logic.  The
extra space for the NodeTag is basically free due to alignment
considerations, at least on 64-bit hardware.

Attached is a cleaned-up version of Amit's patch v24-0003 at [2].
I fixed the problems with not always tagging Bitmapsets, and changed
the outfuncs/readfuncs logic so that Bitmapsets still print exactly
as they did before (thus, this doesn't require a catversion bump).

As proof of concept, I removed the read_write_ignore labels from
RelOptInfo's unique_for_rels and non_unique_for_rels fields, and
got nice-looking debug printout:

      :unique_for_rels ((b 1))
      :non_unique_for_rels <>

I also removed some special-case code from indxpath.c because
list_member() can do the same thing now.  (There might be other
places that can be simplified; I didn't look very hard.)

It'd be possible to make Bitmapset fields be (mostly) not special cases
in the copy/equal/out/read support.  But I chose to leave that alone,
because it'd add a little runtime overhead for indirecting through the
generic support functions while not really saving any code space.

Barring objections, I'd like to go ahead and push this.

            regards, tom lane

[1] https://www.postgresql.org/message-id/94353655-c177-1f55-7afb-b2090de33341%40enterprisedb.com
[2] https://www.postgresql.org/message-id/CA%2BHiwqEYCLRZ2Boq_uK0pjLn_9b8XL-LmwKj7HN5kJOivUkYLg%40mail.gmail.com

diff --git a/src/backend/nodes/Makefile b/src/backend/nodes/Makefile
index 7450e191ee..d7b4261b47 100644
--- a/src/backend/nodes/Makefile
+++ b/src/backend/nodes/Makefile
@@ -52,6 +52,7 @@ node_headers = \
     commands/trigger.h \
     executor/tuptable.h \
     foreign/fdwapi.h \
+    nodes/bitmapset.h \
     nodes/extensible.h \
     nodes/lockoptions.h \
     nodes/replnodes.h \
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index 0a6c30e4eb..b7b274aeff 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -194,6 +194,7 @@ bms_make_singleton(int x)
     wordnum = WORDNUM(x);
     bitnum = BITNUM(x);
     result = (Bitmapset *) palloc0(BITMAPSET_SIZE(wordnum + 1));
+    result->type = T_Bitmapset;
     result->nwords = wordnum + 1;
     result->words[wordnum] = ((bitmapword) 1 << bitnum);
     return result;
@@ -852,6 +853,7 @@ bms_add_range(Bitmapset *a, int lower, int upper)
     if (a == NULL)
     {
         a = (Bitmapset *) palloc0(BITMAPSET_SIZE(uwordnum + 1));
+        a->type = T_Bitmapset;
         a->nwords = uwordnum + 1;
     }
     else if (uwordnum >= a->nwords)
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index e76fda8eba..84f5e2e6ad 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -160,6 +160,12 @@ _copyExtensibleNode(const ExtensibleNode *from)
     return newnode;
 }

+static Bitmapset *
+_copyBitmapset(const Bitmapset *from)
+{
+    return bms_copy(from);
+}
+

 /*
  * copyObjectImpl -- implementation of copyObject(); see nodes/nodes.h
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 0373aa30fe..b2f07da62e 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -145,6 +145,12 @@ _equalA_Const(const A_Const *a, const A_Const *b)
     return true;
 }

+static bool
+_equalBitmapset(const Bitmapset *a, const Bitmapset *b)
+{
+    return bms_equal(a, b);
+}
+
 /*
  * Lists are handled specially
  */
diff --git a/src/backend/nodes/gen_node_support.pl b/src/backend/nodes/gen_node_support.pl
index 81b8c184a9..d3f25299de 100644
--- a/src/backend/nodes/gen_node_support.pl
+++ b/src/backend/nodes/gen_node_support.pl
@@ -65,6 +65,7 @@ my @all_input_files = qw(
   commands/trigger.h
   executor/tuptable.h
   foreign/fdwapi.h
+  nodes/bitmapset.h
   nodes/extensible.h
   nodes/lockoptions.h
   nodes/replnodes.h
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 64c65f060b..f05e72f0dc 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -314,6 +314,9 @@ _outList(StringInfo str, const List *node)
  *       converts a bitmap set of integers
  *
  * Note: the output format is "(b int int ...)", similar to an integer List.
+ *
+ * We export this function for use by extensions that define extensible nodes.
+ * That's somewhat historical, though, because calling outNode() will work.
  */
 void
 outBitmapset(StringInfo str, const Bitmapset *bms)
@@ -844,6 +847,8 @@ outNode(StringInfo str, const void *obj)
         _outString(str, (String *) obj);
     else if (IsA(obj, BitString))
         _outBitString(str, (BitString *) obj);
+    else if (IsA(obj, Bitmapset))
+        outBitmapset(str, (Bitmapset *) obj);
     else
     {
         appendStringInfoChar(str, '{');
diff --git a/src/backend/nodes/read.c b/src/backend/nodes/read.c
index fe84f140ee..74d9d754d3 100644
--- a/src/backend/nodes/read.c
+++ b/src/backend/nodes/read.c
@@ -22,6 +22,7 @@
 #include <ctype.h>

 #include "common/string.h"
+#include "nodes/bitmapset.h"
 #include "nodes/pg_list.h"
 #include "nodes/readfuncs.h"
 #include "nodes/value.h"
@@ -347,6 +348,7 @@ nodeRead(const char *token, int tok_len)
                  * Could be an integer list:    (i int int ...)
                  * or an OID list:                (o int int ...)
                  * or an XID list:                (x int int ...)
+                 * or a bitmapset:                (b int int ...)
                  * or a list of nodes/values:    (node node ...)
                  *----------
                  */
@@ -372,6 +374,7 @@ nodeRead(const char *token, int tok_len)
                                  tok_len, token);
                         l = lappend_int(l, val);
                     }
+                    result = (Node *) l;
                 }
                 else if (tok_len == 1 && token[0] == 'o')
                 {
@@ -392,6 +395,7 @@ nodeRead(const char *token, int tok_len)
                                  tok_len, token);
                         l = lappend_oid(l, val);
                     }
+                    result = (Node *) l;
                 }
                 else if (tok_len == 1 && token[0] == 'x')
                 {
@@ -412,6 +416,30 @@ nodeRead(const char *token, int tok_len)
                                  tok_len, token);
                         l = lappend_xid(l, val);
                     }
+                    result = (Node *) l;
+                }
+                else if (tok_len == 1 && token[0] == 'b')
+                {
+                    /* Bitmapset -- see also _readBitmapset() */
+                    Bitmapset  *bms = NULL;
+
+                    for (;;)
+                    {
+                        int            val;
+                        char       *endptr;
+
+                        token = pg_strtok(&tok_len);
+                        if (token == NULL)
+                            elog(ERROR, "unterminated Bitmapset structure");
+                        if (tok_len == 1 && token[0] == ')')
+                            break;
+                        val = (int) strtol(token, &endptr, 10);
+                        if (endptr != token + tok_len)
+                            elog(ERROR, "unrecognized integer: \"%.*s\"",
+                                 tok_len, token);
+                        bms = bms_add_member(bms, val);
+                    }
+                    result = (Node *) bms;
                 }
                 else
                 {
@@ -426,8 +454,8 @@ nodeRead(const char *token, int tok_len)
                         if (token == NULL)
                             elog(ERROR, "unterminated List structure");
                     }
+                    result = (Node *) l;
                 }
-                result = (Node *) l;
                 break;
             }
         case RIGHT_PAREN:
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index b4ff855f7c..23776367c5 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -194,6 +194,10 @@ nullable_string(const char *token, int length)

 /*
  * _readBitmapset
+ *
+ * Note: this code is used in contexts where we know that a Bitmapset
+ * is expected.  There is equivalent code in nodeRead() that can read a
+ * Bitmapset when we come across one in other contexts.
  */
 static Bitmapset *
 _readBitmapset(void)
@@ -234,7 +238,8 @@ _readBitmapset(void)
 }

 /*
- * for use by extensions which define extensible nodes
+ * We export this function for use by extensions that define extensible nodes.
+ * That's somewhat historical, though, because calling nodeRead() will work.
  */
 Bitmapset *
 readBitmapset(void)
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 77f3f81bcb..914bfd90bc 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -99,7 +99,6 @@ static void get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
                                  List **considered_relids);
 static bool eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
                                 List *indexjoinclauses);
-static bool bms_equal_any(Relids relids, List *relids_list);
 static void get_index_paths(PlannerInfo *root, RelOptInfo *rel,
                             IndexOptInfo *index, IndexClauseSet *clauses,
                             List **bitindexpaths);
@@ -370,8 +369,8 @@ create_index_paths(PlannerInfo *root, RelOptInfo *rel)
             Path       *path = (Path *) lfirst(lc);
             Relids        required_outer = PATH_REQ_OUTER(path);

-            if (!bms_equal_any(required_outer, all_path_outers))
-                all_path_outers = lappend(all_path_outers, required_outer);
+            all_path_outers = list_append_unique(all_path_outers,
+                                                 required_outer);
         }

         /* Now, for each distinct parameterization set ... */
@@ -517,7 +516,7 @@ consider_index_join_outer_rels(PlannerInfo *root, RelOptInfo *rel,
         int            num_considered_relids;

         /* If we already tried its relids set, no need to do so again */
-        if (bms_equal_any(clause_relids, *considered_relids))
+        if (list_member(*considered_relids, clause_relids))
             continue;

         /*
@@ -612,7 +611,7 @@ get_join_index_paths(PlannerInfo *root, RelOptInfo *rel,
     int            indexcol;

     /* If we already considered this relids set, don't repeat the work */
-    if (bms_equal_any(relids, *considered_relids))
+    if (list_member(*considered_relids, relids))
         return;

     /* Identify indexclauses usable with this relids set */
@@ -694,25 +693,6 @@ eclass_already_used(EquivalenceClass *parent_ec, Relids oldrelids,
     return false;
 }

-/*
- * bms_equal_any
- *        True if relids is bms_equal to any member of relids_list
- *
- * Perhaps this should be in bitmapset.c someday.
- */
-static bool
-bms_equal_any(Relids relids, List *relids_list)
-{
-    ListCell   *lc;
-
-    foreach(lc, relids_list)
-    {
-        if (bms_equal(relids, (Relids) lfirst(lc)))
-            return true;
-    }
-    return false;
-}
-

 /*
  * get_index_paths
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 75b5ce1a8e..2792281658 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -20,6 +20,8 @@
 #ifndef BITMAPSET_H
 #define BITMAPSET_H

+#include "nodes/nodes.h"
+
 /*
  * Forward decl to save including pg_list.h
  */
@@ -48,6 +50,9 @@ typedef int32 signedbitmapword; /* must be the matching signed type */

 typedef struct Bitmapset
 {
+    pg_node_attr(custom_copy_equal, special_read_write)
+
+    NodeTag        type;
     int            nwords;            /* number of words in array */
     bitmapword    words[FLEXIBLE_ARRAY_MEMBER];    /* really [nwords] */
 } Bitmapset;
diff --git a/src/include/nodes/meson.build b/src/include/nodes/meson.build
index b7df232081..e63881086e 100644
--- a/src/include/nodes/meson.build
+++ b/src/include/nodes/meson.build
@@ -13,6 +13,7 @@ node_support_input_i = [
   'commands/trigger.h',
   'executor/tuptable.h',
   'foreign/fdwapi.h',
+  'nodes/bitmapset.h',
   'nodes/extensible.h',
   'nodes/lockoptions.h',
   'nodes/replnodes.h',
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 09342d128d..a544b313d3 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -911,13 +911,11 @@ typedef struct RelOptInfo

     /*
      * cache space for remembering if we have proven this relation unique
-     *
-     * can't print unique_for_rels/non_unique_for_rels; BMSes aren't Nodes
      */
     /* known unique for these other relid set(s) */
-    List       *unique_for_rels pg_node_attr(read_write_ignore);
+    List       *unique_for_rels;
     /* known not unique for these set(s) */
-    List       *non_unique_for_rels pg_node_attr(read_write_ignore);
+    List       *non_unique_for_rels;

     /*
      * used by various scans and joins: