Thread: Allow pageinspect's bt_page_stats function to return a set of rows instead of a single row

Hi,

Hello Hackers,

While working on one of my blogs on the B-Tree indexes, I needed to look at a range of B-Tree page statistics. So the goto solution was to use pageinspect. However, reviewing stats for multiple pages meant issuing multiple queries.

FWIW, I think you could also rely on generate_series()

I felt that there's an opportunity for improvement in the extension by extending the API to output the statistics for multiple pages with a single query.

That attached patch is based on the master branch. It makes the following changes to the pageinspect contrib module:
- Updates bt_page_stats_internal function to accept 3 arguments instead of 2.
- The function now uses SRF macros to return a set rather than a single row. The function call now requires specifying column names.

The extension version is bumped to 1.11 (PAGEINSPECT_V1_11).
To maintain backward compatibility, for versions below 1.11, the multi-call mechanism is ended to keep the old behavior consistent.

Regression test cases for the module are updated as well as part of this change. Here is a subset of queries that are added to the btree.sql test case file for pageinspect.

----

CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
CREATE INDEX test2_col1_idx ON test2(col1);
SELECT * FROM bt_page_stats('test2_col1_idx', 1, 2);

For example, this could be written as:

select * from
generate_series(1, 2) blkno ,
bt_page_stats('test2_col1_idx',blkno::int);

Or, if one wants to inspect to whole relation, something like:

select * from
generate_series(1, pg_relation_size('test2_col1_idx'::regclass::text) / 8192 - 1) blkno ,
bt_page_stats('test2_col1_idx',blkno::int);

Regards,

Bertrand

On Mon, Jun 27, 2022 at 1:40 PM Drouvot, Bertrand <bdrouvot@amazon.com> wrote:
>
> Hi,
>
> On 6/27/22 9:31 AM, Hamid Akhtar wrote:
>
>
> Hello Hackers,
>
> While working on one of my blogs on the B-Tree indexes, I needed to look at a range of B-Tree page statistics. So the
gotosolution was to use pageinspect. However, reviewing stats for multiple pages meant issuing multiple queries.
 

+1 to improve the API.

> I felt that there's an opportunity for improvement in the extension by extending the API to output the statistics for
multiplepages with a single query.
 
>
> That attached patch is based on the master branch. It makes the following changes to the pageinspect contrib module:
> - Updates bt_page_stats_internal function to accept 3 arguments instead of 2.
> - The function now uses SRF macros to return a set rather than a single row. The function call now requires
specifyingcolumn names.
 
>
> The extension version is bumped to 1.11 (PAGEINSPECT_V1_11).
> To maintain backward compatibility, for versions below 1.11, the multi-call mechanism is ended to keep the old
behaviorconsistent.
 
>
> Regression test cases for the module are updated as well as part of this change. Here is a subset of queries that are
addedto the btree.sql test case file for pageinspect.
 
>
> ----
> CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
> CREATE INDEX test2_col1_idx ON test2(col1);
> SELECT * FROM bt_page_stats('test2_col1_idx', 1, 2);
>
> For example, this could be written as:
>
> select * from
> generate_series(1, 2) blkno ,
> bt_page_stats('test2_col1_idx',blkno::int);
>
> Or, if one wants to inspect to whole relation, something like:
>
> select * from
> generate_series(1, pg_relation_size('test2_col1_idx'::regclass::text) / 8192 - 1) blkno ,
> bt_page_stats('test2_col1_idx',blkno::int);

Good one. But not all may know the alternatives. Do we have any
difference in the execution times for the above query vs the new
function introduced in the v1 patch? If there's not much difference, I
would suggest adding an SQL function around the generate_series
approach in the pageinspect extension for better and easier usability.

Regards,
Bharath Rupireddy.

On Thu, Jun 30, 2022 at 1:54 PM Hamid Akhtar <hamid.akhtar@gmail.com> wrote:
>
>> Do we have any
>> difference in the execution times for the above query vs the new
>> function introduced in the v1 patch? If there's not much difference, I
>> would suggest adding an SQL function around the generate_series
>> approach in the pageinspect extension for better and easier usability.
>
>
> Based on some basic SQL execution time comparison of the two approaches, I see that the API change, on average, is
around40% faster than the SQL.
 
>
> CREATE TABLE test2 AS (SELECT generate_series(1, 5000000) AS col1);
> CREATE INDEX test2_col1_idx ON test2(col1);
>
> EXPLAIN ANALYZE
> SELECT * FROM bt_page_stats('test2_col1_idx', 1, 5000);
>
> EXPLAIN ANALYZE
> SELECT * FROM GENERATE_SERIES(1, 5000) blkno, bt_page_stats('test2_col1_idx',blkno::int);
>
> For me, the API change returns back the data in around 74ms whereas the SQL returns it in 102ms. So considering this
andas you mentioned, the alternative may not be that obvious to everyone, it is a fair improvement.
 

I'm wondering what happens with a bit of huge data and different test
cases each test case executed, say, 2 or 3 times.

If the difference in execution times is always present, then the API
approach or changing the core function would make more sense.

Regards,
Bharath Rupireddy.

Hi,

On Mon, 27 Jun 2022 at 15:52, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> wrote:

On Mon, Jun 27, 2022 at 1:40 PM Drouvot, Bertrand <bdrouvot@amazon.com> wrote:
>
> Hi,
>
> On 6/27/22 9:31 AM, Hamid Akhtar wrote:
>
>
> Hello Hackers,
>
> While working on one of my blogs on the B-Tree indexes, I needed to look at a range of B-Tree page statistics. So the goto solution was to use pageinspect. However, reviewing stats for multiple pages meant issuing multiple queries.

+1 to improve the API.

I think it makes sense too.

But what about the other pageinspect's functions that also use a single blkno as parameter? Should not the patch also takes care of them?

Regards,

Bertrand

Hamid Akhtar <hamid.akhtar@gmail.com> writes:
> That attached patch is based on the master branch. It makes the following
> changes to the pageinspect contrib module:
> - Updates bt_page_stats_internal function to accept 3 arguments instead of
> 2.
> - The function now uses SRF macros to return a set rather than a single
> row. The function call now requires specifying column names.

FWIW, I think you'd be way better off changing the function name, say
to bt_multi_page_stats().  Overloading the name this way is going to
lead to great confusion, e.g. somebody who fat-fingers the number of
output arguments in a JDBC call could see confusing results due to
invoking the wrong one of the two functions.  Also, I'm not quite sure
what you mean by "The function call now requires specifying column
names", but it doesn't sound like an acceptable restriction from a
compatibility standpoint.  If a different name dodges that issue then
it's clearly a better way.

            regards, tom lane

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       tested, passed
Spec compliant:           not tested
Documentation:            not tested

Looks good to me.

The new status of this patch is: Ready for Committer

Hamid Akhtar <hamid.akhtar@gmail.com> writes:
> Attached is the rebased version of the patch
> (pageinspect_btree_multipagestats_03.patch) for the master branch.

I looked through this and cleaned up the code a little (attached).
There are still some issues before it could be considered committable:

1. Where's the documentation update?

2. As this stands, there's no nice way to ask for "all the pages".
If you specify a page count that's even one too large, you get an
error.  I think there's room for an easier-to-use way to do that.
We could say that the thing just silently stops at the last page,
so that you just need to write a large page count.  Or maybe it'd
be better to define a zero or negative page count as "all the rest",
while still insisting that a positive count refer to real pages.

3. I think it's highly likely that the new test case is not portable.
In particular a machine with MAXALIGN 4 would be likely to put a
different number of tuples per page, or do the page split differently
so that the page with fewer index tuples isn't page 3.  Unfortunately
I don't seem to have a working setup like that right at the moment
to verify; but I'd counsel trying this inside a VM or something to
see if it's actually likely to survive on the buildfarm.  I'm not
sure, but making the indexed column be int8 instead of int4 might
reduce the risks here.

            regards, tom lane

diff --git a/contrib/pageinspect/Makefile b/contrib/pageinspect/Makefile
index 5c0736564a..069683caf6 100644
--- a/contrib/pageinspect/Makefile
+++ b/contrib/pageinspect/Makefile
@@ -13,7 +13,9 @@ OBJS = \
     rawpage.o

 EXTENSION = pageinspect
-DATA =  pageinspect--1.9--1.10.sql pageinspect--1.8--1.9.sql \
+DATA = \
+    pageinspect--1.10--1.11.sql \
+    pageinspect--1.9--1.10.sql pageinspect--1.8--1.9.sql \
     pageinspect--1.7--1.8.sql pageinspect--1.6--1.7.sql \
     pageinspect--1.5.sql pageinspect--1.5--1.6.sql \
     pageinspect--1.4--1.5.sql pageinspect--1.3--1.4.sql \
diff --git a/contrib/pageinspect/btreefuncs.c b/contrib/pageinspect/btreefuncs.c
index 9375d55e14..f52a6ac87e 100644
--- a/contrib/pageinspect/btreefuncs.c
+++ b/contrib/pageinspect/btreefuncs.c
@@ -46,6 +46,7 @@ PG_FUNCTION_INFO_V1(bt_page_items);
 PG_FUNCTION_INFO_V1(bt_page_items_bytea);
 PG_FUNCTION_INFO_V1(bt_page_stats_1_9);
 PG_FUNCTION_INFO_V1(bt_page_stats);
+PG_FUNCTION_INFO_V1(bt_multi_page_stats);

 #define IS_INDEX(r) ((r)->rd_rel->relkind == RELKIND_INDEX)
 #define IS_BTREE(r) ((r)->rd_rel->relam == BTREE_AM_OID)
@@ -80,6 +81,28 @@ typedef struct BTPageStat
     BTCycleId    btpo_cycleid;
 } BTPageStat;

+/*
+ * cross-call data structure for SRF for page stats
+ */
+typedef struct ua_page_stats
+{
+    Oid            relid;
+    int64        blkno;
+    int64        blk_count;
+} ua_page_stats;
+
+/*
+ * cross-call data structure for SRF for page items
+ */
+typedef struct ua_page_items
+{
+    Page        page;
+    OffsetNumber offset;
+    bool        leafpage;
+    bool        rightmost;
+    TupleDesc    tupd;
+} ua_page_items;
+

 /* -------------------------------------------------
  * GetBTPageStatistics()
@@ -177,34 +200,15 @@ GetBTPageStatistics(BlockNumber blkno, Buffer buffer, BTPageStat *stat)
 }

 /* -----------------------------------------------
- * bt_page_stats()
+ * bt_index_block_validate()
  *
- * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
+ * Validate index type is btree and block number
+ * is within a valid block number range.
  * -----------------------------------------------
  */
-static Datum
-bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+static void
+bt_index_block_validate(Relation rel, int64 blkno)
 {
-    text       *relname = PG_GETARG_TEXT_PP(0);
-    int64        blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
-    Buffer        buffer;
-    Relation    rel;
-    RangeVar   *relrv;
-    Datum        result;
-    HeapTuple    tuple;
-    TupleDesc    tupleDesc;
-    int            j;
-    char       *values[11];
-    BTPageStat    stat;
-
-    if (!superuser())
-        ereport(ERROR,
-                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-                 errmsg("must be superuser to use pageinspect functions")));
-
-    relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
-    rel = relation_openrv(relrv, AccessShareLock);
-
     if (!IS_INDEX(rel) || !IS_BTREE(rel))
         ereport(ERROR,
                 (errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -232,6 +236,39 @@ bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
                  errmsg("block 0 is a meta page")));

     CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+}
+
+/* -----------------------------------------------
+ * bt_page_stats()
+ *
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1);
+ * Arguments are index relation name and block number
+ * -----------------------------------------------
+ */
+static Datum
+bt_page_stats_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
+{
+    text       *relname = PG_GETARG_TEXT_PP(0);
+    int64        blkno = (ext_version == PAGEINSPECT_V1_8 ? PG_GETARG_UINT32(1) : PG_GETARG_INT64(1));
+    Buffer        buffer;
+    Relation    rel;
+    RangeVar   *relrv;
+    Datum        result;
+    HeapTuple    tuple;
+    TupleDesc    tupleDesc;
+    int            j;
+    char       *values[11];
+    BTPageStat    stat;
+
+    if (!superuser())
+        ereport(ERROR,
+                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+                 errmsg("must be superuser to use pageinspect functions")));
+
+    relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+    rel = relation_openrv(relrv, AccessShareLock);
+
+    bt_index_block_validate(rel, blkno);

     buffer = ReadBuffer(rel, blkno);
     LockBuffer(buffer, BUFFER_LOCK_SHARE);
@@ -284,17 +321,134 @@ bt_page_stats(PG_FUNCTION_ARGS)
 }


-/*
- * cross-call data structure for SRF
+/* -----------------------------------------------
+ * bt_multi_page_stats()
+ *
+ * Usage: SELECT * FROM bt_page_stats('t1_pkey', 1, 2);
+ * Arguments are index relation name, first block number, number of blocks
+ * -----------------------------------------------
  */
-struct user_args
+Datum
+bt_multi_page_stats(PG_FUNCTION_ARGS)
 {
-    Page        page;
-    OffsetNumber offset;
-    bool        leafpage;
-    bool        rightmost;
-    TupleDesc    tupd;
-};
+    Relation    rel;
+    ua_page_stats *uargs;
+    FuncCallContext *fctx;
+    MemoryContext mctx;
+
+    if (!superuser())
+        ereport(ERROR,
+                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+                 errmsg("must be superuser to use pageinspect functions")));
+
+    if (SRF_IS_FIRSTCALL())
+    {
+        text       *relname = PG_GETARG_TEXT_PP(0);
+        int64        blkno = PG_GETARG_INT64(1);
+        int64        blk_count = PG_GETARG_INT64(2);
+        RangeVar   *relrv;
+
+        fctx = SRF_FIRSTCALL_INIT();
+
+        relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
+        rel = relation_openrv(relrv, AccessShareLock);
+
+        /* Check that rel is a valid btree index and 1st block number is OK */
+        bt_index_block_validate(rel, blkno);
+
+        /* Save arguments for reuse */
+        mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);
+
+        uargs = palloc(sizeof(ua_page_stats));
+
+        uargs->relid = RelationGetRelid(rel);
+        uargs->blkno = blkno;
+        uargs->blk_count = blk_count;
+
+        fctx->user_fctx = uargs;
+
+        MemoryContextSwitchTo(mctx);
+
+        /*
+         * To avoid possibly leaking a relcache reference if the SRF isn't run
+         * to completion, we close and re-open the index rel each time
+         * through, using the index's OID for re-opens to ensure we get the
+         * same rel.  Keep the AccessShareLock though, to ensure it doesn't go
+         * away underneath us.
+         */
+        relation_close(rel, NoLock);
+    }
+
+    fctx = SRF_PERCALL_SETUP();
+    uargs = fctx->user_fctx;
+
+    /* We need to fetch next block statistics */
+    if (uargs->blk_count > 0)
+    {
+        Buffer        buffer;
+        Datum        result;
+        HeapTuple    tuple;
+        int            j;
+        char       *values[11];
+        BTPageStat    stat;
+        TupleDesc    tupleDesc;
+
+        /* We should have lock already */
+        rel = relation_open(uargs->relid, NoLock);
+
+        /*
+         * Check that the next block number is valid --- we could have stepped
+         * off the end, or index could have gotten shorter.
+         */
+        CHECK_RELATION_BLOCK_RANGE(rel, uargs->blkno);
+
+        buffer = ReadBuffer(rel, uargs->blkno);
+        LockBuffer(buffer, BUFFER_LOCK_SHARE);
+
+        /* keep compiler quiet */
+        stat.btpo_prev = stat.btpo_next = InvalidBlockNumber;
+        stat.btpo_flags = stat.free_size = stat.avg_item_size = 0;
+
+        GetBTPageStatistics(uargs->blkno, buffer, &stat);
+
+        UnlockReleaseBuffer(buffer);
+        relation_close(rel, NoLock);
+
+        /* Build a tuple descriptor for our result type */
+        if (get_call_result_type(fcinfo, NULL, &tupleDesc) != TYPEFUNC_COMPOSITE)
+            elog(ERROR, "return type must be a row type");
+
+        j = 0;
+        values[j++] = psprintf("%u", stat.blkno);
+        values[j++] = psprintf("%c", stat.type);
+        values[j++] = psprintf("%u", stat.live_items);
+        values[j++] = psprintf("%u", stat.dead_items);
+        values[j++] = psprintf("%u", stat.avg_item_size);
+        values[j++] = psprintf("%u", stat.page_size);
+        values[j++] = psprintf("%u", stat.free_size);
+        values[j++] = psprintf("%u", stat.btpo_prev);
+        values[j++] = psprintf("%u", stat.btpo_next);
+        values[j++] = psprintf("%u", stat.btpo_level);
+        values[j++] = psprintf("%d", stat.btpo_flags);
+
+        /* Construct tuple to be returned */
+        tuple = BuildTupleFromCStrings(TupleDescGetAttInMetadata(tupleDesc),
+                                       values);
+
+        result = HeapTupleGetDatum(tuple);
+
+        /*
+         * Move to the next block number and decrement the number of blocks
+         * still to be fetched
+         */
+        uargs->blkno++;
+        uargs->blk_count--;
+
+        SRF_RETURN_NEXT(fctx, result);
+    }
+
+    SRF_RETURN_DONE(fctx);
+}

 /*-------------------------------------------------------
  * bt_page_print_tuples()
@@ -303,7 +457,7 @@ struct user_args
  * ------------------------------------------------------
  */
 static Datum
-bt_page_print_tuples(struct user_args *uargs)
+bt_page_print_tuples(ua_page_items *uargs)
 {
     Page        page = uargs->page;
     OffsetNumber offset = uargs->offset;
@@ -453,7 +607,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
     Datum        result;
     FuncCallContext *fctx;
     MemoryContext mctx;
-    struct user_args *uargs;
+    ua_page_items *uargs;

     if (!superuser())
         ereport(ERROR,
@@ -473,33 +627,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
         relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
         rel = relation_openrv(relrv, AccessShareLock);

-        if (!IS_INDEX(rel) || !IS_BTREE(rel))
-            ereport(ERROR,
-                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
-                     errmsg("\"%s\" is not a %s index",
-                            RelationGetRelationName(rel), "btree")));
-
-        /*
-         * Reject attempts to read non-local temporary relations; we would be
-         * likely to get wrong data since we have no visibility into the
-         * owning session's local buffers.
-         */
-        if (RELATION_IS_OTHER_TEMP(rel))
-            ereport(ERROR,
-                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-                     errmsg("cannot access temporary tables of other sessions")));
-
-        if (blkno < 0 || blkno > MaxBlockNumber)
-            ereport(ERROR,
-                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-                     errmsg("invalid block number")));
-
-        if (blkno == 0)
-            ereport(ERROR,
-                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-                     errmsg("block 0 is a meta page")));
-
-        CHECK_RELATION_BLOCK_RANGE(rel, blkno);
+        bt_index_block_validate(rel, blkno);

         buffer = ReadBuffer(rel, blkno);
         LockBuffer(buffer, BUFFER_LOCK_SHARE);
@@ -511,7 +639,7 @@ bt_page_items_internal(PG_FUNCTION_ARGS, enum pageinspect_version ext_version)
          */
         mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

-        uargs = palloc(sizeof(struct user_args));
+        uargs = palloc(sizeof(ua_page_items));

         uargs->page = palloc(BLCKSZ);
         memcpy(uargs->page, BufferGetPage(buffer), BLCKSZ);
@@ -587,7 +715,7 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
     bytea       *raw_page = PG_GETARG_BYTEA_P(0);
     Datum        result;
     FuncCallContext *fctx;
-    struct user_args *uargs;
+    ua_page_items *uargs;

     if (!superuser())
         ereport(ERROR,
@@ -603,7 +731,7 @@ bt_page_items_bytea(PG_FUNCTION_ARGS)
         fctx = SRF_FIRSTCALL_INIT();
         mctx = MemoryContextSwitchTo(fctx->multi_call_memory_ctx);

-        uargs = palloc(sizeof(struct user_args));
+        uargs = palloc(sizeof(ua_page_items));

         uargs->page = get_page_from_raw(raw_page);

diff --git a/contrib/pageinspect/expected/btree.out b/contrib/pageinspect/expected/btree.out
index 035a81a759..de747f1751 100644
--- a/contrib/pageinspect/expected/btree.out
+++ b/contrib/pageinspect/expected/btree.out
@@ -34,6 +34,118 @@ btpo_flags    | 3

 SELECT * FROM bt_page_stats('test1_a_idx', 2);
 ERROR:  block number out of range
+-- bt_multi_page_stats() function returns a set of records of page statistics.
+CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
+CREATE INDEX test2_col1_idx ON test2(col1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 0, 1);
+ERROR:  block 0 is a meta page
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, -1);
+(0 rows)
+
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 0);
+(0 rows)
+
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 2);
+-[ RECORD 1 ]-+-----
+blkno         | 1
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 0
+btpo_next     | 2
+btpo_level    | 0
+btpo_flags    | 1
+-[ RECORD 2 ]-+-----
+blkno         | 2
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 1
+btpo_next     | 4
+btpo_level    | 0
+btpo_flags    | 1
+
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 2, 6);
+-[ RECORD 1 ]-+-----
+blkno         | 2
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 1
+btpo_next     | 4
+btpo_level    | 0
+btpo_flags    | 1
+-[ RECORD 2 ]-+-----
+blkno         | 3
+type          | r
+live_items    | 14
+dead_items    | 0
+avg_item_size | 15
+page_size     | 8192
+free_size     | 7876
+btpo_prev     | 0
+btpo_next     | 0
+btpo_level    | 1
+btpo_flags    | 2
+-[ RECORD 3 ]-+-----
+blkno         | 4
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 2
+btpo_next     | 5
+btpo_level    | 0
+btpo_flags    | 1
+-[ RECORD 4 ]-+-----
+blkno         | 5
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 4
+btpo_next     | 6
+btpo_level    | 0
+btpo_flags    | 1
+-[ RECORD 5 ]-+-----
+blkno         | 6
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 5
+btpo_next     | 7
+btpo_level    | 0
+btpo_flags    | 1
+-[ RECORD 6 ]-+-----
+blkno         | 7
+type          | l
+live_items    | 367
+dead_items    | 0
+avg_item_size | 16
+page_size     | 8192
+free_size     | 808
+btpo_prev     | 6
+btpo_next     | 8
+btpo_level    | 0
+btpo_flags    | 1
+
+DROP TABLE test2;
 SELECT * FROM bt_page_items('test1_a_idx', -1);
 ERROR:  invalid block number
 SELECT * FROM bt_page_items('test1_a_idx', 0);
diff --git a/contrib/pageinspect/pageinspect--1.10--1.11.sql b/contrib/pageinspect/pageinspect--1.10--1.11.sql
new file mode 100644
index 0000000000..976d029de9
--- /dev/null
+++ b/contrib/pageinspect/pageinspect--1.10--1.11.sql
@@ -0,0 +1,23 @@
+/* contrib/pageinspect/pageinspect--1.10--1.11.sql */
+
+-- complain if script is sourced in psql, rather than via ALTER EXTENSION
+\echo Use "ALTER EXTENSION pageinspect UPDATE TO '1.11'" to load this file. \quit
+
+--
+-- bt_multi_page_stats()
+--
+CREATE FUNCTION bt_multi_page_stats(IN relname text, IN blkno int8, IN blk_count int8,
+    OUT blkno int8,
+    OUT type "char",
+    OUT live_items int4,
+    OUT dead_items int4,
+    OUT avg_item_size int4,
+    OUT page_size int4,
+    OUT free_size int4,
+    OUT btpo_prev int8,
+    OUT btpo_next int8,
+    OUT btpo_level int8,
+    OUT btpo_flags int4)
+RETURNS SETOF record
+AS 'MODULE_PATHNAME', 'bt_multi_page_stats'
+LANGUAGE C STRICT PARALLEL SAFE;
diff --git a/contrib/pageinspect/pageinspect.control b/contrib/pageinspect/pageinspect.control
index 7cdf37913d..f277413dd8 100644
--- a/contrib/pageinspect/pageinspect.control
+++ b/contrib/pageinspect/pageinspect.control
@@ -1,5 +1,5 @@
 # pageinspect extension
 comment = 'inspect the contents of database pages at a low level'
-default_version = '1.10'
+default_version = '1.11'
 module_pathname = '$libdir/pageinspect'
 relocatable = true
diff --git a/contrib/pageinspect/sql/btree.sql b/contrib/pageinspect/sql/btree.sql
index 1f554f0f67..9a959142cd 100644
--- a/contrib/pageinspect/sql/btree.sql
+++ b/contrib/pageinspect/sql/btree.sql
@@ -11,6 +11,16 @@ SELECT * FROM bt_page_stats('test1_a_idx', 0);
 SELECT * FROM bt_page_stats('test1_a_idx', 1);
 SELECT * FROM bt_page_stats('test1_a_idx', 2);

+-- bt_multi_page_stats() function returns a set of records of page statistics.
+CREATE TABLE test2 AS (SELECT generate_series(1, 5000) AS col1);
+CREATE INDEX test2_col1_idx ON test2(col1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 0, 1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, -1);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 0);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 1, 2);
+SELECT * FROM bt_multi_page_stats('test2_col1_idx', 2, 6);
+DROP TABLE test2;
+
 SELECT * FROM bt_page_items('test1_a_idx', -1);
 SELECT * FROM bt_page_items('test1_a_idx', 0);
 SELECT * FROM bt_page_items('test1_a_idx', 1);

I wrote:
> 3. I think it's highly likely that the new test case is not portable.
> In particular a machine with MAXALIGN 4 would be likely to put a
> different number of tuples per page, or do the page split differently
> so that the page with fewer index tuples isn't page 3.  Unfortunately
> I don't seem to have a working setup like that right at the moment
> to verify; but I'd counsel trying this inside a VM or something to
> see if it's actually likely to survive on the buildfarm.

I spun up a 32-bit VM, since that had been on my to-do list anyway,
and it looks like I was right:

diff -U3 /usr/home/tgl/pgsql/contrib/pageinspect/expected/btree.out
/usr/home/tgl/pgsql/contrib/pageinspect/results/btree.out
--- /usr/home/tgl/pgsql/contrib/pageinspect/expected/btree.out  2022-09-12 15:15:40.432135000 -0400
+++ /usr/home/tgl/pgsql/contrib/pageinspect/results/btree.out   2022-09-12 15:15:54.481549000 -0400
@@ -49,11 +49,11 @@
 -[ RECORD 1 ]-+-----
 blkno         | 1
 type          | l
-live_items    | 367
+live_items    | 458
 dead_items    | 0
-avg_item_size | 16
+avg_item_size | 12
 page_size     | 8192
-free_size     | 808
+free_size     | 820
 btpo_prev     | 0
 btpo_next     | 2
 btpo_level    | 0
@@ -61,11 +61,11 @@
... etc etc ...

            regards, tom lane

On Mon, Sep 12, 2022 at 03:18:59PM -0400, Tom Lane wrote:
> I spun up a 32-bit VM, since that had been on my to-do list anyway,
> and it looks like I was right:

This feedback has not been addressed and the thread is idle four
weeks, so I have marked this CF entry as RwF.  Please feel free to
resubmit once a new version of the patch is available.
--
Michael

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       tested, passed
Spec compliant:           not tested
Documentation:            not tested

i've tested and verified the documentation.

Hi,

On 2022-11-25 02:45:01 +0500, Hamid Akhtar wrote:
> Rebasing the patch to the tip of the master branch.

This doesn't pass tests on cfbot. Looks like possibly some files are missing?

https://api.cirrus-ci.com/v1/artifact/task/4916614353649664/testrun/build/testrun/pageinspect/regress/regression.diffs

diff -U3 /tmp/cirrus-ci-build/contrib/pageinspect/expected/page.out
/tmp/cirrus-ci-build/build/testrun/pageinspect/regress/results/page.out
--- /tmp/cirrus-ci-build/contrib/pageinspect/expected/page.out    2022-12-06 20:07:47.691479000 +0000
+++ /tmp/cirrus-ci-build/build/testrun/pageinspect/regress/results/page.out    2022-12-06 20:11:42.955606000 +0000
@@ -1,4 +1,5 @@
 CREATE EXTENSION pageinspect;
+ERROR:  extension "pageinspect" has no installation script nor update path for version "1.12"
 -- Use a temp table so that effects of VACUUM are predictable
 CREATE TEMP TABLE test1 (a int, b int);
 INSERT INTO test1 VALUES (16777217, 131584);
@@ -6,236 +7,203 @@

Greetings,

Andres Freund

On 2022-Dec-06, Andres Freund wrote:

> Hi,
> 
> On 2022-11-25 02:45:01 +0500, Hamid Akhtar wrote:
> > Rebasing the patch to the tip of the master branch.
> 
> This doesn't pass tests on cfbot. Looks like possibly some files are missing?

The .sql file is there all right, but meson.build is not altered to be
aware of it.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/

The following review has been posted through the commitfest application:
make installcheck-world:  tested, passed
Implements feature:       tested, passed
Spec compliant:           tested, passed
Documentation:            not tested

Looks good to me

The new status of this patch is: Ready for Committer

Hamid Akhtar <hamid.akhtar@percona.com> writes:
> I wasn't aware of the meson.build file. Attached is the latest version of
> the patch that contains the updated meson.build.

Pushed with minor corrections, plus one major one: you missed the
point of aeaaf520f, that pageinspect functions that touch relations
need to be parallel-restricted not parallel-safe.

            regards, tom lane