Date: Tue, 17 Mar 2026 10:01:42 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Corey Huinker <corey.huinker@gmail.com>
Cc: Michael Paquier <michael@paquier.xyz>,
	Sami Imseih <samimseih@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Subject: Re: Add starelid, attnum to pg_stats and leverage this in pg_dump
Message-ID: <abls1l0aNZMRu33u@nathan>
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On Tue, Mar 17, 2026 at 09:26:57AM -0500, Nathan Bossart wrote:
> Committed the next patch in the series.  I'll have a rebased version of the
> last one ready to share soon.

As promised...

-- 
nathan

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	filename=v10-0001-pg_dump-Simplify-query-in-getAttributeStats.patch

From 3d2e9ac40c3695ba60d50c66112d48423734c641 Mon Sep 17 00:00:00 2001
From: Nathan Bossart <nathan@postgresql.org>
Date: Tue, 17 Mar 2026 09:35:32 -0500
Subject: [PATCH v10 1/1] pg_dump: Simplify query in getAttributeStats().

Presently, this query fetches information from pg_stats, which did
not return table OIDs until recent commit 3b88e50d6c.  Because of
this, we had to cart around arrays of schema and table names, and
we needed an extra filter clause to hopefully convince the planner
to use the correct index.  With the introduction of
pg_stats.tableid, we can instead just use an array of OIDs without
the extra filter clause hack.

Author: Corey Huinker <corey.huinker@gmail.com>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Discussion: https://postgr.es/m/CADkLM%3DcoCVy92QkVUUTLdo5eO2bMDtwMrzRn_8miAhX%2BuPaqXg%40mail.gmail.com
---
 src/bin/pg_dump/pg_dump.c | 65 +++++++++++++++++++++++++++++++--------
 src/bin/pg_dump/pg_dump.h |  1 +
 2 files changed, 54 insertions(+), 12 deletions(-)

diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 23af95027e6..ad09677c336 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -7227,6 +7227,7 @@ getRelationStatistics(Archive *fout, DumpableObject *rel, int32 relpages,
 		dobj->components |= DUMP_COMPONENT_STATISTICS;
 		dobj->name = pg_strdup(rel->name);
 		dobj->namespace = rel->namespace;
+		info->relid = rel->catId.oid;
 		info->relpages = relpages;
 		info->reltuples = pstrdup(reltuples);
 		info->relallvisible = relallvisible;
@@ -11122,6 +11123,7 @@ static PGresult *
 fetchAttributeStats(Archive *fout)
 {
 	ArchiveHandle *AH = (ArchiveHandle *) fout;
+	PQExpBuffer relids = createPQExpBuffer();
 	PQExpBuffer nspnames = createPQExpBuffer();
 	PQExpBuffer relnames = createPQExpBuffer();
 	int			count = 0;
@@ -11157,6 +11159,7 @@ fetchAttributeStats(Archive *fout)
 		restarted = true;
 	}
 
+	appendPQExpBufferChar(relids, '{');
 	appendPQExpBufferChar(nspnames, '{');
 	appendPQExpBufferChar(relnames, '{');
 
@@ -11168,15 +11171,28 @@ fetchAttributeStats(Archive *fout)
 	 */
 	for (; te != AH->toc && count < max_rels; te = te->next)
 	{
-		if ((te->reqs & REQ_STATS) != 0 &&
-			strcmp(te->desc, "STATISTICS DATA") == 0)
+		if ((te->reqs & REQ_STATS) == 0 ||
+			strcmp(te->desc, "STATISTICS DATA") != 0)
+			continue;
+
+		if (fout->remoteVersion >= 190000)
+		{
+			RelStatsInfo *rsinfo = (RelStatsInfo *) te->defnDumperArg;
+			char		relid[32];
+
+			sprintf(relid, "%u", rsinfo->relid);
+			appendPGArray(relids, relid);
+		}
+		else
 		{
 			appendPGArray(nspnames, te->namespace);
 			appendPGArray(relnames, te->tag);
-			count++;
 		}
+
+		count++;
 	}
 
+	appendPQExpBufferChar(relids, '}');
 	appendPQExpBufferChar(nspnames, '}');
 	appendPQExpBufferChar(relnames, '}');
 
@@ -11186,14 +11202,25 @@ fetchAttributeStats(Archive *fout)
 		PQExpBuffer query = createPQExpBuffer();
 
 		appendPQExpBufferStr(query, "EXECUTE getAttributeStats(");
-		appendStringLiteralAH(query, nspnames->data, fout);
-		appendPQExpBufferStr(query, "::pg_catalog.name[],");
-		appendStringLiteralAH(query, relnames->data, fout);
-		appendPQExpBufferStr(query, "::pg_catalog.name[])");
+
+		if (fout->remoteVersion >= 190000)
+		{
+			appendStringLiteralAH(query, relids->data, fout);
+			appendPQExpBufferStr(query, "::pg_catalog.oid[])");
+		}
+		else
+		{
+			appendStringLiteralAH(query, nspnames->data, fout);
+			appendPQExpBufferStr(query, "::pg_catalog.name[],");
+			appendStringLiteralAH(query, relnames->data, fout);
+			appendPQExpBufferStr(query, "::pg_catalog.name[])");
+		}
+
 		res = ExecuteSqlQuery(fout, query->data, PGRES_TUPLES_OK);
 		destroyPQExpBuffer(query);
 	}
 
+	destroyPQExpBuffer(relids);
 	destroyPQExpBuffer(nspnames);
 	destroyPQExpBuffer(relnames);
 	return res;
@@ -11254,8 +11281,14 @@ dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
 	query = createPQExpBuffer();
 	if (!fout->is_prepared[PREPQUERY_GETATTRIBUTESTATS])
 	{
+		if (fout->remoteVersion >= 190000)
+			appendPQExpBufferStr(query,
+								 "PREPARE getAttributeStats(pg_catalog.oid[]) AS\n");
+		else
+			appendPQExpBufferStr(query,
+								 "PREPARE getAttributeStats(pg_catalog.name[], pg_catalog.name[]) AS\n");
+
 		appendPQExpBufferStr(query,
-							 "PREPARE getAttributeStats(pg_catalog.name[], pg_catalog.name[]) AS\n"
 							 "SELECT s.schemaname, s.tablename, s.attname, s.inherited, "
 							 "s.null_frac, s.avg_width, s.n_distinct, "
 							 "s.most_common_vals, s.most_common_freqs, "
@@ -11277,17 +11310,25 @@ dumpRelationStats_dumper(Archive *fout, const void *userArg, const TocEntry *te)
 		/*
 		 * The results must be in the order of the relations supplied in the
 		 * parameters to ensure we remain in sync as we walk through the TOC.
-		 * The redundant filter clause on s.tablename = ANY(...) seems
-		 * sufficient to convince the planner to use
+		 *
+		 * For v9.4 through v18, the redundant filter clause on s.tablename =
+		 * ANY(...) seems sufficient to convince the planner to use
 		 * pg_class_relname_nsp_index, which avoids a full scan of pg_stats.
-		 * This may not work for all versions.
+		 * In newer versions, pg_stats returns the table OIDs, eliminating the
+		 * need for that hack.
 		 *
 		 * Our query for retrieving statistics for multiple relations uses
 		 * WITH ORDINALITY and multi-argument UNNEST(), both of which were
 		 * introduced in v9.4.  For older versions, we resort to gathering
 		 * statistics for a single relation at a time.
 		 */
-		if (fout->remoteVersion >= 90400)
+		if (fout->remoteVersion >= 190000)
+			appendPQExpBufferStr(query,
+								 "FROM pg_catalog.pg_stats s "
+								 "JOIN unnest($1) WITH ORDINALITY AS u (tableid, ord) "
+								 "ON s.tableid = u.tableid "
+								 "ORDER BY u.ord, s.attname, s.inherited");
+		else if (fout->remoteVersion >= 90400)
 			appendPQExpBufferStr(query,
 								 "FROM pg_catalog.pg_stats s "
 								 "JOIN unnest($1, $2) WITH ORDINALITY AS u (schemaname, tablename, ord) "
diff --git a/src/bin/pg_dump/pg_dump.h b/src/bin/pg_dump/pg_dump.h
index 1c11a79083f..2b9c01b2c0a 100644
--- a/src/bin/pg_dump/pg_dump.h
+++ b/src/bin/pg_dump/pg_dump.h
@@ -448,6 +448,7 @@ typedef struct _indexAttachInfo
 typedef struct _relStatsInfo
 {
 	DumpableObject dobj;
+	Oid			relid;
 	int32		relpages;
 	char	   *reltuples;
 	int32		relallvisible;
-- 
2.50.1 (Apple Git-155)


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