Feedback-ID: ie3de48e3:Fastmail
Date: Thu, 28 Aug 2025 23:33:42 +0200
From: =?utf-8?Q?=C3=81lvaro?= Herrera <alvherre@kurilemu.de>
To: jian he <jian.universality@gmail.com>
Cc: PostgreSQL-development <pgsql-hackers@postgresql.org>,
	Kirill Reshke <reshkekirill@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: misleading error message in ProcessUtilitySlow T_CreateStatsStmt
Message-ID: <202508282133.uwntzsze7cdl@alvherre.pgsql>
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On 2025-Aug-21, jian he wrote:

>             case T_CreateStatsStmt:
>                 {
>                     Oid            relid;
>                     CreateStatsStmt *stmt = (CreateStatsStmt *) parsetree;
>                     RangeVar   *rel = (RangeVar *) linitial(stmt->relations);
> 
>                     if (!IsA(rel, RangeVar))
>                         ereport(ERROR,
>                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>                                  errmsg("only a single relation is
> allowed in CREATE STATISTICS")));
>                     relid = RangeVarGetRelid(rel,
> ShareUpdateExclusiveLock, false);
>                     /* Run parse analysis ... */
>                     stmt = transformStatsStmt(relid, stmt, queryString);
>                     address = CreateStatistics(stmt);
>                 }

Yeah, I think there's room to argue that this ereport() is just wrongly
copy-and-pasted from other nearby errors, and that it should have
completely different wording.  BTW another way to cause this is

CREATE STATISTICS alt_stat2 ON a, b FROM xmltable('foo' passing 'bar' columns a text);

I propose to use this report:

ERROR:  cannot create statistics on specified relation
DETAIL:  CREATE STATISTICS only supports tables, materialized views, foreign tables, and partitioned tables.

(Not sold on saying just "tables" vs. "regular tables" or "plain tables";
thoughts?)

While looking at this whole thing, I noticed that this code is somewhat
bogus in a different way: we're resolving the relation name twice, both
here in ProcessUtilitySlow() (to pass to transformStatsStmt), and later
again inside CreateStatistics().  It's really strange that we decided
not to pass the relation Oids as a list argument to CreateStatistics.  I
suggest to change that as the first attached patch.

Now, such a change would be appropriate only for branch master; it seems too
invasive for stable ones.  For them I propose we only change the error message,
as in the other attachment.

We should add a couple of test cases for this particular error message
also.  It's bad that these changes don't break any tests.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Once again, thank you and all of the developers for your hard work on
PostgreSQL.  This is by far the most pleasant management experience of
any database I've worked on."                             (Dan Harris)
http://archives.postgresql.org/pgsql-performance/2006-04/msg00247.php

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	filename="0001-rewrite-ProcessUtilitySlow-code-for-CreateStatsStmt.patch"

From bebffcaa22a047c61b0fa588db56db60e59dc9ef Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Herrera?= <alvherre@kurilemu.de>
Date: Thu, 28 Aug 2025 19:49:14 +0200
Subject: [PATCH] rewrite ProcessUtilitySlow code for CreateStatsStmt

---
 src/backend/commands/statscmds.c   | 26 +++++-----------
 src/backend/commands/tablecmds.c   |  4 +--
 src/backend/parser/parse_utilcmd.c | 13 +++++---
 src/backend/tcop/utility.c         | 48 +++++++++++++++++-------------
 src/include/commands/defrem.h      |  2 +-
 src/include/parser/parse_utilcmd.h |  2 +-
 6 files changed, 49 insertions(+), 46 deletions(-)

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index e24d540cd45..07b2b5bfef3 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -59,7 +59,7 @@ compare_int16(const void *a, const void *b)
  *		CREATE STATISTICS
  */
 ObjectAddress
-CreateStatistics(CreateStatsStmt *stmt)
+CreateStatistics(CreateStatsStmt *stmt, List *relids)
 {
 	int16		attnums[STATS_MAX_DIMENSIONS];
 	int			nattnums = 0;
@@ -92,28 +92,18 @@ CreateStatistics(CreateStatsStmt *stmt)
 	ListCell   *cell;
 	ListCell   *cell2;
 
-	Assert(IsA(stmt, CreateStatsStmt));
-
 	/*
 	 * Examine the FROM clause.  Currently, we only allow it to be a single
 	 * simple table, but later we'll probably allow multiple tables and JOIN
-	 * syntax.  The grammar is already prepared for that, so we have to check
-	 * here that what we got is what we can support.
+	 * syntax.  Parse analysis checked the list length already, so this is
+	 * just defense-in-depth.
 	 */
-	if (list_length(stmt->relations) != 1)
-		ereport(ERROR,
-				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-				 errmsg("only a single relation is allowed in CREATE STATISTICS")));
+	Assert(list_length(stmt->relations) == list_length(relids));
+	if (list_length(relids) != 1)
+		elog(ERROR, "only a single relation is allowed in CREATE STATISTICS");
 
-	foreach(cell, stmt->relations)
+	foreach_oid(relid, relids)
 	{
-		Node	   *rln = (Node *) lfirst(cell);
-
-		if (!IsA(rln, RangeVar))
-			ereport(ERROR,
-					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-					 errmsg("only a single relation is allowed in CREATE STATISTICS")));
-
 		/*
 		 * CREATE STATISTICS will influence future execution plans but does
 		 * not interfere with currently executing plans.  So it should be
@@ -121,7 +111,7 @@ CreateStatistics(CreateStatsStmt *stmt)
 		 * conflicting with ANALYZE and other DDL that sets statistical
 		 * information, but not with normal queries.
 		 */
-		rel = relation_openrv((RangeVar *) rln, ShareUpdateExclusiveLock);
+		rel = relation_open(relid, ShareUpdateExclusiveLock);
 
 		/* Restrict to allowed relation types */
 		if (rel->rd_rel->relkind != RELKIND_RELATION &&
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 082a3575d62..1779bae80cb 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9654,7 +9654,7 @@ ATExecAddStatistics(AlteredTableInfo *tab, Relation rel,
 	/* The CreateStatsStmt has already been through transformStatsStmt */
 	Assert(stmt->transformed);
 
-	address = CreateStatistics(stmt);
+	address = CreateStatistics(stmt, list_make1_oid(RelationGetRelid(rel)));
 
 	return address;
 }
@@ -15631,7 +15631,7 @@ ATPostAlterTypeParse(Oid oldId, Oid oldRelId, Oid refRelId, char *cmd,
 		}
 		else if (IsA(stmt, CreateStatsStmt))
 			querytree_list = lappend(querytree_list,
-									 transformStatsStmt(oldRelId,
+									 transformStatsStmt(list_make1_oid(oldRelId),
 														(CreateStatsStmt *) stmt,
 														cmd));
 		else
diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index afcf54169c3..587e2ef439c 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -3138,11 +3138,11 @@ transformIndexStmt(Oid relid, IndexStmt *stmt, const char *queryString)
  * transformStatsStmt - parse analysis for CREATE STATISTICS
  *
  * To avoid race conditions, it's important that this function relies only on
- * the passed-in relid (and not on stmt->relation) to determine the target
- * relation.
+ * the passed-in relids list (and not on stmt->relations) to determine the
+ * target relation.
  */
 CreateStatsStmt *
-transformStatsStmt(Oid relid, CreateStatsStmt *stmt, const char *queryString)
+transformStatsStmt(List *relids, CreateStatsStmt *stmt, const char *queryString)
 {
 	ParseState *pstate;
 	ParseNamespaceItem *nsitem;
@@ -3153,6 +3153,11 @@ transformStatsStmt(Oid relid, CreateStatsStmt *stmt, const char *queryString)
 	if (stmt->transformed)
 		return stmt;
 
+	if (list_length(relids) != 1)
+		ereport(ERROR,
+				errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				errmsg("only a single relation is allowed in CREATE STATISTICS"));
+
 	/* Set up pstate */
 	pstate = make_parsestate(NULL);
 	pstate->p_sourcetext = queryString;
@@ -3162,7 +3167,7 @@ transformStatsStmt(Oid relid, CreateStatsStmt *stmt, const char *queryString)
 	 * to its fields without qualification.  Caller is responsible for locking
 	 * relation, but we still need to open it.
 	 */
-	rel = relation_open(relid, NoLock);
+	rel = relation_open(linitial_oid(relids), NoLock);
 	nsitem = addRangeTableEntryForRelation(pstate, rel,
 										   AccessShareLock,
 										   NULL, false, true);
diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 4f4191b0ea6..e09da051310 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1867,32 +1867,40 @@ ProcessUtilitySlow(ParseState *pstate,
 
 			case T_CreateStatsStmt:
 				{
-					Oid			relid;
 					CreateStatsStmt *stmt = (CreateStatsStmt *) parsetree;
-					RangeVar   *rel = (RangeVar *) linitial(stmt->relations);
+					List	   *relids = NIL;
+					ListCell   *cell;
 
-					if (!IsA(rel, RangeVar))
-						ereport(ERROR,
-								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-								 errmsg("only a single relation is allowed in CREATE STATISTICS")));
+					foreach(cell, stmt->relations)
+					{
+						Oid			relid;
 
-					/*
-					 * CREATE STATISTICS will influence future execution plans
-					 * but does not interfere with currently executing plans.
-					 * So it should be enough to take ShareUpdateExclusiveLock
-					 * on relation, conflicting with ANALYZE and other DDL
-					 * that sets statistical information, but not with normal
-					 * queries.
-					 *
-					 * XXX RangeVarCallbackOwnsRelation not needed here, to
-					 * keep the same behavior as before.
-					 */
-					relid = RangeVarGetRelid(rel, ShareUpdateExclusiveLock, false);
+						if (!IsA(lfirst(cell), RangeVar))
+							ereport(ERROR,
+									errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+									errmsg("cannot create statistics on specified relation"),
+									errdetail("CREATE STATISTICS only supports tables, materialized views, foreign tables, and partitioned tables."));
 
+						/*
+						 * CREATE STATISTICS will influence future execution
+						 * plans but does not interfere with currently
+						 * executing plans.  So it should be enough to take
+						 * ShareUpdateExclusiveLock on relation, conflicting
+						 * with ANALYZE and other DDL that sets statistical
+						 * information, but not with normal queries.
+						 *
+						 * XXX RangeVarCallbackOwnsRelation not needed here,
+						 * to keep the same behavior as before.
+						 */
+						relid = RangeVarGetRelid(castNode(RangeVar, lfirst(cell)),
+												 ShareUpdateExclusiveLock, false);
+						relids = lappend_oid(relids, relid);
+					}
 					/* Run parse analysis ... */
-					stmt = transformStatsStmt(relid, stmt, queryString);
+					stmt = transformStatsStmt(relids, stmt, queryString);
 
-					address = CreateStatistics(stmt);
+					/* ... and execute the command */
+					address = CreateStatistics(stmt, relids);
 				}
 				break;
 
diff --git a/src/include/commands/defrem.h b/src/include/commands/defrem.h
index dd22b5efdfd..7b8cb40cd83 100644
--- a/src/include/commands/defrem.h
+++ b/src/include/commands/defrem.h
@@ -85,7 +85,7 @@ extern void RemoveOperatorById(Oid operOid);
 extern ObjectAddress AlterOperator(AlterOperatorStmt *stmt);
 
 /* commands/statscmds.c */
-extern ObjectAddress CreateStatistics(CreateStatsStmt *stmt);
+extern ObjectAddress CreateStatistics(CreateStatsStmt *stmt, List *relids);
 extern ObjectAddress AlterStatistics(AlterStatsStmt *stmt);
 extern void RemoveStatisticsById(Oid statsOid);
 extern void RemoveStatisticsDataById(Oid statsOid, bool inh);
diff --git a/src/include/parser/parse_utilcmd.h b/src/include/parser/parse_utilcmd.h
index 9f2b58de797..28165eb1198 100644
--- a/src/include/parser/parse_utilcmd.h
+++ b/src/include/parser/parse_utilcmd.h
@@ -26,7 +26,7 @@ extern AlterTableStmt *transformAlterTableStmt(Oid relid, AlterTableStmt *stmt,
 											   List **afterStmts);
 extern IndexStmt *transformIndexStmt(Oid relid, IndexStmt *stmt,
 									 const char *queryString);
-extern CreateStatsStmt *transformStatsStmt(Oid relid, CreateStatsStmt *stmt,
+extern CreateStatsStmt *transformStatsStmt(List *relids, CreateStatsStmt *stmt,
 										   const char *queryString);
 extern void transformRuleStmt(RuleStmt *stmt, const char *queryString,
 							  List **actions, Node **whereClause);
-- 
2.39.5


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Content-Type: text/x-diff; charset=utf-8
Content-Disposition: attachment;
	filename="0001-CREATE-STATISTICS-Fix-error-message.patch"

From 0ad9908e2ad2762445807136784b18777fac4c87 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=81lvaro=20Herrera?= <alvherre@kurilemu.de>
Date: Thu, 28 Aug 2025 19:53:44 +0200
Subject: [PATCH] CREATE STATISTICS: Fix error message

---
 src/backend/tcop/utility.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/backend/tcop/utility.c b/src/backend/tcop/utility.c
index 25fe3d58016..7f5076d2c1a 100644
--- a/src/backend/tcop/utility.c
+++ b/src/backend/tcop/utility.c
@@ -1883,7 +1883,8 @@ ProcessUtilitySlow(ParseState *pstate,
 					if (!IsA(rel, RangeVar))
 						ereport(ERROR,
 								(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-								 errmsg("only a single relation is allowed in CREATE STATISTICS")));
+								 errmsg("cannot create statistics on specified relation"),
+								 errdetail("CREATE STATISTICS only supports tables, materialized views, foreign tables, and partitioned tables.")));
 
 					/*
 					 * CREATE STATISTICS will influence future execution plans
-- 
2.39.5


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