Date: Fri, 3 Apr 2026 10:44:53 +0900
From: Yugo Nagata <nagata@sraoss.co.jp>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: John Naylor <johncnaylorls@gmail.com>, Michael Paquier
 <michael@paquier.xyz>, Pgsql Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Adjust error message for CREATE STATISTICS to account for
 expressions
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On Wed, 1 Apr 2026 17:19:16 +0100
Dean Rasheed <dean.a.rasheed@gmail.com> wrote:

> On Tue, 31 Mar 2026 at 15:47, Yugo Nagata <nagata@sraoss.co.jp> wrote:
> >
> > Yes, that sounds good to me.
> >
> > In particular, the following suggestion from Dean Rasheed seems like a
> > good approach:
> >
> > > Error: cannot create extended statistics on a single column
> > > Detail: Univariate statistics are already built for each individual
> > > table column
> 
> I've pushed that change as part of the patch to support extended
> statistics on virtual generated columns [1], since I felt that patch
> already needed to change that error message.

Thank you for handling this.
 
> I didn't look more widely at other error messages in that file might
> benefit from having separate errdetail text.

I’ve attached a patch that also updates other error messages to move
their reason parts into errdetail.

Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

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diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index eea45106a3f..b354723be44 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -280,8 +280,10 @@ CreateStatistics(CreateStatsStmt *stmt, bool check_rights)
 				if (type->lt_opr == InvalidOid)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("column \"%s\" cannot be used in multivariate statistics because its type %s has no default btree operator class",
-									attname, format_type_be(attForm->atttypid))));
+							 errmsg("cannot create multivariate statistics on column \"%s\"",
+									attname),
+							 errdetail("The type %s has no default btree operator class.",
+									   format_type_be(attForm->atttypid))));
 			}
 
 			/* Treat virtual generated columns as expressions */
@@ -325,8 +327,10 @@ CreateStatistics(CreateStatsStmt *stmt, bool check_rights)
 				if (type->lt_opr == InvalidOid)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("column \"%s\" cannot be used in multivariate statistics because its type %s has no default btree operator class",
-									get_attname(relid, var->varattno, false), format_type_be(var->vartype))));
+							 errmsg("cannot create multivariate statistics on column \"%s\"",
+									get_attname(relid, var->varattno, false)),
+							 errdetail("The type %s has no default btree operator class.",
+									   format_type_be(var->vartype))));
 			}
 
 			/* Treat virtual generated columns as expressions */
@@ -375,8 +379,9 @@ CreateStatistics(CreateStatsStmt *stmt, bool check_rights)
 				if (type->lt_opr == InvalidOid)
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-							 errmsg("expression cannot be used in multivariate statistics because its type %s has no default btree operator class",
-									format_type_be(atttype))));
+							 errmsg("cannot create multivariate statistics on this expression"),
+							 errdetail("The type %s has no default btree operator class.",
+									   format_type_be(atttype))));
 			}
 
 			stxexprs = lappend(stxexprs, expr);
diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out
index c6ba2479413..37070c1a896 100644
--- a/src/test/regress/expected/stats_ext.out
+++ b/src/test/regress/expected/stats_ext.out
@@ -99,7 +99,8 @@ CREATE STATISTICS tst (ndistinct) ON (y + z) FROM ext_stats_test;
 ERROR:  cannot specify statistics kinds when building univariate statistics
 -- multivariate statistics without a less-than operator not supported
 CREATE STATISTICS tst (ndistinct) ON x, w from ext_stats_test;
-ERROR:  column "w" cannot be used in multivariate statistics because its type xid has no default btree operator class
+ERROR:  cannot create multivariate statistics on column "w"
+DETAIL:  The type xid has no default btree operator class.
 DROP TABLE ext_stats_test;
 -- Ensure stats are dropped sanely, and test IF NOT EXISTS while at it
 CREATE TABLE ab1 (a INTEGER, b INTEGER, c INTEGER);

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