From 339ce77cac927e463324276a6691962c1de852d6 Mon Sep 17 00:00:00 2001 From: Nikolay Samokhvalov Date: Tue, 24 Mar 2026 03:26:24 +0000 Subject: [PATCH] Doc: clarify that pg_upgrade statistics transfer works cross-version. Clarify in pgupgrade.sgml that optimizer statistics transfer works regardless of the old cluster's major version. The new cluster's pg_dump reads statistics from standard catalog views (pg_class and pg_stats) in the old cluster, which exist in all supported PostgreSQL versions. The restore functions (pg_restore_relation_stats and pg_restore_attribute_stats) only need to exist on the target cluster. Tested with PG14->PG18 and PG16->PG18. --- doc/src/sgml/ref/pgupgrade.sgml | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/ref/pgupgrade.sgml b/doc/src/sgml/ref/pgupgrade.sgml index 38ca09b..d552907 100644 --- a/doc/src/sgml/ref/pgupgrade.sgml +++ b/doc/src/sgml/ref/pgupgrade.sgml @@ -833,10 +833,15 @@ psql --username=postgres --file=script.sql postgres Unless the option is specified, pg_upgrade will transfer most optimizer statistics - from the old cluster to the new cluster. This does not transfer - all statistics, such as those created explicitly with - , custom statistics added by - an extension, or statistics collected by the cumulative statistics system. + from the old cluster to the new cluster. This works regardless of + the old cluster's major version, because the new cluster's + pg_dump reads statistics from standard catalog views + (pg_class and pg_stats) + that exist in all supported PostgreSQL + versions. However, some statistics are not transferred: those created + with , custom statistics added by + an extension, and statistics collected by the cumulative statistics + system. -- 2.43.0