Keep stats up to date for partitioned tables

In the long-going saga for analyze on partitioned tables, one thing I
missed while reverting 0827e8af70f4 is the maintenance of analyze count
and last analyze time for partitioned tables.  This is a mostly trivial
change that enables users assess the need for invoking manual ANALYZE on
partitioned tables.

This patch, posted by Justin and modified a bit by me (Álvaro), can be
mostly traced back to Hosoya-san, though any problems introduced with
the scissors are mine.

Backpatch to 14, in line with 6f8127b73901.

Co-authored-by: Yuzuko Hosoya <yuzukohosoya@gmail.com>
Co-authored-by: Justin Pryzby <pryzby@telsasoft.com>
Co-authored-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reported-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20210816222810.GE10479@telsasoft.com

src/backend/commands/analyze.c

@@ -626,8 +626,8 @@ do_analyze_rel(Relation onerel, VacuumParams *params,
 								 PROGRESS_ANALYZE_PHASE_FINALIZE_ANALYZE);
 
 	/*
-	 * Update pages/tuples stats in pg_class, and report ANALYZE to the stats
+	 * Update pages/tuples stats in pg_class ... but not if we're doing
-	 * collector ... but not if we're doing inherited stats.
+	 * inherited stats.
 	 *
 	 * We assume that VACUUM hasn't set pg_class.reltuples already, even
 	 * during a VACUUM ANALYZE.  Although VACUUM often updates pg_class,
@@ -668,20 +668,33 @@ do_analyze_rel(Relation onerel, VacuumParams *params,
 								InvalidMultiXactId,
 								in_outer_xact);
 		}
-
+	}
+	else if (onerel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+	{
 		/*
-		 * Now report ANALYZE to the stats collector.
+		 * Partitioned tables don't have storage, so we don't set any fields
-		 *
+		 * in their pg_class entries except for reltuples and relhasindex.
-		 * We deliberately don't report to the stats collector when doing
-		 * inherited stats, because the stats collector only tracks per-table
-		 * stats.
-		 *
-		 * Reset the changes_since_analyze counter only if we analyzed all
-		 * columns; otherwise, there is still work for auto-analyze to do.
 		 */
+		vac_update_relstats(onerel, -1, totalrows,
+							0, hasindex, InvalidTransactionId,
+							InvalidMultiXactId,
+							in_outer_xact);
+	}
+
+	/*
+	 * Now report ANALYZE to the stats collector.  For regular tables, we do
+	 * it only if not doing inherited stats.  For partitioned tables, we only
+	 * do it for inherited stats. (We're never called for not-inherited stats
+	 * on partitioned tables anyway.)
+	 *
+	 * Reset the changes_since_analyze counter only if we analyzed all
+	 * columns; otherwise, there is still work for auto-analyze to do.
+	 */
+	if (!inh)
 		pgstat_report_analyze(onerel, totalrows, totaldeadrows,
 							  (va_cols == NIL));
-	}
+	else if (onerel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		pgstat_report_analyze(onerel, 0, 0, (va_cols == NIL));
 
 	/*
 	 * If this isn't part of VACUUM ANALYZE, let index AMs do cleanup.

src/backend/postmaster/pgstat.c

@@ -1618,8 +1618,11 @@ pgstat_report_analyze(Relation rel,
 	 * be double-counted after commit.  (This approach also ensures that the
 	 * collector ends up with the right numbers if we abort instead of
 	 * committing.)
+	 *
+	 * Waste no time on partitioned tables, though.
 	 */
-	if (rel->pgstat_info != NULL)
+	if (rel->pgstat_info != NULL &&
+		rel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
 	{
 		PgStat_TableXactStatus *trans;
 
@@ -1981,8 +1984,10 @@ pgstat_initstats(Relation rel)
 	Oid			rel_id = rel->rd_id;
 	char		relkind = rel->rd_rel->relkind;
 
-	/* We only count stats for things that have storage */
+	/*
-	if (!RELKIND_HAS_STORAGE(relkind))
+	 * We only count stats for relations with storage and partitioned tables
+	 */
+	if (!RELKIND_HAS_STORAGE(relkind) && relkind != RELKIND_PARTITIONED_TABLE)
 	{
 		rel->pgstat_info = NULL;
 		return;