pgstat: fix small bug in pgstat_drop_relation().

Just after committing 5891c7a8ed8, a test running with debug_discard_caches=1
failed locally...

pgstat_drop_relation() neither checked pgstat_should_count_relation() nor
called pgstat_prep_relation_pending(). With debug_discard_caches=1
rel->pgstat_info wasn't set up, leading pg_stat_get_xact_tuples_inserted()
spuriously still returning > 0 while in the transaction dropping the table.

diff --git a/src/backend/utils/activity/pgstat_relation.c b/src/backend/utils/activity/pgstat_relation.c
index bec190c589753883d96d84cd2591dc02ed85849f..a846d9ffb652b5586d3b784a083ce2d9369b7299 100644 (file)
--- a/src/backend/utils/activity/pgstat_relation.c
+++ b/src/backend/utils/activity/pgstat_relation.c
@@ -180,18 +180,21 @@ void
 pgstat_drop_relation(Relation rel)
 {
    int         nest_level = GetCurrentTransactionNestLevel();
-   PgStat_TableStatus *pgstat_info = rel->pgstat_info;
+   PgStat_TableStatus *pgstat_info;
 
    pgstat_drop_transactional(PGSTAT_KIND_RELATION,
                              rel->rd_rel->relisshared ? InvalidOid : MyDatabaseId,
                              RelationGetRelid(rel));
 
+   if (!pgstat_should_count_relation(rel))
+       return;
+
    /*
     * Transactionally set counters to 0. That ensures that accesses to
     * pg_stat_xact_all_tables inside the transaction show 0.
     */
-   if (pgstat_info &&
-       pgstat_info->trans != NULL &&
+   pgstat_info = rel->pgstat_info;
+   if (pgstat_info->trans &&
        pgstat_info->trans->nest_level == nest_level)
    {
        save_truncdrop_counters(pgstat_info->trans, true);