pgstat: add pgstat_copy_relation_stats().

Until now index_concurrently_swap() directly modified pgstat internal
datastructures. That will break with the introduction of shared memory
statistics and seems off architecturally.

This is done separately from the - quite large - shared memory statistics
patch to make review easier.

Author: Andres Freund <andres@anarazel.de>
Author: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Reviewed-By: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220303021600.hs34ghqcw6zcokdh@alap3.anarazel.de

diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 55800c947867891f360fc665eecce160c6a77e0b..fd389c28d836d36700eff13a646773e8174fa0df 100644 (file)
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -1734,30 +1734,8 @@ index_concurrently_swap(Oid newIndexId, Oid oldIndexId, const char *oldName)
        changeDependenciesOf(RelationRelationId, oldIndexId, newIndexId);
        changeDependenciesOn(RelationRelationId, oldIndexId, newIndexId);
 
-       /*
-        * Copy over statistics from old to new index
-        */
-       {
-               PgStat_StatTabEntry *tabentry;
-
-               tabentry = pgstat_fetch_stat_tabentry(oldIndexId);
-               if (tabentry)
-               {
-                       if (pgstat_relation_should_count(newClassRel))
-                       {
-                               newClassRel->pgstat_info->t_counts.t_numscans = tabentry->numscans;
-                               newClassRel->pgstat_info->t_counts.t_tuples_returned = tabentry->tuples_returned;
-                               newClassRel->pgstat_info->t_counts.t_tuples_fetched = tabentry->tuples_fetched;
-                               newClassRel->pgstat_info->t_counts.t_blocks_fetched = tabentry->blocks_fetched;
-                               newClassRel->pgstat_info->t_counts.t_blocks_hit = tabentry->blocks_hit;
-
-                               /*
-                                * The data will be sent by the next pgstat_report_stat()
-                                * call.
-                                */
-                       }
-               }
-       }
+       /* copy over statistics from old to new index */
+       pgstat_copy_relation_stats(newClassRel, oldClassRel);
 
        /* Copy data of pg_statistic from the old index to the new one */
        CopyStatistics(oldIndexId, newIndexId);

diff --git a/src/backend/utils/activity/pgstat_relation.c b/src/backend/utils/activity/pgstat_relation.c
index a78b8d2450f77a234c96ae491761cd5c80fbca82..4f97d2f1d9c41a7c1ce1ebe50ff8651a338763ff 100644 (file)
--- a/src/backend/utils/activity/pgstat_relation.c
+++ b/src/backend/utils/activity/pgstat_relation.c
@@ -95,6 +95,38 @@ bool         have_relation_stats;
 static HTAB *pgStatTabHash = NULL;
 
 
+/*
+ * Copy stats between relations. This is used for things like REINDEX
+ * CONCURRENTLY.
+ */
+void
+pgstat_copy_relation_stats(Relation dst, Relation src)
+{
+       PgStat_StatTabEntry *srcstats;
+
+       srcstats = pgstat_fetch_stat_tabentry(RelationGetRelid(src));
+
+       if (!srcstats)
+               return;
+
+       if (pgstat_relation_should_count(dst))
+       {
+               /*
+                * XXX: temporarily this does not actually quite do what the name
+                * says, and just copy index related fields. A subsequent commit will
+                * do more.
+                */
+
+               dst->pgstat_info->t_counts.t_numscans = srcstats->numscans;
+               dst->pgstat_info->t_counts.t_tuples_returned = srcstats->tuples_returned;
+               dst->pgstat_info->t_counts.t_tuples_fetched = srcstats->tuples_fetched;
+               dst->pgstat_info->t_counts.t_blocks_fetched = srcstats->blocks_fetched;
+               dst->pgstat_info->t_counts.t_blocks_hit = srcstats->blocks_hit;
+
+               /* the data will be sent by the next pgstat_report_stat() call */
+       }
+}
+
 /*
  * Initialize a relcache entry to count access statistics.
  * Called whenever a relation is opened.

diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index aaab2f973b3ef712224cc75eadbd78a88c6943f5..ed141f2d2fd7221164a40146103e4944d7d4a83d 100644 (file)
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -1053,6 +1053,8 @@ extern PgStat_BackendFunctionEntry *find_funcstat_entry(Oid func_id);
  * Functions in pgstat_relation.c
  */
 
+extern void pgstat_copy_relation_stats(Relation dstrel, Relation srcrel);
+
 extern void pgstat_relation_init(Relation rel);
 
 extern void pgstat_report_vacuum(Oid tableoid, bool shared,