On Thu, Oct 29, 2020 at 10:59:52AM +0900, Michael Paquier wrote:
> REINDEX CONCURRENTLY is by design wanted to provide an experience
> transparent to the user similar to what a plain REINDEX would do, at
> least that's the idea behind it, so..  This qualifies as a bug to me,
> in spirit.

And in spirit, it is possible to address this issue with the patch
attached which copies the set of stats from the old to the new index.
For a non-concurrent REINDEX, this does not happen because we keep the
same base relation, while we replace completely the relation with a
concurrent operation.  We have a RemoveStatistics() in heap.c, but I
did not really see the point to invent a copy flavor for this
particular case.  Perhaps others have an opinion on that?
--
Michael
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 0974f3e23a..3820a03fb6 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -49,6 +49,7 @@
 #include "catalog/pg_inherits.h"
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_operator.h"
+#include "catalog/pg_statistic.h"
 #include "catalog/pg_tablespace.h"
 #include "catalog/pg_trigger.h"
 #include "catalog/pg_type.h"
@@ -1711,6 +1712,44 @@ index_concurrently_swap(Oid newIndexId, Oid oldIndexId, const char *oldName)
 		}
 	}
 
+	/*
+	 * Copy over any data of pg_statistic from the old index to the new one.
+	 */
+	{
+		HeapTuple   tup;
+		SysScanDesc scan;
+		ScanKeyData key[1];
+		Relation	statrel;
+
+		statrel = table_open(StatisticRelationId, RowExclusiveLock);
+		ScanKeyInit(&key[0],
+					Anum_pg_statistic_starelid,
+					BTEqualStrategyNumber, F_OIDEQ,
+					ObjectIdGetDatum(oldIndexId));
+
+		scan = systable_beginscan(statrel, StatisticRelidAttnumInhIndexId,
+								  true, NULL, 1, key);
+
+		while (HeapTupleIsValid((tup = systable_getnext(scan))))
+		{
+			Form_pg_statistic statform;
+
+			/* make a modifiable copy */
+			tup = heap_copytuple(tup);
+			statform = (Form_pg_statistic) GETSTRUCT(tup);
+
+			/* update the copy of the tuple and insert it */
+			statform->starelid = newIndexId;
+			CatalogTupleInsert(statrel, tup);
+
+			heap_freetuple(tup);
+		}
+
+		systable_endscan(scan);
+
+		table_close(statrel, RowExclusiveLock);
+	}
+
 	/* Close relations */
 	table_close(pg_class, RowExclusiveLock);
 	table_close(pg_index, RowExclusiveLock);
diff --git a/src/test/regress/expected/create_index.out b/src/test/regress/expected/create_index.out
index 6ace7662ee..012c1eb067 100644
--- a/src/test/regress/expected/create_index.out
+++ b/src/test/regress/expected/create_index.out
@@ -2551,6 +2551,17 @@ CREATE UNIQUE INDEX concur_exprs_index_pred ON concur_exprs_tab (c1)
 CREATE UNIQUE INDEX concur_exprs_index_pred_2
   ON concur_exprs_tab ((1 / c1))
   WHERE ('-H') >= (c2::TEXT) COLLATE "C";
+ANALYZE concur_exprs_tab;
+SELECT starelid::regclass, count(*) FROM pg_statistic WHERE starelid IN (
+  'concur_exprs_index_expr'::regclass,
+  'concur_exprs_index_pred'::regclass,
+  'concur_exprs_index_pred_2'::regclass)
+  GROUP BY starelid ORDER BY starelid::regclass::text;
+        starelid         | count 
+-------------------------+-------
+ concur_exprs_index_expr |     1
+(1 row)
+
 SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
                                                 pg_get_indexdef                                                
 ---------------------------------------------------------------------------------------------------------------
@@ -2608,6 +2619,17 @@ SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
  CREATE UNIQUE INDEX concur_exprs_index_pred_2 ON public.concur_exprs_tab USING btree (((1 / c1))) WHERE ('-H'::text >= (c2 COLLATE "C"))
 (1 row)
 
+-- Statistics should remain intact.
+SELECT starelid::regclass, count(*) FROM pg_statistic WHERE starelid IN (
+  'concur_exprs_index_expr'::regclass,
+  'concur_exprs_index_pred'::regclass,
+  'concur_exprs_index_pred_2'::regclass)
+  GROUP BY starelid ORDER BY starelid::regclass::text;
+        starelid         | count 
+-------------------------+-------
+ concur_exprs_index_expr |     1
+(1 row)
+
 DROP TABLE concur_exprs_tab;
 -- Temporary tables and on-commit actions, where CONCURRENTLY is ignored.
 -- ON COMMIT PRESERVE ROWS, the default.
diff --git a/src/test/regress/sql/create_index.sql b/src/test/regress/sql/create_index.sql
index 37f7259da9..4e45b18613 100644
--- a/src/test/regress/sql/create_index.sql
+++ b/src/test/regress/sql/create_index.sql
@@ -1079,6 +1079,12 @@ CREATE UNIQUE INDEX concur_exprs_index_pred ON concur_exprs_tab (c1)
 CREATE UNIQUE INDEX concur_exprs_index_pred_2
   ON concur_exprs_tab ((1 / c1))
   WHERE ('-H') >= (c2::TEXT) COLLATE "C";
+ANALYZE concur_exprs_tab;
+SELECT starelid::regclass, count(*) FROM pg_statistic WHERE starelid IN (
+  'concur_exprs_index_expr'::regclass,
+  'concur_exprs_index_pred'::regclass,
+  'concur_exprs_index_pred_2'::regclass)
+  GROUP BY starelid ORDER BY starelid::regclass::text;
 SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
 SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
 SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
@@ -1091,6 +1097,12 @@ ALTER TABLE concur_exprs_tab ALTER c2 TYPE TEXT;
 SELECT pg_get_indexdef('concur_exprs_index_expr'::regclass);
 SELECT pg_get_indexdef('concur_exprs_index_pred'::regclass);
 SELECT pg_get_indexdef('concur_exprs_index_pred_2'::regclass);
+-- Statistics should remain intact.
+SELECT starelid::regclass, count(*) FROM pg_statistic WHERE starelid IN (
+  'concur_exprs_index_expr'::regclass,
+  'concur_exprs_index_pred'::regclass,
+  'concur_exprs_index_pred_2'::regclass)
+  GROUP BY starelid ORDER BY starelid::regclass::text;
 DROP TABLE concur_exprs_tab;
 
 -- Temporary tables and on-commit actions, where CONCURRENTLY is ignored.

Attachment: signature.asc
Description: PGP signature

Reply via email to