Fix pg_statio_all_tables view for multiple TOAST indexes.

A TOAST table can normally have only one index, but there are corner
cases where it has more; for example, transiently during REINDEX
CONCURRENTLY.  In such a case, the pg_statio_all_tables view produced
multiple rows for the owning table, one per TOAST index.  Refactor the
view to avoid that, instead summing the stats across all the indexes,
as we do for regular table indexes.

While this has been wrong for a long time, back-patching seems unwise
due to the difficulty of putting a system view change into back
branches.

Andrei Zubkov, tweaked a bit by me

Discussion: https://postgr.es/m/acefef4189706971fc475f912c1afdab1c48d627.camel@moonset.ru

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 9ac8e9a2998b9b37de85837ff20e15a86e144975..9570a53e7bece01f43a381236f15ef838bf77077 100644 (file)
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -727,22 +727,31 @@ CREATE VIEW pg_statio_all_tables AS
             pg_stat_get_blocks_fetched(C.oid) -
                     pg_stat_get_blocks_hit(C.oid) AS heap_blks_read,
             pg_stat_get_blocks_hit(C.oid) AS heap_blks_hit,
-            sum(pg_stat_get_blocks_fetched(I.indexrelid) -
-                    pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_read,
-            sum(pg_stat_get_blocks_hit(I.indexrelid))::bigint AS idx_blks_hit,
+            I.idx_blks_read AS idx_blks_read,
+            I.idx_blks_hit AS idx_blks_hit,
             pg_stat_get_blocks_fetched(T.oid) -
                     pg_stat_get_blocks_hit(T.oid) AS toast_blks_read,
             pg_stat_get_blocks_hit(T.oid) AS toast_blks_hit,
-            pg_stat_get_blocks_fetched(X.indexrelid) -
-                    pg_stat_get_blocks_hit(X.indexrelid) AS tidx_blks_read,
-            pg_stat_get_blocks_hit(X.indexrelid) AS tidx_blks_hit
+            X.idx_blks_read AS tidx_blks_read,
+            X.idx_blks_hit AS tidx_blks_hit
     FROM pg_class C LEFT JOIN
-            pg_index I ON C.oid = I.indrelid LEFT JOIN
-            pg_class T ON C.reltoastrelid = T.oid LEFT JOIN
-            pg_index X ON T.oid = X.indrelid
+            pg_class T ON C.reltoastrelid = T.oid
             LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
-    WHERE C.relkind IN ('r', 't', 'm')
-    GROUP BY C.oid, N.nspname, C.relname, T.oid, X.indexrelid;
+            LEFT JOIN LATERAL (
+              SELECT sum(pg_stat_get_blocks_fetched(indexrelid) -
+                         pg_stat_get_blocks_hit(indexrelid))::bigint
+                     AS idx_blks_read,
+                     sum(pg_stat_get_blocks_hit(indexrelid))::bigint
+                     AS idx_blks_hit
+              FROM pg_index WHERE indrelid = C.oid ) I ON true
+            LEFT JOIN LATERAL (
+              SELECT sum(pg_stat_get_blocks_fetched(indexrelid) -
+                         pg_stat_get_blocks_hit(indexrelid))::bigint
+                     AS idx_blks_read,
+                     sum(pg_stat_get_blocks_hit(indexrelid))::bigint
+                     AS idx_blks_hit
+              FROM pg_index WHERE indrelid = T.oid ) X ON true
+    WHERE C.relkind IN ('r', 't', 'm');
 
 CREATE VIEW pg_statio_sys_tables AS
     SELECT * FROM pg_statio_all_tables

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index db9963db72764c292de6a627759cdb28df00aafe..a3a49d39386f45f17968591f32f3e0d638955b7e 100644 (file)
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*                         yyyymmddN */
-#define CATALOG_VERSION_NO 202203221
+#define CATALOG_VERSION_NO 202203241
 
 #endif

diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 8a5b20e62cb423fd34c310af0f00da42a13a50bb..27d19b4bf1d59c3b0f457201893b452f89f96176 100644 (file)
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -2269,19 +2269,24 @@ pg_statio_all_tables| SELECT c.oid AS relid,
     c.relname,
     (pg_stat_get_blocks_fetched(c.oid) - pg_stat_get_blocks_hit(c.oid)) AS heap_blks_read,
     pg_stat_get_blocks_hit(c.oid) AS heap_blks_hit,
-    (sum((pg_stat_get_blocks_fetched(i.indexrelid) - pg_stat_get_blocks_hit(i.indexrelid))))::bigint AS idx_blks_read,
-    (sum(pg_stat_get_blocks_hit(i.indexrelid)))::bigint AS idx_blks_hit,
+    i.idx_blks_read,
+    i.idx_blks_hit,
     (pg_stat_get_blocks_fetched(t.oid) - pg_stat_get_blocks_hit(t.oid)) AS toast_blks_read,
     pg_stat_get_blocks_hit(t.oid) AS toast_blks_hit,
-    (pg_stat_get_blocks_fetched(x.indexrelid) - pg_stat_get_blocks_hit(x.indexrelid)) AS tidx_blks_read,
-    pg_stat_get_blocks_hit(x.indexrelid) AS tidx_blks_hit
+    x.idx_blks_read AS tidx_blks_read,
+    x.idx_blks_hit AS tidx_blks_hit
    FROM ((((pg_class c
-     LEFT JOIN pg_index i ON ((c.oid = i.indrelid)))
      LEFT JOIN pg_class t ON ((c.reltoastrelid = t.oid)))
-     LEFT JOIN pg_index x ON ((t.oid = x.indrelid)))
      LEFT JOIN pg_namespace n ON ((n.oid = c.relnamespace)))
-  WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char", 'm'::"char"]))
-  GROUP BY c.oid, n.nspname, c.relname, t.oid, x.indexrelid;
+     LEFT JOIN LATERAL ( SELECT (sum((pg_stat_get_blocks_fetched(pg_index.indexrelid) - pg_stat_get_blocks_hit(pg_index.indexrelid))))::bigint AS idx_blks_read,
+            (sum(pg_stat_get_blocks_hit(pg_index.indexrelid)))::bigint AS idx_blks_hit
+           FROM pg_index
+          WHERE (pg_index.indrelid = c.oid)) i ON (true))
+     LEFT JOIN LATERAL ( SELECT (sum((pg_stat_get_blocks_fetched(pg_index.indexrelid) - pg_stat_get_blocks_hit(pg_index.indexrelid))))::bigint AS idx_blks_read,
+            (sum(pg_stat_get_blocks_hit(pg_index.indexrelid)))::bigint AS idx_blks_hit
+           FROM pg_index
+          WHERE (pg_index.indrelid = t.oid)) x ON (true))
+  WHERE (c.relkind = ANY (ARRAY['r'::"char", 't'::"char", 'm'::"char"]));
 pg_statio_sys_indexes| SELECT pg_statio_all_indexes.relid,
     pg_statio_all_indexes.indexrelid,
     pg_statio_all_indexes.schemaname,