Don't use_physical_tlist for an IOS with non-returnable columns.

createplan.c tries to save a runtime projection step by specifying
a scan plan node's output as being exactly the table's columns, or
index's columns in the case of an index-only scan, if there is not a
reason to do otherwise.  This logic did not previously pay attention
to whether an index's columns are returnable.  That worked, sort of
accidentally, until commit 9a3ddeb51 taught setrefs.c to reject plans
that try to read a non-returnable column.  I have no desire to loosen
setrefs.c's new check, so instead adjust use_physical_tlist() to not
try to optimize this way when there are non-returnable column(s).

Per report from Ryan Kelly.  Like the previous patch, back-patch
to all supported branches.

Discussion: https://postgr.es/m/CAHUie24ddN+pDNw7fkhNrjrwAX=fXXfGZZEHhRuofV_N_ftaSg@mail.gmail.com

diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index cd6d72c7633447ad441535fb5de53c745918be37..fa069a217c842f6a09971d4f0ac2dc0f17140720 100644 (file)
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -914,6 +914,22 @@ use_physical_tlist(PlannerInfo *root, Path *path, int flags)
                        return false;
        }
 
+       /*
+        * For an index-only scan, the "physical tlist" is the index's indextlist.
+        * We can only return that without a projection if all the index's columns
+        * are returnable.
+        */
+       if (path->pathtype == T_IndexOnlyScan)
+       {
+               IndexOptInfo *indexinfo = ((IndexPath *) path)->indexinfo;
+
+               for (i = 0; i < indexinfo->ncolumns; i++)
+               {
+                       if (!indexinfo->canreturn[i])
+                               return false;
+               }
+       }
+
        /*
         * Also, can't do it if CP_LABEL_TLIST is specified and path is requested
         * to emit any sort/group columns that are not simple Vars.  (If they are

diff --git a/src/test/regress/expected/gist.out b/src/test/regress/expected/gist.out
index 4ba2e7f29e0a8a91f93502b9a67cd6dbbbe2fbcf..2393132ed67bf2e2feb7f28180e5cb2ab4dd94de 100644 (file)
--- a/src/test/regress/expected/gist.out
+++ b/src/test/regress/expected/gist.out
@@ -357,6 +357,22 @@ select p from gist_tbl where circle(p,1) @> circle(point(0,0),0.95);
  (0,0)
 (1 row)
 
+-- Also check that use_physical_tlist doesn't trigger in such cases.
+explain (verbose, costs off)
+select count(*) from gist_tbl;
+                             QUERY PLAN                              
+---------------------------------------------------------------------
+ Aggregate
+   Output: count(*)
+   ->  Index Only Scan using gist_tbl_multi_index on public.gist_tbl
+(3 rows)
+
+select count(*) from gist_tbl;
+ count 
+-------
+ 10001
+(1 row)
+
 -- This case isn't supported, but it should at least EXPLAIN correctly.
 explain (verbose, costs off)
 select p from gist_tbl order by circle(p,1) <-> point(0,0) limit 1;

diff --git a/src/test/regress/sql/gist.sql b/src/test/regress/sql/gist.sql
index cf1069c20727a5fdc7b1c47b8caccbbdcd6b3e0d..d94a0bb2f7552c242191f5e850efd4bc6860e668 100644 (file)
--- a/src/test/regress/sql/gist.sql
+++ b/src/test/regress/sql/gist.sql
@@ -159,6 +159,11 @@ explain (verbose, costs off)
 select p from gist_tbl where circle(p,1) @> circle(point(0,0),0.95);
 select p from gist_tbl where circle(p,1) @> circle(point(0,0),0.95);
 
+-- Also check that use_physical_tlist doesn't trigger in such cases.
+explain (verbose, costs off)
+select count(*) from gist_tbl;
+select count(*) from gist_tbl;
+
 -- This case isn't supported, but it should at least EXPLAIN correctly.
 explain (verbose, costs off)
 select p from gist_tbl order by circle(p,1) <-> point(0,0) limit 1;