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Prevent pgstats from getting confused when relkind of a relation changes

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When the relkind of a relache entry changes, because a table is converted into
a view, pgstats can get confused in 15+, leading to crashes or assertion
failures.

For HEAD, Tom fixed this in b23cd185fd5, by removing support for converting a
table to a view, removing the source of the inconsistency. This commit just
adds an assertion that a relcache entry's relkind does not change, just in
case we end up with another case of that in the future. As there's no cases of
changing relkind anymore, we can't add a test that that's handled correctly.

For 15, fix the problem by not maintaining the association with the old pgstat
entry when the relkind changes during a relcache invalidation processing. In
that case the pgstat entry needs to be unlinked first, to avoid
PgStat_TableStatus->relation getting out of sync. Also add a test reproducing
the issues.

No known problem exists in 11-14, so just add the test there.

Reported-by: vignesh C <vignesh21@gmail.com>
Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CALDaNm2yXz+zOtv7y5zBd5WKT8O0Ld3YxikuU3dcyCvxF7gypA@mail.gmail.com
Discussion: https://postgr.es/m/CALDaNm3oZA-8Wbps2Jd1g5_Gjrr-x3YWrJPek-mF5Asrrvz2Dg@mail.gmail.com
Backpatch: 15-
This commit is contained in:
Andres Freund 2022-12-02 17:50:26 -08:00
parent 01e248f796
commit af3517c15c
2 changed files with 47 additions and 1 deletions
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25
src/test/regress/expected/create_view.out
View File

@ -1776,9 +1776,32 @@ select pg_get_ruledef(oid, true) from pg_rewrite
43 AS col_b;
(1 row)
-- Test that changing the relkind of a relcache entry doesn't cause
-- trouble. Prior instances of where it did:
-- CALDaNm2yXz+zOtv7y5zBd5WKT8O0Ld3YxikuU3dcyCvxF7gypA@mail.gmail.com
-- CALDaNm3oZA-8Wbps2Jd1g5_Gjrr-x3YWrJPek-mF5Asrrvz2Dg@mail.gmail.com
CREATE TABLE tt26(c int);
BEGIN;
CREATE TABLE tt27(c int);
SAVEPOINT q;
CREATE RULE "_RETURN" AS ON SELECT TO tt27 DO INSTEAD SELECT * FROM tt26;
SELECT * FROM tt27;
c
---
(0 rows)
ROLLBACK TO q;
CREATE RULE "_RETURN" AS ON SELECT TO tt27 DO INSTEAD SELECT * FROM tt26;
ROLLBACK;
BEGIN;
CREATE TABLE tt28(c int);
CREATE RULE "_RETURN" AS ON SELECT TO tt28 DO INSTEAD SELECT * FROM tt26;
CREATE RULE "_RETURN" AS ON SELECT TO tt28 DO INSTEAD SELECT * FROM tt26;
ERROR: "tt28" is already a view
ROLLBACK;
-- clean up all the random objects we made above
\set VERBOSITY terse \\ -- suppress cascade details
DROP SCHEMA temp_view_test CASCADE;
NOTICE: drop cascades to 27 other objects
DROP SCHEMA testviewschm2 CASCADE;
NOTICE: drop cascades to 64 other objects
NOTICE: drop cascades to 65 other objects

23
src/test/regress/sql/create_view.sql
View File

@ -608,6 +608,29 @@ select pg_get_viewdef('tt23v', true);
select pg_get_ruledef(oid, true) from pg_rewrite
where ev_class = 'tt23v'::regclass and ev_type = '1';
-- Test that changing the relkind of a relcache entry doesn't cause
-- trouble. Prior instances of where it did:
-- CALDaNm2yXz+zOtv7y5zBd5WKT8O0Ld3YxikuU3dcyCvxF7gypA@mail.gmail.com
-- CALDaNm3oZA-8Wbps2Jd1g5_Gjrr-x3YWrJPek-mF5Asrrvz2Dg@mail.gmail.com
CREATE TABLE tt26(c int);
BEGIN;
CREATE TABLE tt27(c int);
SAVEPOINT q;
CREATE RULE "_RETURN" AS ON SELECT TO tt27 DO INSTEAD SELECT * FROM tt26;
SELECT * FROM tt27;
ROLLBACK TO q;
CREATE RULE "_RETURN" AS ON SELECT TO tt27 DO INSTEAD SELECT * FROM tt26;
ROLLBACK;
BEGIN;
CREATE TABLE tt28(c int);
CREATE RULE "_RETURN" AS ON SELECT TO tt28 DO INSTEAD SELECT * FROM tt26;
CREATE RULE "_RETURN" AS ON SELECT TO tt28 DO INSTEAD SELECT * FROM tt26;
ROLLBACK;
-- clean up all the random objects we made above
\set VERBOSITY terse \\ -- suppress cascade details
DROP SCHEMA temp_view_test CASCADE;