From e6dd6e6ee6e1443441088173231fe9085ce4b912 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 3 Jul 2025 13:46:07 -0400 Subject: [PATCH] Obtain required table lock during cross-table updates, redux. Commits 8319e5cb5 et al missed the fact that ATPostAlterTypeCleanup contains three calls to ATPostAlterTypeParse, and the other two also need protection against passing a relid that we don't yet have lock on. Add similar logic to those code paths, and add some test cases demonstrating the need for it. In v18 and master, the test cases demonstrate that there's a behavioral discrepancy between stored generated columns and virtual generated columns: we disallow changing the expression of a stored column if it's used in any composite-type columns, but not that of a virtual column. Since the expression isn't actually relevant to either sort of composite-type usage, this prohibition seems unnecessary; but changing it is a matter for separate discussion. For now we are just documenting the existing behavior. Reported-by: jian he Author: jian he Reviewed-by: Tom Lane Discussion: CACJufxGKJtGNRRSXfwMW9SqVOPEMdP17BJ7DsBf=tNsv9pWU9g@mail.gmail.com Backpatch-through: 13 --- src/backend/commands/tablecmds.c | 22 ++++++++++++++++++++++ src/test/regress/expected/alter_table.out | 8 ++++++++ src/test/regress/sql/alter_table.sql | 8 ++++++++ 3 files changed, 38 insertions(+) diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 2f649ba7582..9819067ad9d 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -13533,6 +13533,14 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) Oid relid; relid = IndexGetRelation(oldId, false); + + /* + * As above, make sure we have lock on the index's table if it's not + * the same table. + */ + if (relid != tab->relid) + LockRelationOid(relid, AccessExclusiveLock); + ATPostAlterTypeParse(oldId, relid, InvalidOid, (char *) lfirst(def_item), wqueue, lockmode, tab->rewrite); @@ -13549,6 +13557,20 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) Oid relid; relid = StatisticsGetRelation(oldId, false); + + /* + * As above, make sure we have lock on the statistics object's table + * if it's not the same table. However, we take + * ShareUpdateExclusiveLock here, aligning with the lock level used in + * CreateStatistics and RemoveStatisticsById. + * + * CAUTION: this should be done after all cases that grab + * AccessExclusiveLock, else we risk causing deadlock due to needing + * to promote our table lock. + */ + if (relid != tab->relid) + LockRelationOid(relid, ShareUpdateExclusiveLock); + ATPostAlterTypeParse(oldId, relid, InvalidOid, (char *) lfirst(def_item), wqueue, lockmode, tab->rewrite); diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out index e1636d3f82e..5b9c61914fd 100644 --- a/src/test/regress/expected/alter_table.out +++ b/src/test/regress/expected/alter_table.out @@ -4580,6 +4580,14 @@ create table attbl(a int); create table atref(b attbl check ((b).a is not null)); alter table attbl alter column a type numeric; -- someday this should work ERROR: cannot alter table "attbl" because column "atref.b" uses its row type +alter table atref drop constraint atref_b_check; +create statistics atref_stat on ((b).a is not null) from atref; +alter table attbl alter column a type numeric; -- someday this should work +ERROR: cannot alter table "attbl" because column "atref.b" uses its row type +drop statistics atref_stat; +create index atref_idx on atref (((b).a)); +alter table attbl alter column a type numeric; -- someday this should work +ERROR: cannot alter table "attbl" because column "atref.b" uses its row type drop table attbl, atref; /* End test case for bug #18970 */ -- Test that ALTER TABLE rewrite preserves a clustered index diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql index 43c3c728403..87d6a93b124 100644 --- a/src/test/regress/sql/alter_table.sql +++ b/src/test/regress/sql/alter_table.sql @@ -3019,6 +3019,14 @@ drop table attbl, atref; create table attbl(a int); create table atref(b attbl check ((b).a is not null)); alter table attbl alter column a type numeric; -- someday this should work +alter table atref drop constraint atref_b_check; + +create statistics atref_stat on ((b).a is not null) from atref; +alter table attbl alter column a type numeric; -- someday this should work +drop statistics atref_stat; + +create index atref_idx on atref (((b).a)); +alter table attbl alter column a type numeric; -- someday this should work drop table attbl, atref; /* End test case for bug #18970 */ -- 2.39.5