From 13f1e9f26a112623c07f55b88b87530649d7155d Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 29 Jun 2025 13:56:03 -0400 Subject: [PATCH] Obtain required table lock during cross-table constraint updates. Sometimes a table's constraint may depend on a column of another table, so that we have to update the constraint when changing the referenced column's type. We need to have lock on the constraint's table to do that. ATPostAlterTypeCleanup believed that this case was only possible for FOREIGN KEY constraints, but it's wrong at least for CHECK and EXCLUDE constraints; and in general, we'd probably need exclusive lock to alter any sort of constraint. So just remove the contype check and acquire lock for any other table. This prevents a "you don't have lock" assertion failure, though no ill effect is observed in production builds. We'll error out later anyway because we don't presently support physically altering column types within stored composite columns. But the catalog-munging is basically all there, so we may as well make that part work. Bug: #18970 Reported-by: Alexander Lakhin Diagnosed-by: jian he Author: Tom Lane Discussion: https://postgr.es/m/18970-a7d1cfe1f8d5d8d9@postgresql.org Backpatch-through: 13 --- src/backend/commands/tablecmds.c | 21 +++++++++++---------- src/test/regress/expected/alter_table.out | 7 +++++++ src/test/regress/sql/alter_table.sql | 9 +++++++++ 3 files changed, 27 insertions(+), 10 deletions(-) diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 53dc3296c81..3c680fade2b 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -12560,9 +12560,12 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) /* * Re-parse the index and constraint definitions, and attach them to the * appropriate work queue entries. We do this before dropping because in - * the case of a FOREIGN KEY constraint, we might not yet have exclusive - * lock on the table the constraint is attached to, and we need to get - * that before reparsing/dropping. + * the case of a constraint on another table, we might not yet have + * exclusive lock on the table the constraint is attached to, and we need + * to get that before reparsing/dropping. (That's possible at least for + * FOREIGN KEY, CHECK, and EXCLUSION constraints; in non-FK cases it + * requires a dependency on the target table's composite type in the other + * table's constraint expressions.) * * We can't rely on the output of deparsing to tell us which relation to * operate on, because concurrent activity might have made the name @@ -12578,7 +12581,6 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) Form_pg_constraint con; Oid relid; Oid confrelid; - char contype; bool conislocal; tup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(oldId)); @@ -12595,7 +12597,6 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) elog(ERROR, "could not identify relation associated with constraint %u", oldId); } confrelid = con->confrelid; - contype = con->contype; conislocal = con->conislocal; ReleaseSysCache(tup); @@ -12612,12 +12613,12 @@ ATPostAlterTypeCleanup(List **wqueue, AlteredTableInfo *tab, LOCKMODE lockmode) continue; /* - * When rebuilding an FK constraint that references the table we're - * modifying, we might not yet have any lock on the FK's table, so get - * one now. We'll need AccessExclusiveLock for the DROP CONSTRAINT - * step, so there's no value in asking for anything weaker. + * When rebuilding another table's constraint that references the + * table we're modifying, we might not yet have any lock on the other + * table, so get one now. We'll need AccessExclusiveLock for the DROP + * CONSTRAINT step, so there's no value in asking for anything weaker. */ - if (relid != tab->relid && contype == CONSTRAINT_FOREIGN) + if (relid != tab->relid) LockRelationOid(relid, AccessExclusiveLock); ATPostAlterTypeParse(oldId, relid, confrelid, diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out index 28afffad2f0..fe3f2f009dc 100644 --- a/src/test/regress/expected/alter_table.out +++ b/src/test/regress/expected/alter_table.out @@ -4508,6 +4508,13 @@ create trigger xtrig update bar1 set a = a + 1; INFO: a=1, b=1 /* End test case for bug #16242 */ +/* Test case for bug #18970 */ +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 +drop table attbl, atref; +/* End test case for bug #18970 */ -- Test that ALTER TABLE rewrite preserves a clustered index -- for normal indexes and indexes on constraints. create table alttype_cluster (a int); diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql index d1b9f067152..06bcbb04c46 100644 --- a/src/test/regress/sql/alter_table.sql +++ b/src/test/regress/sql/alter_table.sql @@ -2978,6 +2978,15 @@ update bar1 set a = a + 1; /* End test case for bug #16242 */ +/* Test case for bug #18970 */ + +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 +drop table attbl, atref; + +/* End test case for bug #18970 */ + -- Test that ALTER TABLE rewrite preserves a clustered index -- for normal indexes and indexes on constraints. create table alttype_cluster (a int); -- 2.39.5