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Fix ALTER TABLE DETACH for inconsistent indexes

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When a partitioned table has an index that doesn't support a constraint,
but a partition has an equivalent index that does, then a DETACH
operation would misbehave: a crash in assertion-enabled systems (because
we fail to find the constraint in the parent that we expect to), or a
broken coninhcount value (-1) in production systems (because we blindly
believe that we've successfully detached the parent).

While we should reject an ATTACH of a partition with such an index, we
have failed to do so in existing releases, so adding an error in stable
releases might break the (unlikely) existing applications that rely on
this behavior.  At this point I don't even want to reject them in
master, because it'd break pg_upgrade if such databases exist, and there
would be no easy way to fix existing databases without expensive index
rebuilds.

(Later on we could add ALTER TABLE ... ADD CONSTRAINT USING INDEX to
partitioned tables, which would allow the user to fix such patterns.  At
that point we could add more restrictions to prevent the problem from
its root.)

Also, add a test case that leaves one table in this condition, so that
we can verify that pg_upgrade continues to work if we later decide to
change the policy on the master branch.

Backpatch to all supported branches.

Co-authored-by: Tender Wang <tndrwang@gmail.com>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/18500-62948b6fe5522f56@postgresql.org
This commit is contained in:
Alvaro Herrera
2024-07-12 12:54:01 +02:00
parent ae4e072bad
commit 30ca4e1ab1
3 changed files with 95 additions and 4 deletions
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17
src/backend/commands/tablecmds.c
View File

@ -19299,22 +19299,31 @@ DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
foreach(cell, indexes)
{
Oid idxid = lfirst_oid(cell);
Oid parentidx;
Relation idx;
Oid constrOid;
Oid parentConstrOid;
if (!has_superclass(idxid))
continue;
Assert((IndexGetRelation(get_partition_parent(idxid, false), false) ==
RelationGetRelid(rel)));
parentidx = get_partition_parent(idxid, false);
Assert((IndexGetRelation(parentidx, false) == RelationGetRelid(rel)));
idx = index_open(idxid, AccessExclusiveLock);
IndexSetParentIndex(idx, InvalidOid);
/* If there's a constraint associated with the index, detach it too */
/*
* If there's a constraint associated with the index, detach it too.
* Careful: it is possible for a constraint index in a partition to be
* the child of a non-constraint index, so verify whether the parent
* index does actually have a constraint.
*/
constrOid = get_relation_idx_constraint_oid(RelationGetRelid(partRel),
idxid);
if (OidIsValid(constrOid))
parentConstrOid = get_relation_idx_constraint_oid(RelationGetRelid(rel),
parentidx);
if (OidIsValid(parentConstrOid) && OidIsValid(constrOid))
ConstraintSetParentConstraint(constrOid, InvalidOid, InvalidOid);
index_close(idx, NoLock);