database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-07-02 09:02:37 +03:00
Code Activity

Don't add a redundant constraint when detaching a partition

Browse Source 
On ALTER TABLE .. DETACH CONCURRENTLY, we add a new table constraint
that duplicates the partition constraint.  But if the partition already
has another constraint that implies that one, then that's unnecessary.
We were already avoiding the addition of a duplicate constraint if there
was an exact 'equal' match -- this just improves the quality of the check.

Author: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/20210410184226.GY6592@telsasoft.com
This commit is contained in:
Alvaro Herrera
2021-04-21 18:12:05 -04:00
parent e014d25dea
commit 7b357cc6ae
3 changed files with 52 additions and 31 deletions
Download Patch File Download Diff File Expand all files Collapse all files

57
src/backend/commands/tablecmds.c
View File

@ -17915,47 +17915,42 @@ ATExecDetachPartitionFinalize(Relation rel, RangeVar *name)
* DetachAddConstraintIfNeeded
* Subroutine for ATExecDetachPartition. Create a constraint that
* takes the place of the partition constraint, but avoid creating
* a dupe if an equivalent constraint already exists.
* a dupe if an constraint already exists which implies the needed
* constraint.
*/
static void
DetachAddConstraintIfNeeded(List **wqueue, Relation partRel)
{
AlteredTableInfo *tab;
Expr *constraintExpr;
TupleDesc td = RelationGetDescr(partRel);
Constraint *n;
List *constraintExpr;
constraintExpr = make_ands_explicit(RelationGetPartitionQual(partRel));
constraintExpr = RelationGetPartitionQual(partRel);
constraintExpr = (List *) eval_const_expressions(NULL, (Node *) constraintExpr);
/* If an identical constraint exists, we don't need to create one */
if (td->constr && td->constr->num_check > 0)
/*
* Avoid adding a new constraint if the needed constraint is implied by an
* existing constraint
*/
if (!PartConstraintImpliedByRelConstraint(partRel, constraintExpr))
{
for (int i = 0; i < td->constr->num_check; i++)
{
Node *thisconstr;
AlteredTableInfo *tab;
Constraint *n;
thisconstr = stringToNode(td->constr->check[i].ccbin);
tab = ATGetQueueEntry(wqueue, partRel);
if (equal(constraintExpr, thisconstr))
return;
}
/* Add constraint on partition, equivalent to the partition constraint */
n = makeNode(Constraint);
n->contype = CONSTR_CHECK;
n->conname = NULL;
n->location = -1;
n->is_no_inherit = false;
n->raw_expr = NULL;
n->cooked_expr = nodeToString(make_ands_explicit(constraintExpr));
n->initially_valid = true;
n->skip_validation = true;
/* It's a re-add, since it nominally already exists */
ATAddCheckConstraint(wqueue, tab, partRel, n,
true, false, true, ShareUpdateExclusiveLock);
}
tab = ATGetQueueEntry(wqueue, partRel);
/* Add constraint on partition, equivalent to the partition constraint */
n = makeNode(Constraint);
n->contype = CONSTR_CHECK;
n->conname = NULL;
n->location = -1;
n->is_no_inherit = false;
n->raw_expr = NULL;
n->cooked_expr = nodeToString(constraintExpr);
n->initially_valid = true;
n->skip_validation = true;
/* It's a re-add, since it nominally already exists */
ATAddCheckConstraint(wqueue, tab, partRel, n,
true, false, true, ShareUpdateExclusiveLock);
}
/*