From 7b357cc6ae553c0ecacdc11b2e5278b7bf477dba Mon Sep 17 00:00:00 2001 From: Alvaro Herrera Date: Wed, 21 Apr 2021 18:12:05 -0400 Subject: Don't add a redundant constraint when detaching a partition MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reviewed-by: Álvaro Herrera Discussion: https://postgr.es/m/20210410184226.GY6592@telsasoft.com --- src/backend/commands/tablecmds.c | 61 ++++++++++++++++++---------------------- 1 file changed, 28 insertions(+), 33 deletions(-) (limited to 'src/backend/commands/tablecmds.c') diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c index 096a6f28915..97cc9fd6eca 100644 --- a/src/backend/commands/tablecmds.c +++ b/src/backend/commands/tablecmds.c @@ -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; - - thisconstr = stringToNode(td->constr->check[i].ccbin); - - if (equal(constraintExpr, thisconstr)) - return; - } + AlteredTableInfo *tab; + Constraint *n; + + 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(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); } /* -- cgit v1.2.3