Hi,
We ran into a problem on 9.0beta3 with check constraints using table
inheritance in a multi-level hierarchy with multiple inheritance.
A test script is provided below and a proposed patch is attached to this
email.
Regards,
Henk Enting, Yeb Havinga
MGRID B.V.
http://www.mgrid.net
/*
First, create a local inheritance structure:
level_0_parent
level_0_child inherits level_0_parent
This structure is the base level. The table definition and also check
constraints are defined on this level.
Add two levels that inherit this structure:
level_1_parent inherits level_0_parent
level_1_child inherits level_1_parent, level_0_child
level_2_parent inherits level_1_parent
level_2_child inherits level_2_parent, level_1_child
BTW: there is a reason that we want e.g. level_1_child to inherit from
both level_1_parent and level_0_child:
we want the data of level_1_child to be visible in both level_0_child
and level_1_parent
*/
DROP SCHEMA IF EXISTS test_inheritance CASCADE;
CREATE SCHEMA test_inheritance;
SET search_path TO test_inheritance;
CREATE TABLE level_0_parent (i int);
CREATE TABLE level_0_child (a text) INHERITS (level_0_parent);
CREATE TABLE level_1_parent() INHERITS (level_0_parent);
CREATE TABLE level_1_child() INHERITS (level_0_child, level_1_parent);
CREATE TABLE level_2_parent() INHERITS (level_1_parent);
CREATE TABLE level_2_child() INHERITS (level_1_child, level_2_parent);
-- Now add a check constraint on the top level table:
ALTER TABLE level_0_parent ADD CONSTRAINT a_check_constraint CHECK (i IN
(0,1));
/*
Check the "coninhcount" attribute of pg_constraint
Doxygen says this about the parameter:
coninhcount: Number of times inherited from direct parent relation(s)
On our machine (running 9.0beta3) the query below returns a
coninhcount of 3 for the level_2_child table.
This doesn't seem correct because the table only has two direct
parents.
*/
SELECT t.oid, t.relname, c.coninhcount
FROM pg_class t
JOIN pg_constraint c ON (c.conrelid = t.oid)
JOIN pg_namespace n ON (t.relnamespace = n.oid)
WHERE n.nspname = 'test_inheritance'
ORDER BY t.oid;
-- Next, drop the constraint on the top level table
ALTER TABLE level_0_parent DROP CONSTRAINT a_check_constraint;
/*
The constraint should now be dropped from all the tables in the
hierarchy, but the constraint hasn't been dropped on the level_2_child
table. It is still there and has a coninhcount of 1.
*/
SELECT t.oid, t.relname, c.conname, c.coninhcount
FROM pg_class t
JOIN pg_constraint c ON (c.conrelid = t.oid)
JOIN pg_namespace n ON (t.relnamespace = n.oid)
WHERE n.nspname = 'test_inheritance'
ORDER BY t.oid;
/*
Trying to drop this constraint that shouldn't be there anymore won't work.
The "drop constraint" statement below returns:
ERROR: cannot drop inherited constraint "a_check_constraint" of
relation "level_2_child"
NB after fixing this bug, the statement should return
"constraint does not exist"
*/
ALTER TABLE level_2_child DROP CONSTRAINT a_check_constraint;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 5f6fe41..d23dcdc 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -96,6 +96,17 @@ typedef struct OnCommitItem
SubTransactionId deleting_subid;
} OnCommitItem;
+/*
+ * Visit information needed to prevent redundant constraint merges. This
+ * structure is needed to prevent faulty increments of coninhcount in the case
+ * of a multiple inheritance tree that has multiple paths to a parent.
+ */
+typedef struct ParentVisit
+{
+ Oid parent;
+ Oid child;
+} ParentVisit;
+
static List *on_commits = NIL;
@@ -300,7 +311,7 @@ static void ATExecAddConstraint(List **wqueue,
static void ATAddCheckConstraint(List **wqueue,
AlteredTableInfo *tab, Relation rel,
Constraint *constr,
- bool recurse, bool recursing);
+ bool recurse, bool recursing, List
*visited);
static void ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
Constraint *fkconstraint);
static void ATExecDropConstraint(Relation rel, const char *constrName,
@@ -4584,7 +4595,7 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab,
Relation rel,
{
case CONSTR_CHECK:
ATAddCheckConstraint(wqueue, tab, rel,
- newConstraint,
recurse, false);
+ newConstraint,
recurse, false, NIL);
break;
case CONSTR_FOREIGN:
@@ -4639,7 +4650,7 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab,
Relation rel,
*/
static void
ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
- Constraint *constr, bool recurse, bool
recursing)
+ Constraint *constr, bool recurse, bool
recursing, List *visited)
{
List *newcons;
ListCell *lcon;
@@ -4711,6 +4722,30 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo
*tab, Relation rel,
Oid childrelid = lfirst_oid(child);
Relation childrel;
AlteredTableInfo *childtab;
+ ListCell *lv;
+ bool skip = false;
+ ParentVisit *visit;
+
+ /* Skip children that were visited from the same direct parent.
*/
+ foreach(lv, visited)
+ {
+ visit = lfirst(lv);
+
+ if ((visit->parent == RelationGetRelid(rel)) &&
+ (visit->child == childrelid))
+ {
+ skip = true;
+ break;
+ }
+ }
+
+ if (skip)
+ continue;
+
+ visit = (ParentVisit *) palloc(sizeof(ParentVisit));
+ visit->parent = RelationGetRelid(rel);
+ visit->child = childrelid;
+ visited = lappend(visited, visit);
/* find_inheritance_children already got lock */
childrel = heap_open(childrelid, NoLock);
@@ -4721,7 +4756,7 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo
*tab, Relation rel,
/* Recurse to child */
ATAddCheckConstraint(wqueue, childtab, childrel,
- constr, recurse, true);
+ constr, recurse, true,
visited);
heap_close(childrel, NoLock);
}
--
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