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Change FK trigger naming convention to fix self-referential FKs.

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Use names like "RI_ConstraintTrigger_a_NNNN" for FK action triggers and
"RI_ConstraintTrigger_c_NNNN" for FK check triggers.  This ensures the
action trigger fires first in self-referential cases where the very same
row update fires both an action and a check trigger.  This change provides
a non-probabilistic solution for bug #6268, at the risk that it could break
client code that is making assumptions about the exact names assigned to
auto-generated FK triggers.  Hence, change this in HEAD only.  No need for
forced initdb since old triggers continue to work fine.
This commit is contained in:
Tom Lane 2011-10-26 13:19:42 -04:00
parent 58958726ff
commit 1e3b21dd5e
1 changed files with 12 additions and 14 deletions
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26
src/backend/commands/tablecmds.c
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@ -6467,8 +6467,17 @@ CreateFKCheckTrigger(RangeVar *myRel, Constraint *fkconstraint,
{ {
CreateTrigStmt *fk_trigger; CreateTrigStmt *fk_trigger;
/*
* Note: for a self-referential FK (referencing and referenced tables are
* the same), it is important that the ON UPDATE action fires before the
* CHECK action, since both triggers will fire on the same row during an
* UPDATE event; otherwise the CHECK trigger will be checking a non-final
* state of the row. Triggers fire in name order, so we ensure this by
* using names like "RI_ConstraintTrigger_a_NNNN" for the action triggers
* and "RI_ConstraintTrigger_c_NNNN" for the check triggers.
*/
fk_trigger = makeNode(CreateTrigStmt); fk_trigger = makeNode(CreateTrigStmt);
fk_trigger->trigname = "RI_ConstraintTrigger"; fk_trigger->trigname = "RI_ConstraintTrigger_c";
fk_trigger->relation = myRel; fk_trigger->relation = myRel;
fk_trigger->row = true; fk_trigger->row = true;
fk_trigger->timing = TRIGGER_TYPE_AFTER; fk_trigger->timing = TRIGGER_TYPE_AFTER;
@ -6524,7 +6533,7 @@ createForeignKeyTriggers(Relation rel, Constraint *fkconstraint,
* DELETE action on the referenced table. * DELETE action on the referenced table.
*/ */
fk_trigger = makeNode(CreateTrigStmt); fk_trigger = makeNode(CreateTrigStmt);
fk_trigger->trigname = "RI_ConstraintTrigger"; fk_trigger->trigname = "RI_ConstraintTrigger_a";
fk_trigger->relation = fkconstraint->pktable; fk_trigger->relation = fkconstraint->pktable;
fk_trigger->row = true; fk_trigger->row = true;
fk_trigger->timing = TRIGGER_TYPE_AFTER; fk_trigger->timing = TRIGGER_TYPE_AFTER;
@ -6577,7 +6586,7 @@ createForeignKeyTriggers(Relation rel, Constraint *fkconstraint,
* UPDATE action on the referenced table. * UPDATE action on the referenced table.
*/ */
fk_trigger = makeNode(CreateTrigStmt); fk_trigger = makeNode(CreateTrigStmt);
fk_trigger->trigname = "RI_ConstraintTrigger"; fk_trigger->trigname = "RI_ConstraintTrigger_a";
fk_trigger->relation = fkconstraint->pktable; fk_trigger->relation = fkconstraint->pktable;
fk_trigger->row = true; fk_trigger->row = true;
fk_trigger->timing = TRIGGER_TYPE_AFTER; fk_trigger->timing = TRIGGER_TYPE_AFTER;
@ -6628,17 +6637,6 @@ createForeignKeyTriggers(Relation rel, Constraint *fkconstraint,
/* /*
* Build and execute CREATE CONSTRAINT TRIGGER statements for the CHECK * Build and execute CREATE CONSTRAINT TRIGGER statements for the CHECK
* action for both INSERTs and UPDATEs on the referencing table. * action for both INSERTs and UPDATEs on the referencing table.
*
* Note: for a self-referential FK (referencing and referenced tables are
* the same), it is important that the ON UPDATE action fires before the
* CHECK action, since both triggers will fire on the same row during an
* UPDATE event; otherwise the CHECK trigger will be checking a non-final
* state of the row. Because triggers fire in name order, we are
* effectively relying on the OIDs of the triggers to sort correctly as
* text. This will work except when the OID counter wraps around or adds
* a digit, eg "99999" sorts after "100000". That is infrequent enough,
* and the use of self-referential FKs is rare enough, that we live with
* it for now. There will be a real fix in PG 9.2.
*/ */
CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, true); CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, true);
CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, false); CreateFKCheckTrigger(myRel, fkconstraint, constraintOid, indexOid, false);