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Add a WHEN clause to CREATE TRIGGER, allowing a boolean expression to be

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checked to determine whether the trigger should be fired.

For BEFORE triggers this is mostly a matter of spec compliance; but for AFTER
triggers it can provide a noticeable performance improvement, since queuing of
a deferred trigger event and re-fetching of the row(s) at end of statement can
be short-circuited if the trigger does not need to be fired.

Takahiro Itagaki, reviewed by KaiGai Kohei.
This commit is contained in:
Tom Lane
2009-11-20 20:38:12 +00:00
parent 201a45c4fa
commit 7fc0f06221
27 changed files with 783 additions and 100 deletions
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3
src/include/nodes/parsenodes.h
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@@ -13,7 +13,7 @@
* Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.415 2009/11/16 21:32:07 tgl Exp $
* $PostgreSQL: pgsql/src/include/nodes/parsenodes.h,v 1.416 2009/11/20 20:38:11 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1571,6 +1571,7 @@ typedef struct CreateTrigStmt
/* events uses the TRIGGER_TYPE bits defined in catalog/pg_trigger.h */
int16 events; /* INSERT/UPDATE/DELETE/TRUNCATE */
List *columns; /* column names, or NIL for all columns */
Node *whenClause; /* qual expression, or NULL if none */
/* The following are used for constraint triggers (RI and unique checks) */
bool isconstraint; /* This is a constraint trigger */