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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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55
src/backend/executor/execQual.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.254 2009/11/04 22:26:05 tgl Exp $
* $PostgreSQL: pgsql/src/backend/executor/execQual.c,v 1.255 2009/11/20 20:38:10 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -491,26 +491,15 @@ ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
if (isDone)
*isDone = ExprSingleResult;
/*
* Get the input slot and attribute number we want
*
* The asserts check that references to system attributes only appear at
* the level of a relation scan; at higher levels, system attributes must
* be treated as ordinary variables (since we no longer have access to the
* original tuple).
*/
attnum = variable->varattno;
/* Get the input slot and attribute number we want */
switch (variable->varno)
{
case INNER: /* get the tuple from the inner node */
slot = econtext->ecxt_innertuple;
Assert(attnum > 0);
break;
case OUTER: /* get the tuple from the outer node */
slot = econtext->ecxt_outertuple;
Assert(attnum > 0);
break;
default: /* get the tuple from the relation being
@ -519,6 +508,8 @@ ExecEvalVar(ExprState *exprstate, ExprContext *econtext,
break;
}
attnum = variable->varattno;
if (attnum != InvalidAttrNumber)
{
/*
@ -715,7 +706,7 @@ ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone)
{
Var *variable = (Var *) exprstate->expr;
TupleTableSlot *slot = econtext->ecxt_scantuple;
TupleTableSlot *slot;
HeapTuple tuple;
TupleDesc tupleDesc;
HeapTupleHeader dtuple;
@ -724,6 +715,23 @@ ExecEvalWholeRowVar(ExprState *exprstate, ExprContext *econtext,
*isDone = ExprSingleResult;
*isNull = false;
/* Get the input slot we want */
switch (variable->varno)
{
case INNER: /* get the tuple from the inner node */
slot = econtext->ecxt_innertuple;
break;
case OUTER: /* get the tuple from the outer node */
slot = econtext->ecxt_outertuple;
break;
default: /* get the tuple from the relation being
* scanned */
slot = econtext->ecxt_scantuple;
break;
}
tuple = ExecFetchSlotTuple(slot);
tupleDesc = slot->tts_tupleDescriptor;
@ -766,7 +774,7 @@ ExecEvalWholeRowSlow(ExprState *exprstate, ExprContext *econtext,
bool *isNull, ExprDoneCond *isDone)
{
Var *variable = (Var *) exprstate->expr;
TupleTableSlot *slot = econtext->ecxt_scantuple;
TupleTableSlot *slot;
HeapTuple tuple;
TupleDesc var_tupdesc;
HeapTupleHeader dtuple;
@ -775,6 +783,23 @@ ExecEvalWholeRowSlow(ExprState *exprstate, ExprContext *econtext,
*isDone = ExprSingleResult;
*isNull = false;
/* Get the input slot we want */
switch (variable->varno)
{
case INNER: /* get the tuple from the inner node */
slot = econtext->ecxt_innertuple;
break;
case OUTER: /* get the tuple from the outer node */
slot = econtext->ecxt_outertuple;
break;
default: /* get the tuple from the relation being
* scanned */
slot = econtext->ecxt_scantuple;
break;
}
/*
* Currently, the only case handled here is stripping of trailing resjunk
* fields, which we do in a slightly chintzy way by just adjusting the