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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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67
src/backend/utils/adt/ruleutils.c
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@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.314 2009/11/05 23:24:25 tgl Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/ruleutils.c,v 1.315 2009/11/20 20:38:11 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -487,6 +487,8 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
SysScanDesc tgscan;
int findx = 0;
char *tgname;
Datum value;
bool isnull;
/*
* Fetch the pg_trigger tuple by the Oid of the trigger
@ -543,6 +545,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
appendStringInfo(&buf, " OR UPDATE");
else
appendStringInfo(&buf, " UPDATE");
findx++;
/* tgattr is first var-width field, so OK to access directly */
if (trigrec->tgattr.dim1 > 0)
{
@ -567,6 +570,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
appendStringInfo(&buf, " OR TRUNCATE");
else
appendStringInfo(&buf, " TRUNCATE");
findx++;
}
appendStringInfo(&buf, " ON %s",
generate_relation_name(trigrec->tgrelid, NIL));
@ -574,7 +578,7 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
if (trigrec->tgisconstraint)
{
if (trigrec->tgconstrrelid != InvalidOid)
if (OidIsValid(trigrec->tgconstrrelid))
{
appendStringInfo(&buf, "FROM %s",
generate_relation_name(trigrec->tgconstrrelid, NIL));
@ -596,23 +600,70 @@ pg_get_triggerdef_worker(Oid trigid, bool pretty)
appendStringInfo(&buf, "FOR EACH STATEMENT");
appendStringInfoString(&buf, pretty ? "\n " : " ");
/* If the trigger has a WHEN qualification, add that */
value = fastgetattr(ht_trig, Anum_pg_trigger_tgqual,
tgrel->rd_att, &isnull);
if (!isnull)
{
Node *qual;
deparse_context context;
deparse_namespace dpns;
RangeTblEntry *oldrte;
RangeTblEntry *newrte;
appendStringInfoString(&buf, "WHEN (");
qual = stringToNode(TextDatumGetCString(value));
/* Build minimal OLD and NEW RTEs for the rel */
oldrte = makeNode(RangeTblEntry);
oldrte->rtekind = RTE_RELATION;
oldrte->relid = trigrec->tgrelid;
oldrte->eref = makeAlias("old", NIL);
oldrte->inh = false;
oldrte->inFromCl = true;
newrte = makeNode(RangeTblEntry);
newrte->rtekind = RTE_RELATION;
newrte->relid = trigrec->tgrelid;
newrte->eref = makeAlias("new", NIL);
newrte->inh = false;
newrte->inFromCl = true;
/* Build two-element rtable */
dpns.rtable = list_make2(oldrte, newrte);
dpns.ctes = NIL;
dpns.subplans = NIL;
dpns.outer_plan = dpns.inner_plan = NULL;
/* Set up context with one-deep namespace stack */
context.buf = &buf;
context.namespaces = list_make1(&dpns);
context.windowClause = NIL;
context.windowTList = NIL;
context.varprefix = true;
context.prettyFlags = pretty ? PRETTYFLAG_PAREN | PRETTYFLAG_INDENT : 0;
context.indentLevel = PRETTYINDENT_STD;
get_rule_expr(qual, &context, false);
appendStringInfo(&buf, ")%s", pretty ? "\n " : " ");
}
appendStringInfo(&buf, "EXECUTE PROCEDURE %s(",
generate_function_name(trigrec->tgfoid, 0,
NIL, NULL, NULL));
if (trigrec->tgnargs > 0)
{
bytea *val;
bool isnull;
char *p;
int i;
val = DatumGetByteaP(fastgetattr(ht_trig,
Anum_pg_trigger_tgargs,
tgrel->rd_att, &isnull));
value = fastgetattr(ht_trig, Anum_pg_trigger_tgargs,
tgrel->rd_att, &isnull);
if (isnull)
elog(ERROR, "tgargs is null for trigger %u", trigid);
p = (char *) VARDATA(val);
p = (char *) VARDATA(DatumGetByteaP(value));
for (i = 0; i < trigrec->tgnargs; i++)
{
if (i > 0)