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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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29
src/backend/parser/gram.y
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@ -11,7 +11,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.693 2009/11/16 21:32:06 tgl Exp $
* $PostgreSQL: pgsql/src/backend/parser/gram.y,v 2.694 2009/11/20 20:38:10 tgl Exp $
*
* HISTORY
* AUTHOR DATE MAJOR EVENT
@ -249,6 +249,7 @@ static TypeName *TableFuncTypeName(List *columns);
%type <list> TriggerEvents TriggerOneEvent
%type <value> TriggerFuncArg
%type <node> TriggerWhen
%type <str> copy_file_name
database_name access_method_clause access_method attr_name
@ -3227,18 +3228,19 @@ AlterUserMappingStmt: ALTER USER MAPPING FOR auth_ident SERVER name alter_generi
CreateTrigStmt:
CREATE TRIGGER name TriggerActionTime TriggerEvents ON
qualified_name TriggerForSpec EXECUTE PROCEDURE
func_name '(' TriggerFuncArgs ')'
qualified_name TriggerForSpec TriggerWhen
EXECUTE PROCEDURE func_name '(' TriggerFuncArgs ')'
{
CreateTrigStmt *n = makeNode(CreateTrigStmt);
n->trigname = $3;
n->relation = $7;
n->funcname = $11;
n->args = $13;
n->funcname = $12;
n->args = $14;
n->before = $4;
n->row = $8;
n->events = intVal(linitial($5));
n->columns = (List *) lsecond($5);
n->whenClause = $9;
n->isconstraint = FALSE;
n->deferrable = FALSE;
n->initdeferred = FALSE;
@ -3246,20 +3248,20 @@ CreateTrigStmt:
$$ = (Node *)n;
}
| CREATE CONSTRAINT TRIGGER name AFTER TriggerEvents ON
qualified_name OptConstrFromTable
ConstraintAttributeSpec
FOR EACH ROW EXECUTE PROCEDURE
func_name '(' TriggerFuncArgs ')'
qualified_name OptConstrFromTable ConstraintAttributeSpec
FOR EACH ROW TriggerWhen
EXECUTE PROCEDURE func_name '(' TriggerFuncArgs ')'
{
CreateTrigStmt *n = makeNode(CreateTrigStmt);
n->trigname = $4;
n->relation = $8;
n->funcname = $16;
n->args = $18;
n->funcname = $17;
n->args = $19;
n->before = FALSE;
n->row = TRUE;
n->events = intVal(linitial($6));
n->columns = (List *) lsecond($6);
n->whenClause = $14;
n->isconstraint = TRUE;
n->deferrable = ($10 & 1) != 0;
n->initdeferred = ($10 & 2) != 0;
@ -3335,6 +3337,11 @@ TriggerForType:
| STATEMENT { $$ = FALSE; }
;
TriggerWhen:
WHEN '(' a_expr ')' { $$ = $3; }
| /*EMPTY*/ { $$ = NULL; }
;
TriggerFuncArgs:
TriggerFuncArg { $$ = list_make1($1); }
| TriggerFuncArgs ',' TriggerFuncArg { $$ = lappend($1, $3); }