"Kevin Grittner" <[email protected]> wrote:
> Attached is a patch based on these thoughts.
OK, really attached this time.
-Kevin
*** a/src/backend/executor/execMain.c
--- b/src/backend/executor/execMain.c
***************
*** 1921,1928 **** EvalPlanQualFetch(EState *estate, Relation relation, int
lockmode,
switch (test)
{
case HeapTupleSelfUpdated:
- /* treat it as deleted; do not process
*/
ReleaseBuffer(buffer);
return NULL;
case HeapTupleMayBeUpdated:
--- 1921,1936 ----
switch (test)
{
case HeapTupleSelfUpdated:
ReleaseBuffer(buffer);
+ if (!ItemPointerEquals(&update_ctid,
&tuple.t_self))
+ {
+ /* it was updated, so look at
the updated version */
+ tuple.t_self = update_ctid;
+ /* updated row should have xmin
matching this xmax */
+ priorXmax = update_xmax;
+ continue;
+ }
+ /* treat it as deleted; do not process
*/
return NULL;
case HeapTupleMayBeUpdated:
*** a/src/backend/executor/nodeModifyTable.c
--- b/src/backend/executor/nodeModifyTable.c
***************
*** 354,359 **** ldelete:;
--- 354,398 ----
switch (result)
{
case HeapTupleSelfUpdated:
+ /*
+ * There is no sensible action to take if the
BEFORE DELETE
+ * trigger for a row issues an UPDATE for the
same row, either
+ * directly or by performing DML which fires
other triggers
+ * which do the update. We don't want to
discard the original
+ * DELETE while keeping the triggered actions
based on its
+ * deletion; and it would be no better to allow
the original
+ * DELETE while discarding some of its
triggered actions.
+ * Updating the row which is being deleted
risks losing some
+ * information which might be important
according to business
+ * rules; so throwing an error is the only safe
course.
+ *
+ * We want to be careful not to trigger this
for join/updates
+ * which join to the same row more than once,
so we check
+ * whether the tuple was expired by a command
other than the
+ * one which initially fired the trigger. If
it is, the
+ * current command ID must have changed, so do
that check
+ * first, because it is fast. If it has
changed, chase down
+ * to the last version of the row to see if it
was changed by
+ * a subsequent command.
+ */
+ if (GetCurrentCommandId(false) !=
estate->es_output_cid)
+ {
+ HeapTuple copyTuple;
+
+ copyTuple = EvalPlanQualFetch(estate,
+
resultRelationDesc,
+
LockTupleExclusive,
+
&update_ctid,
+
update_xmax);
+ if (copyTuple == NULL
+ ||
HeapTupleHeaderGetCmax(copyTuple->t_data) != estate->es_output_cid)
+ {
+ ereport(ERROR,
+
(errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
+ errmsg("cannot
update or delete a row from its BEFORE DELETE trigger"),
+
errhint("Consider moving code to an AFTER DELETE trigger.")));
+ }
+ }
/* already deleted by self; nothing to do */
return NULL;
***************
*** 570,575 **** lreplace:;
--- 609,651 ----
switch (result)
{
case HeapTupleSelfUpdated:
+ /*
+ * There is no sensible action to take if the
BEFORE UPDATE
+ * trigger for a row issues another UPDATE for
the same row,
+ * either directly or by performing DML which
fires other
+ * triggers which do the update. We don't want
to discard the
+ * original UPDATE while keeping the triggered
actions based
+ * on its update; and it would be no better to
allow the
+ * original UPDATE while discarding some of its
triggered
+ * actions.
+ *
+ * We want to be careful not to trigger this
for join/updates
+ * which join to the same row more than once,
so we check
+ * whether the tuple was expired by a command
other than the
+ * one which initially fired the trigger. If
it is, the
+ * current command ID must have changed, so do
that check
+ * first, because it is fast. If it has
changed, chase down
+ * to the last version of the row to see if it
was changed by
+ * a subsequent command.
+ */
+ if (GetCurrentCommandId(false) !=
estate->es_output_cid)
+ {
+ HeapTuple copyTuple;
+
+ copyTuple = EvalPlanQualFetch(estate,
+
resultRelationDesc,
+
LockTupleExclusive,
+
&update_ctid,
+
update_xmax);
+ if (copyTuple == NULL
+ ||
HeapTupleHeaderGetCmax(copyTuple->t_data) != estate->es_output_cid)
+ {
+ ereport(ERROR,
+
(errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
+ errmsg("cannot
update or delete a row from its BEFORE UPDATE trigger"),
+
errhint("Consider moving code to an AFTER UPDATE trigger.")));
+ }
+ }
/* already deleted by self; nothing to do */
return NULL;
*** a/src/test/regress/expected/triggers.out
--- b/src/test/regress/expected/triggers.out
***************
*** 1443,1445 **** NOTICE: drop cascades to 2 other objects
--- 1443,1566 ----
DETAIL: drop cascades to view city_view
drop cascades to view european_city_view
DROP TABLE country_table;
+ --
+ -- Test updates to rows during firing of BEFORE ROW triggers.
+ --
+ create table parent (aid int not null primary key,
+ val1 text,
+ val2 text,
+ val3 text,
+ val4 text,
+ bcnt int not null default 0);
+ NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "parent_pkey"
for table "parent"
+ create table child (bid int not null primary key,
+ aid int not null,
+ val1 text);
+ NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "child_pkey"
for table "child"
+ create function parent_upd_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ if old.val1 <> new.val1 then
+ new.val2 = new.val1;
+ delete from child where child.aid = new.aid and child.val1 = new.val1;
+ end if;
+ return new;
+ end;
+ $$;
+ create trigger parent_upd_trig before update On parent
+ for each row execute procedure parent_upd_func();
+ create function parent_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ delete from child where aid = old.aid;
+ return old;
+ end;
+ $$;
+ create trigger parent_del_trig before delete On parent
+ for each row execute procedure parent_del_func();
+ create function child_ins_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ update parent set bcnt = bcnt + 1 where aid = new.aid;
+ return new;
+ end;
+ $$;
+ create trigger child_ins_trig after insert on child
+ for each row execute procedure child_ins_func();
+ create function child_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ update parent set bcnt = bcnt - 1 where aid = old.aid;
+ return old;
+ end;
+ $$;
+ create trigger child_del_trig after delete on child
+ for each row execute procedure child_del_func();
+ insert into parent values (1, 'a', 'a', 'a', 'a', 0);
+ insert into child values (10, 1, 'b');
+ select * from parent; select * from child;
+ aid | val1 | val2 | val3 | val4 | bcnt
+ -----+------+------+------+------+------
+ 1 | a | a | a | a | 1
+ (1 row)
+
+ bid | aid | val1
+ -----+-----+------
+ 10 | 1 | b
+ (1 row)
+
+ update parent set val1 = 'b' where aid = 1;
+ ERROR: cannot update or delete a row from its BEFORE UPDATE trigger
+ HINT: Consider moving code to an AFTER UPDATE trigger.
+ select * from parent; select * from child;
+ aid | val1 | val2 | val3 | val4 | bcnt
+ -----+------+------+------+------+------
+ 1 | a | a | a | a | 1
+ (1 row)
+
+ bid | aid | val1
+ -----+-----+------
+ 10 | 1 | b
+ (1 row)
+
+ delete from parent where aid = 1;
+ ERROR: cannot update or delete a row from its BEFORE DELETE trigger
+ HINT: Consider moving code to an AFTER DELETE trigger.
+ select * from parent; select * from child;
+ aid | val1 | val2 | val3 | val4 | bcnt
+ -----+------+------+------+------+------
+ 1 | a | a | a | a | 1
+ (1 row)
+
+ bid | aid | val1
+ -----+-----+------
+ 10 | 1 | b
+ (1 row)
+
+ create or replace function parent_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ delete from child where aid = old.aid;
+ if found then
+ delete from parent where aid = old.aid;
+ return null;
+ end if;
+ return old;
+ end;
+ $$;
+ delete from parent where aid = 1;
+ select * from parent; select * from child;
+ aid | val1 | val2 | val3 | val4 | bcnt
+ -----+------+------+------+------+------
+ (0 rows)
+
+ bid | aid | val1
+ -----+-----+------
+ (0 rows)
+
+ drop table parent, child;
*** a/src/test/regress/sql/triggers.sql
--- b/src/test/regress/sql/triggers.sql
***************
*** 961,963 **** SELECT * FROM city_view;
--- 961,1050 ----
DROP TABLE city_table CASCADE;
DROP TABLE country_table;
+
+ --
+ -- Test updates to rows during firing of BEFORE ROW triggers.
+ --
+
+ create table parent (aid int not null primary key,
+ val1 text,
+ val2 text,
+ val3 text,
+ val4 text,
+ bcnt int not null default 0);
+ create table child (bid int not null primary key,
+ aid int not null,
+ val1 text);
+
+ create function parent_upd_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ if old.val1 <> new.val1 then
+ new.val2 = new.val1;
+ delete from child where child.aid = new.aid and child.val1 = new.val1;
+ end if;
+ return new;
+ end;
+ $$;
+ create trigger parent_upd_trig before update On parent
+ for each row execute procedure parent_upd_func();
+
+ create function parent_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ delete from child where aid = old.aid;
+ return old;
+ end;
+ $$;
+ create trigger parent_del_trig before delete On parent
+ for each row execute procedure parent_del_func();
+
+ create function child_ins_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ update parent set bcnt = bcnt + 1 where aid = new.aid;
+ return new;
+ end;
+ $$;
+ create trigger child_ins_trig after insert on child
+ for each row execute procedure child_ins_func();
+
+ create function child_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ update parent set bcnt = bcnt - 1 where aid = old.aid;
+ return old;
+ end;
+ $$;
+ create trigger child_del_trig after delete on child
+ for each row execute procedure child_del_func();
+
+ insert into parent values (1, 'a', 'a', 'a', 'a', 0);
+ insert into child values (10, 1, 'b');
+ select * from parent; select * from child;
+ update parent set val1 = 'b' where aid = 1;
+ select * from parent; select * from child;
+ delete from parent where aid = 1;
+ select * from parent; select * from child;
+
+ create or replace function parent_del_func()
+ returns trigger language plpgsql as
+ $$
+ begin
+ delete from child where aid = old.aid;
+ if found then
+ delete from parent where aid = old.aid;
+ return null;
+ end if;
+ return old;
+ end;
+ $$;
+
+ delete from parent where aid = 1;
+ select * from parent; select * from child;
+
+ drop table parent, child;
--
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