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Avoid primary key lookup (and lock) if foreign key does not change

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on UPDATE.

This get's rid of the long standing annoyance that updating a row
that has foreign keys locks all the referenced rows even if the
foreign key values do not change.

The trick is to actually do a check identical to NO ACTION after an
eventually done UPDATE in the SET DEFAULT case. Since a SET DEFAULT
operation should have moved referencing rows to a new "home", a following
NO ACTION check can only fail if the column defaults of the referencing
table resulted in the key we actually deleted. Thanks to Stephan.

Jan
This commit is contained in:
Jan Wieck 2003-04-07 20:30:38 +00:00
parent afe1185cf0
commit cd203f3395
2 changed files with 34 additions and 8 deletions
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40
src/backend/utils/adt/ri_triggers.c
View File

@ -17,7 +17,7 @@
*
* Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
*
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.48 2003/03/27 19:25:40 tgl Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/adt/ri_triggers.c,v 1.49 2003/04/07 20:30:38 wieck Exp $
*
* ----------
*/
@ -395,13 +395,19 @@ RI_FKey_check(PG_FUNCTION_ARGS)
}
/*
* Note: We cannot avoid the check on UPDATE, even if old and new key
* are the same. Otherwise, someone could DELETE the PK that consists
* of the DEFAULT values, and if there are any references, a ON DELETE
* SET DEFAULT action would update the references to exactly these
* values but we wouldn't see that weird case (this is the only place
* to see it).
* No need to check anything if old and new references are the
* same on UPDATE.
*/
if (TRIGGER_FIRED_BY_UPDATE(trigdata->tg_event))
{
if (ri_KeysEqual(fk_rel, old_row, new_row, &qkey,
RI_KEYPAIR_FK_IDX))
{
heap_close(pk_rel, RowShareLock);
return PointerGetDatum(NULL);
}
}
if (SPI_connect() != SPI_OK_CONNECT)
elog(ERROR, "SPI_connect() failed in RI_FKey_check()");
@ -2397,6 +2403,16 @@ RI_FKey_setdefault_del(PG_FUNCTION_ARGS)
heap_close(fk_rel, RowExclusiveLock);
/*
* In the case we delete the row who's key is equal to the
* default values AND a referencing row in the foreign key
* table exists, we would just have updated it to the same
* values. We need to do another lookup now and in case a
* reference exists, abort the operation. That is already
* implemented in the NO ACTION trigger.
*/
RI_FKey_noaction_del(fcinfo);
return PointerGetDatum(NULL);
/*
@ -2635,6 +2651,16 @@ RI_FKey_setdefault_upd(PG_FUNCTION_ARGS)
heap_close(fk_rel, RowExclusiveLock);
/*
* In the case we updated the row who's key was equal to the
* default values AND a referencing row in the foreign key
* table exists, we would just have updated it to the same
* values. We need to do another lookup now and in case a
* reference exists, abort the operation. That is already
* implemented in the NO ACTION trigger.
*/
RI_FKey_noaction_upd(fcinfo);
return PointerGetDatum(NULL);
/*

2
src/test/regress/expected/foreign_key.out
View File

@ -882,7 +882,7 @@ delete from pktable where base1=2;
ERROR: $1 referential integrity violation - key (base1,ptest1)=(2,2) in pktable still referenced from pktable
-- fails (1,1) is being referenced (twice)
update pktable set base1=3 where base1=1;
ERROR: $1 referential integrity violation - key (base2,ptest2)=(1,1) referenced from pktable not found in pktable
ERROR: $1 referential integrity violation - key (base1,ptest1)=(1,1) in pktable still referenced from pktable
-- this sequence of two deletes will work, since after the first there will be no (2,*) references
delete from pktable where base2=2;
delete from pktable where base1=2;