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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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2
src/test/regress/expected/foreign_key.out
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@@ -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;