referential integrity

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It seems that cascading across multiple tables does not work
correctly, when combining different action types. For example, given:

CREATE TABLE a (anum Integer PRIMARY KEY);
CREATE TABLE b (bnum Integer PRIMARY KEY,
anum Integer REFERENCES a ON DELETE CASCADE);
CREATE TABLE c (cnum Integer PRIMARY KEY,
bnum Integer REFERENCES b ON DELETE CASCADE,
anum Integer REFERENCES a ON DELETE SET NULL);

INSERT INTO a (anum) VALUES (1);
INSERT INTO b (bnum, anum) VALUES (1,1);
INSERT INTO c (cnum, bnum, anum) VALUES (1,1,1);

This passes without an error:

delete from b where bnum = 1;
delete from a where anum = 1;

but this fails:

delete from a where anum = 1;

with this error:

ERROR: <unnamed> referential integrity violation - key referenced from c
not found in b

Got any ideas? :o

Ian Turner
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