Re: Unused table of view

>>>>> "Tom" == Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

Tom> Laurent Martelli <laurent(at)aopsys(dot)com> writes:
>> The pictures table is scanned, but it's not needed.

Tom> Yes it is. For example, if pictures is empty then the view
Tom> yields zero rows. Omitting the join to pictures could give a
Tom> different result.

Since Permission is like this:

CREATE TABLE permissions (
GroupID integer NOT NULL REFERENCES groups ON DELETE cascade,
PictureID integer NOT NULL REFERENCES pictures ON DELETE cascade,
UNIQUE (GroupID, PictureID));

if the pictures table is empty, so is permissions, because
permissions.PictureID references pictures.

--
Laurent Martelli
laurent(at)aopsys(dot)com Java Aspect Components
http://www.aopsys.com/ http://jac.objectweb.org