Ottó Havasvölgyi wrote:
Hi all,
Is PostgreSQL able to throw unnecessary joins?
For example I have two tables, and I join then with their primary keys,
say type of bigint . In this case if I don't reference to one of the
tables anywhere except the join condition, then the join can be eliminated.
Or if I do a "table1 left join table2 (table1.referer=table2.id)" (N :
1 relationship), and I don't reference table2 anywhere else, then it is
unnecessary.
It cannot possibly remove "unnecessary joins", simply because the join
influences whether a tuple in the referenced table gets selected and how many times.
Alex
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