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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