Re: foreign key is it a real key

John Fabiani <johnf(at)jfcomputer(dot)com> wrote:

> Hi,
> I have read a few articles and I'm not sure if it's me or the authors but I do
> not believe my question was answered.
>
> If I have table that has a PK and a FK - will the planner use the FK just same
> as it would use the PK? IOW's is a FK also an index used by the planner?
>
> I have a lagacy table that contains a FK constraint (vendor_id -->
> vendor_info). I believe I need an index to improve the performance of a query
> because I'm using the column as part of my join. Explain does not appear to
> use it as an index (instead of a seq scan it uses a hash join). But the table
> all ready has a FK key contraint on the column.

Yes, for large tables you have to create a own index on your fk-column.

Andreas
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