Re: Index scan troubles

Markus Wanner <markus@bluegap.ch> writes:

> Hi,
>
> I'm having a hard time using an index scan. So far, I've done quite well with
> ScanKeyInit for equality searches. But now I need to scan an index from a given
> starting point. Something like:
>
>    (x, y, z,...) > (const, const, const,...)
>
> For the equality operatior, I've used get_sort_group_operators() in combination
> with get_opcode() to pass that on as the sk_func of the scan key. I slowly
> begin to doubt if that's correct at all.

It's right for your equality case which is effectively x=const, y=const,
z=const. It's not for row comparisons case for which you need a funny "header"
ScanKey. See the comments in access/skey.h, search for "row comparisons". I'm
not sure if there's a function to create this for you or if you have to do it
yourself. Search for other places where SK_ROW_HEADER appears.

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