From: Tom Lane <tgl@sss.pgh.pa.us>
To: Paul Ramsey <pramsey@cleverelephant.ca>
cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: Allowing extensions to supply operator-/function-specific info
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Comments: In-reply-to Paul Ramsey <pramsey@cleverelephant.ca>
	message dated "Mon, 25 Feb 2019 15:39:49 -0800"
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Date: Mon, 25 Feb 2019 19:09:11 -0500
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Paul Ramsey <pramsey@cleverelephant.ca> writes:
> On Mon, Feb 25, 2019 at 3:01 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> It's whichever one the index column's opclass belongs to.  Basically what
>> you're trying to do here is verify whether the index will support the
>> optimization you want to perform.

> * If I have tbl1.geom
> * and I have built two indexes on it, a btree_geometry_ops and a
> gist_geometry_ops_2d, and
> * and SupportRequestIndexCondition.opfamily returns me the btree family
> * and I look and see, "damn there is no && operator in there"
> * am I SOL, even though an appropriate index does exist?

No.  If there are two indexes matching your function's argument, you'll
get a separate call for each index.  The support function is only
responsible for thinking about one index at a time and seeing if it
can be used.  If more than one can be used, figuring out which
one is better is done by later cost comparisons.

			regards, tom lane