Re: BUG #14437: BTREE Index is not used for queries on citext columns

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: pawel(dot)kania(at)moneyhouse(dot)de
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #14437: BTREE Index is not used for queries on citext columns
Date: 2016-11-28 16:39:47
Message-ID: 3924.1480351187@sss.pgh.pa.us
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pawel(dot)kania(at)moneyhouse(dot)de writes:
> [ citext LIKE operator isn't indexable ]

Yeah. Don't hold your breath waiting for that to get better :-(.
The problem is that there's no way for extensions to plug into the
"special index operator" mechanism in the planner, so there's no
way to derive indexable range conditions from the citext LIKE operator.
That's probably solvable with enough sweat, but so far no one has
taken an interest in working on it.

Even if that were fixed, I'm not sure that your examples would be
indexable, because the patterns all start with case-foldable characters.
The "special index operator" conversion for ILIKE just throws up its hands
when it sees that, and I doubt citext could do any better.

regards, tom lane

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