From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | "David E(dot) Wheeler" <david(at)kineticode(dot)com>, Thorbjørn Weidemann <thorbjoern(at)weidemann(dot)name>, "pgsql-hackers(at)postgresql(dot)org Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: citext like searches using index |
Date: | 2013-04-02 14:49:11 |
Message-ID: | 515AEFE7.9010105@gmx.net |
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Lists: | pgsql-hackers |
On 4/2/13 10:26 AM, Tom Lane wrote:
> The issue with the LIKE special case is that left-anchored patterns
> are (to some extent) indexable with ordinary btree indexes, and so we
> want to exploit that rather than tell people they have to have a whole
> other index.
In practice, you need an index specifically for pattern matching anyway.
The difference would be that instead of using a different operator
class that has no recorded association with the original operator, you'd
use a different access method that is associated with the operator in
normal ways.
> So it's a pretty special case, but there are just enough instances of it
> to wish for some not-so-hard-wired way to deal with it.
Are there any widely known non-built-in cases besides citext?
Presumably the reason you use citext is that you use a lot of letters.
So I kind of doubt that there are going to be a lot of cases of pattern
searches on citext with left-anchored patterns starting with (a
sufficient number of) non-letters. It's possible, of course, but
doesn't seem important enough by itself.
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