From: | Erik Jones <erik(at)myemma(dot)com> |
---|---|
To: | Postgres User <postgres(dot)developer(at)gmail(dot)com> |
Cc: | pgsql-general <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Regex query not using index |
Date: | 2008-02-20 04:45:41 |
Message-ID: | F933830E-FDA5-4889-92EB-2301DC49E6DF@myemma.com |
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Thread: | |
Lists: | pgsql-general |
On Feb 19, 2008, at 9:32 PM, Postgres User wrote:
> I'm running a simple query on 8.2. With this syntax, Explain indicate
> that the index is scanned:
> select * from eod where name = 'AA'
>
> However, when I change the query to use simple regex:
> select * from eod where name ~ 'AA'
>
> now Explain indicates a seq scan:
> Index Scan using equity_eod_symbol_idx on equity_eod (cost=0.00..8.27
> rows=1 width=149)
> Index Cond: ((symbol)::text = 'AA'::text)
>
> Is there any way to 'encourage' Postgres to hit the index when using
> regex? Do I need to create a functional index or something?
> Without the index in play, I really can't use regex on any of my
> larger tables.
You need it to be anchored:
select * from eod where name ~ '^AA';
If you're looking to be able to use indexes for searches within a
string then, for 8.2, you'll need to check out tsearch2.
Erik Jones
DBA | Emma®
erik(at)myemma(dot)com
800.595.4401 or 615.292.5888
615.292.0777 (fax)
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