Re: way to speed up a SELECT DISTINCT?

From: Seth Ladd <seth(at)picklematrix(dot)net>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: way to speed up a SELECT DISTINCT?
Date: 2003-10-10 10:50:48
Message-ID: 9BE142FC-FB0F-11D7-A8D2-000A9576D038@picklematrix.net
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>> Is there any way to speed this up, or is that DISTINCT going to keep
>> hounding me?
>>
>> I checked the mailing list, and didn't see anything like this.
>>
>> Any tips or hints would be greatly appreciated. Thanks for your help!
>> Seth
>>
>>
> Try group by instead. I think this is an old bug its fixed in
> 7.3.2 which I'm using.
>
> Peter Childs
> `
>
>
> peter(at)bernardo:express=# explain select distinct region from region;
> QUERY PLAN
> -----------------------------------------------------------------------
> -----------------------
> Unique (cost=0.00..4326.95 rows=9518 width=14)
> -> Index Scan using regionview_region on region
> (cost=0.00..4089.00
> rows=95183 width=14)
> (2 rows)

Thanks for the tip, I'll give this a shot soon. I am curious, your
example above does not use GROUP BY yet you have an INDEX SCAN. I am
using a similar query, yet I get a full table scan. I wonder how they
are different?

I'll try the group by anyway.

Thanks,
Seth

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