From: | Richard Yen <dba(at)richyen(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: query plan with index having a btrim is different for strings of different length |
Date: | 2008-12-11 01:44:23 |
Message-ID: | 3EF5395F-0F95-4313-B64A-ECAAE2880C57@richyen.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-performance |
On Dec 10, 2008, at 4:08 PM, Tom Lane wrote:
> Richard Yen <dba(at)richyen(dot)com> writes:
>> Is there any way to tune this so that for the common last names,
>> the query
>> run time doesn't jump from <1s to >300s?
>
> Well, as near as I can tell there's factor of a couple hundred
> difference between the frequencies of 'smith' and 'smithers', so
> you shouldn't really expect similar runtimes for the two cases.
>
> Having said that, I still think you should try to index both first
> and last name. Also I wonder whether the index on owner is worth
> having at all. It definitely doesn't seem worthwhile to index the
> entries with owner = -1, since there are so many; so maybe you could
> make it a partial index that excludes those entries, in order to
> prevent
> the planner from trying to use it for this case.
Created the 2-col index, and the query runs much faster on all
permutations.
Thanks much for all your help,
--Richard
From | Date | Subject | |
---|---|---|---|
Next Message | Matthew Wakeling | 2008-12-11 13:47:19 | Re: Experience with HP Smart Array P400 and SATA drives? |
Previous Message | Tom Lane | 2008-12-11 00:08:28 | Re: query plan with index having a btrim is different for strings of different length |