Re: Slow select times on select with xpath

From: Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>
To: astro77 <astro_coder(at)yahoo(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Slow select times on select with xpath
Date: 2009-09-22 05:12:30
Message-ID: 4AB85CBE.4020803@cheapcomplexdevices.com
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astro77 wrote:
> Thanks Kevin. I thought about using tsearch2 but I need to be able to select
> exact values on other numerical queries and cannot use "contains" queries.

You might be able to make use of a custom parser for tsearch2 that creates
something like a single "word" for xml fragments like <whatever>1</whatever>
which would let you quickly find exact matches for those words/phrases.

> It's got to be fast so I cannot have lots of records returned and have to do
> secondary processing on the xml for the records which contain the exact
> value I'm looking for. This is one of the reasons I moved from using Lucene
> for searching. I hope this makes sense.
>
>
> Kevin Grittner wrote:
>> wrote:
>>
>>
>> I would try to minimize how many XML values it had to read, parse, and
>> search. The best approach that comes to mind would be to use tsearch2
>> techniques (with a GIN or GiST index on the tsvector) to identify
>> which rows contain 'fdc3da1f-060f-4c34-9c30-d9334d9272ae', and use AND
>> to combine that with your xpath search.
>>
>> -Kevin
>>
>>
>>
>

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