From: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
---|---|
To: | Mark Dilger <pgsql(at)markdilger(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: text_position worst case runtime |
Date: | 2006-05-19 16:20:48 |
Message-ID: | 20060519162046.GZ64371@pervasive.com |
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Thread: | |
Lists: | pgsql-hackers |
On Thu, May 18, 2006 at 06:49:38PM -0700, Mark Dilger wrote:
> > I would think that the worst-case times would be fairly improbable.
> > I'm disinclined to push something as complicated as Boyer-Moore matching
> > into this function without considerable evidence that it's a performance
> > bottleneck for real applications.
>
> A common approach in biological data applications is to store nucleic and amino
> acid sequences as text in a relational database. The smaller alphabet sizes and
> the tendency for redundancy in these sequences increases the likelihood of a
> performance problem. I have solved this problem by writing my own data types
> with their own functions for sequence comparison and alignment, and I used
> boyer-moore for some of that work. Whether the same technique should be used
> for the text and varchar types was unclear to me, hence the question.
Perhaps it would be best to add a seperate set of functions that use
boyer-moore, and reference them in appropriate places in the
documentation. Unless someone has a better idea on how we can find out
what people are actually doing in the field...
--
Jim C. Nasby, Sr. Engineering Consultant jnasby(at)pervasive(dot)com
Pervasive Software http://pervasive.com work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
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