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Re: WIP: index support for regexp search

From: Alexander Korotkov <aekorotkov(at)gmail(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: index support for regexp search
Date: 2012-01-19 20:54:24
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Lists: pgsql-hackers
On Fri, Jan 20, 2012 at 12:30 AM, Heikki Linnakangas <
heikki(dot)linnakangas(at)enterprisedb(dot)com> wrote:

> The code badly needs comments. There is no explanation of how the trigram
>> extraction code in trgm_regexp.c works.
> Sure. I hoped to find a time for comments before commitfest starts.
Unfortunately I didn't, sorry.

> Guessing from the variable names, it seems to be some sort of a coloring
> algorithm that works on a graph, but that all needs to be explained. Can
> this algorithm be found somewhere in literature, perhaps? A link to a paper
> would be nice.
I hope it's truly novel. At least application to regular expressions. I'm
going to write a paper about it.

> Apart from that, the multibyte issue seems like the big one. Any way
> around that?

Conversion of pg_wchar to multibyte character is the only way I found to
avoid serious hacking of existing regexp code. Do you think additional
function in pg_wchar_tbl which converts pg_wchar back to multibyte
character is possible solution?

With best regards,
Alexander Korotkov.

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