Re: POSIX regex performance bug in 7.3 Vs. 7.2

Well, IMHO I would rather see a delay of the roll-out by a day or two
than see a release with such a serious performance glitch. Especially
since I personally have been shooting my big mouth off to all my geek
friends on the leaps and bounds PG has made in the last few releases. With
my luck one of them will find it. :)
I guess in the end, it comes down to the rest of you developer types, but
I would be inclined to re-wrap. However, this is easy for me to say given
that I have no idea how much work it actually is to re-wrap.
-Wade Klaver

At 08:07 PM 2/3/03 -0500, Tom Lane wrote:
>Sigh. It seems that somebody broke caching of compiled regexes,
>so that your regex is recompiled each time it's used. I haven't
>dug into the logic yet, but I think it must have been a mistake
>in Thomas' change to make the regex cache be searched circularly:
>
>2002-06-14 22:49 thomas
>
> * src/backend/utils/adt/regexp.c: Search the existing regular
> expression cache as a ring buffer. Will optimize the case for
> repeated calls for the same expression, which seems to be the most
> common case. Formerly, always searched from the first entry. May
> want to look at the least-recently-used algorithm to make sure it
> is identifying the right slots to reclaim. Seems silly to do math
> when it seems that we could simply use an incrementing counter...
>
>Considering that we now know that this is a factor-of-150 performance
>hit, I wonder if this is a "must fix" for 7.3.2? We already wrapped
>the tarball, but ...
>
> regards, tom lane
>
>