Horton

Re: WIP: index support for regexp search

Alexander Korotkov <aekorotkov@gmail.com>

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From: Alexander Korotkov <aekorotkov@gmail.com>
To: Erik Rijkers <er@xs4all.nl>
Cc: Heikki Linnakangas <hlinnakangas@vmware.com>, Tom Lane <tgl@sss.pgh.pa.us>, Tomas Vondra <tv@fuzzy.cz>, pgsql-hackers@postgresql.org, pavel.stehule@gmail.com
Date: 2012-12-18T09:10:00Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Fix filling of postmaster.pid in bootstrap/standalone mode.

  2. Add explicit casts in ilist.h's inline functions.

On Tue, Dec 18, 2012 at 12:51 PM, Erik Rijkers <er@xs4all.nl> wrote:

> On Tue, December 18, 2012 09:45, Alexander Korotkov wrote:
> >
> > You should use {0,n} to express from 0 to n occurences.
> >
>
>
> Thanks, but I know that of course.  It's a testing program; and in the end
> robustness with
> unexpected or even wrong input is as important as performance.  (to put it
> bluntly, I am also
> trying to get your patch to fall over ;-))
>

I found most of regressions in 0.9 version to be in {,n} cases. New version
of patch use more of trigrams than previous versions.
For example for regex 'x[aeiou]{,2}q'.
In 0.7 version we use trigrams '__2', '_2_' and '__q'.
In 0.9 version we use trigrams 'xa_', 'xe_', 'xi_', 'xo_', 'xu_', '__2',
'_2_' and '__q'.

But, actually trigram '__2' or '_2_' never occurs. It enough to have one of
them, all others are just causing a slowdown. Simultaneously, we can't
decide reasonably which trigrams to use without knowing their frequencies.
For example, if trigrams 'xa_', 'xe_', 'xi_', 'xo_', 'xu_' were altogether
more rare than '__2', newer version of patch would be faster.


------
With best regards,
Alexander Korotkov.