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Re: WIP: preloading of ispell dictionary

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>, Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: WIP: preloading of ispell dictionary
Date: 2010-03-24 14:41:21
Message-ID: 201003241441.o2OEfMt04925@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Pavel Stehule wrote:
> 2010/3/24 Bruce Momjian <bruce(at)momjian(dot)us>:
> > Pavel Stehule wrote:
> >> 2010/3/24 Craig Ringer <craig(at)postnewspapers(dot)com(dot)au>:
> >> > Pavel Stehule wrote:
> >> >
> >> >> Personally I dislike idea some dictionary precompiler - it is next
> >> >> application for maintaining and maybe not necessary.
> >> >
> >> > That's the sort of thing that can be done when first required by any
> >> > backend and the results saved in a file for other backends to mmap().
> >> > It'd probably want to be opened r/w access-exclusive initially, then
> >> > re-opened read-only access-shared when ready for use.
> >> >
> >> > My only concern would be that the cache would want to be forcibly
> >> > cleared at postmaster start, so that "restart the postmaster" fixes any
> >> > messsed-up-cache issues that might arise (not that they should) without
> >> > people having to go rm'ing in the datadir. Even if Pg never has any bugs
> >> > that result in bad cache files, the file system / bad memory / cosmic
> >> > rays / etc can still mangle a cache file.
> >> >
> >> > BTW, mmap() isn't an issue on Windows:
> >> > ?http://msdn.microsoft.com/en-us/library/aa366556%28VS.85%29.aspx
> >> > It's spelled CreateFileMapping, but otherwise is fairly similar, and is
> >> > perfect for this sort of use.
> >> >
> >> > A shared read-only mapping of processed-and-cached tsearch2 dictionaries
> >> > would save a HUGE amount of memory if many backends were using tsearch2
> >> > at the same time. I'd make a big difference here.
> >> >
> >>
> >> If you know this area well, please, enhance my first patch. I am not
> >> able to oppose to Tom, who has a clean opinion on this patch :(
> >
> > Should we add a TODO?
> 
> why not ?

OK, what would the TODO text be?

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  PG East:  http://www.enterprisedb.com/community/nav-pg-east-2010.do

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Next:From: Tom LaneDate: 2010-03-24 14:46:20
Subject: Re: WIP: preloading of ispell dictionary
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Subject: Re: Performance Improvement for Unique Indexes

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