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Date: Sat, 1 Jun 2013 12:58:13 +0200
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: sqlite3: bug with monotone
Message-ID: <20130601105813.GD30659@calimero.vinschen.de>
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References: <51A6B6EB.6050309@users.sourceforge.net> <loom.20130530T122354-144@post.gmane.org> <51A7862F.1070507@etr-usa.com> <51A7D47E.3050502@users.sourceforge.net> <51A7F547.6020509@etr-usa.com> <20130531092228.GB30659@calimero.vinschen.de> <51A900EF.2020606@etr-usa.com> <51A905DC.6020109@etr-usa.com>
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User-Agent: Mutt/1.5.21 (2010-09-15)

On May 31 14:19, Warren Young wrote:
> On 5/31/2013 13:58, Warren Young wrote:
> >
> >The SQLite code prefers POSIX advisory locks, but it can fall back to
> >BSD locks if it has to.
> 
> Just to clarify, when I say "POSIX locks" I always mean new style
> fcntl() locks.  There are no calls to lockf() in sqlite3.c.
> 
> >I'm not sure why it doesn't just
> >blindly try the lock.
> 
> On reflection, I'm sure it has something to do with maintaining high
> concurrency.  If it knows its near-future DB file write is going to
> get blocked, it can choose to do something else while the existing
> DB lock holders finish.
> 
> By contrast, SQLite's flock() based locking is documented as being
> much more brute-force, resulting in much lower concurrency.

Makes sense, given that flock is not record but file locking.


Corinna

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Corinna Vinschen                  Please, send mails regarding Cygwin to
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