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Re: sqlite3: bug with monotone
- From: Corinna Vinschen <corinna-cygwin at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Sat, 1 Jun 2013 12:58:13 +0200
- Subject: Re: sqlite3: bug with monotone
- References: <51A6B6EB dot 6050309 at users dot sourceforge dot net> <loom dot 20130530T122354-144 at post dot gmane dot org> <51A7862F dot 1070507 at etr-usa dot com> <51A7D47E dot 3050502 at users dot sourceforge dot net> <51A7F547 dot 6020509 at etr-usa dot com> <20130531092228 dot GB30659 at calimero dot vinschen dot de> <51A900EF dot 2020606 at etr-usa dot com> <51A905DC dot 6020109 at etr-usa dot com>
- Reply-to: cygwin at cygwin dot com
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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