Re[2]: [Exim] exim's databases and sql

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Author: Richard Welty
Date:  
To: exim-users
Subject: Re[2]: [Exim] exim's databases and sql
On Mon, 6 Oct 2003 19:36:51 +0200 Mark Bergsma <mark@???> wrote:
> Are you sure about this? I find that hard to believe. The web page talks
> about
> 'atomic commit and rollback', and I can't find anything on it that
> supports
> your claim, not even on the 'unsupported features' page.


i was 1/2 right (and 1/2 wrong.) locking is in question 7 of the SQLite
FAQ,

http://www.hwaci.com/sw/sqlite/faq.html#q7

a particularly relevant quote from that faq:

"Locking in SQLite is very course-grained. SQLite locks the entire
database. Big database servers (PostgreSQL, Oracle, etc.) generally
have finer grained locking, such as locking on a single table or a
single row within a table. If you have a massively parallel database
application, you should consider using a big database server instead
of SQLite."

there's rather a lot more detail in the faq answer. to summarize, SQLite
locking is extremely weak. in particular, SQLite shouldn't be run on NFS
files systems for all the usual file locking reasons.

so as i suggested, big web sites using PHP w/SQLite may have some serious
issues to deal with under heavy load. this isn't going to be pretty...

richard
--
Richard Welty                                         rwelty@???
Averill Park Networking                                         518-573-7592
    Java, PHP, PostgreSQL, Unix, Linux, IP Network Engineering, Security