On 2015-11-25 22:19, Peter Haworth wrote:
Maybe I'm missing something but I don't understand why the issue of
concurrent users keeps coming up in threads about SQL dbs. There are
perfectly good mechanisms built into every SQL implementation to
preserve
the integrity of the db, that's ACID is all about, or at least the "I"
in
it. They require that correct programming techniques are used of
course,
but without concurrency control, an SQL db would be pretty much
useless.
SQLite is designed as a single-file database to be mutated by a single
process.
The ability to have multiple processes write to the same database file
has nothing to do with ACID compliance - in order for that to be
possible, the operating system would have to provide strong guarantees
on file locking which none do in all situations (UNIX based systems, for
example, tend to only have advisory locks, not guaranteed locks meaning
that processes have to co-operate).
Indeed, an SQLite database is perhaps not really any different from the
data files you point a MySQL, or PostgreSQL instance at. I'd suspect
they would get really screwed up if you tried to run two servers
pointing at the same files and, indeed, that isn't how they are meant to
be used as the point of using a 'database server' is to allow concurrent
multi-user access. Of course you could write an database server which
uses SQLite as the datastore (some have!) - but that is a distinctly
different use-case for which SQLite is intended for in terms of 'direct
access'.
Warmest Regards,
Mark.
--
Mark Waddingham ~ m...@livecode.com ~ http://www.livecode.com/
LiveCode: Everyone can create apps
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