On Fri, 2 Dec 2005, C C wrote:
>On 12/2/05, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>> The added risk in going from synchronous=FULL to synchronous=NORMAL
>> is minimal. You only run into trouble [when] you select
>> synchronous=OFF.
>
>you've piqued my interest... Does sqlite implement MVCC (multiversion
>concurrency)?
No.
Might be an interesting addition, but locking of the btree structure would
be difficult to make performant, as communication of locking is via file
locks only. MVCC works very well on centralised servers because locks are
short lived and can be quickly communicated using regular IPC.
It might be feasable to have intra-process MVCC on a single SQLite
database with multiple handles, but inter-process MVCC would be
problematic, as is scheduling vacuuming of stale data. It could, however,
remove the limit that a writer cannot commit until all readers are
finished, so improving concurrency somewhat.
Basically, it'd be too complex (IMHO) to implement in a 'lite' database
engine.
>
>-cc
>
Christian
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