On 21-Feb-05, at 10:39 AM, [EMAIL PROTECTED] wrote:It is a trade off between guaranteed data integrity and performance. If there happen to be a bunch of other apps writing to the disk when you do a SQLite transaction, then all of that data has to be flushed to the disk. As Domnic said, fsync() does not guarantee that the bytes hit the platter on any system. Pull the plug after a COMMIT and you are very likely going to see only part of the pages written.
You can also use the 'synchronous' pragma to control the number of F_FULLSYNCs executed during any single transaction. By default, it will be three-- probably too excessive.
I sill want the "normal" fsync() called and using this pragma means fsync() is not called.
OK -- so, you are willing to accept the risk of non-recoverable database corruption in the event of power outage or other kinds of catastrophic system failure (including the plug being pulled on a FireWire drive without it being properly unmounted)?
I.e. that risk is perceived to be acceptably small that the performance hit is not justifiable?
The best way to guarantee maximal performance is to bunch up your INSERT and UPDATE statements into transactions as much as possible. This is often true regardless of the presence of F_FULLSYNC.
My application does this and the performance was still very poor on OS X with F_FULLSYNC on. Since OS X is the only OS which has F_FULLFSYNC it would be nice to make the use of it a configure option.
Noted. Thanks.
b.bum
