Question

I need a very fast SQLite database acces. Setting parameters this way:

PRAGMA synchronize = OFF
PRAGMA jorunal_mode = MEMORY

makes the speed to be enough for my project.
These settings makes SQLite to leave synchronization with database file in the hands of operating system.
But there are a few cases, some certain inserts, after which I must be sure that the data was written to the disk.

Is there any way I can force SQLite to write all data (waiting in memory journal) to disk?

Thanks.

Answer 1

I would suggest you use the recently implemented WAL journal_mode. This way, you can leave synchronous to normal and have all your writes written to disk as you go:

Write transactions are very fast since they only involve writing the
content once (versus twice for rollback-journal transactions) and
because the writes are all sequential. Further, syncing the content to
the disk is not required, as long as the application is willing to
sacrifice durability following a power loss or hard reboot. (Writers
sync the WAL on every transaction commit if PRAGMA synchronous is set
to FULL but omit this sync if PRAGMA synchronous is set to NORMAL.)

The above is taken from:

http://www.sqlite.org/wal.html

If that is not enough, you can still then invoke PRAGMA database.wal_checkpoint; when you want to be certain that your writes are not only written to disk, but also “integrated” to your DB. Check the following for more information:

http://www.sqlite.org/pragma.html#pragma_wal_checkpoint