> I can imagine a protocol that will improve performance by keeping track
> of whether the database was updated, which would allow a quick
> determination whether a program's cache was still valid. The idea is to
> increment a 'version number' in the database file as soon as a program
> obtains a write lock. A reader could then determine whether the file was
> written to and flush the cache only when necessary, speeding things up a
> little. A 128 bit counter should never wrap around.
Such a counter (32-bits only) was included in the file-format for
version 3. Current versions of the library update the counter every commit,
but it's not being used to allow persistent caches yet. I think such a change
would require a lot of testing before it would be safe enough to use.
And as you say, sophisticated operating systems do a pretty good job of
caching the file anyway.
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