From within SQLite - I don't know if its possible.

But if you can query the WAL file size you should be able to determine
the number of pages easily enough.

pages = (walfilesize-32)/(DBpagesize+24)

the only caveats I can think of are:

The WAL file is not truncated after a checkpoint so you would need to
make sure your checkpoint was done in truncate mode:

PRAGMA wal_checkpoint(truncate)

WAL auto checkpoints are always passive so you would need to disable
autocheckpointing and do all checkpoints yourself manually as above to
ensure WAL is truncated.

PRAGAM wal_autocheckpoint = 0

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On 20 September 2016 at 08:59, Jose Arroyo <> wrote:
> From looking at the source code, it seems to me that the values returned
> on wal_hooks come from some sqlite's internal variables so it doesn't seem
> to be possible to query the DB for it. I suspect that the WAL size can be
> calculated from the WAL index file somehow, but I don't really grok how it
> is actually used from the docs online (
> My current issue is that I'm encountering WAL checkpoint starvation and I'm
> trying to figure out a way to create checkpoint gaps only when needed. The
> scenario is pretty standard, one writer process and several readers
> processes. The writer notifies the readers in some specific DB updates
> scenarios, the readers query, do some stuff, update some fields by
> messaging the writer process who will queue up those updates. After a
> certain DB size, checkpoints start failing more and more often to the point
> that the WAL size starts growing unbounded.
> The caveat is that all this happens under a SPARQL layer and that I don't
> have much room to modify how the writer process works. So I was wondering
> if I could access the current number of pages in the WAL from outside the
> writer process in a cheap way.
> Any advice or guidance is greatly appreciated
> Cheers,
> José M. Arroyo
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