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 Paul www.sandersonforensics.com skype: r3scue193 twitter: @sandersonforens Tel +44 (0)1326 572786 http://sandersonforensics.com/forum/content.php?195-SQLite-Forensic-Toolkit -Forensic Toolkit for SQLite email from a work address for a fully functional demo licence On 20 September 2016 at 08:59, Jose Arroyo <jose.m.arroyo...@gmail.com> 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 ( > https://www.sqlite.org/fileformat.html#wal_index_format). > > 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 > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
