[EMAIL PROTECTED] wrote:
This presented itself with the following scenario:
- sqlite_open() some unimportant database file
- set PRAGMA SYNCHRONOUS=OFF
- do some things that cause pPg->needSync to be true for some set of pages.
this will also have set pPager->needSync to be true.
- ATTACH some more important database file
- set PRAGMA SYNCHRONOUS=ON because now data integrity is important
When sqlitepager_commit() is later called, it will fail the assert because
sqlitepager_set_cachesize() which re-enabled synchronous mode, reset the pager
structure's needSync (pPager->needSync = 0) but did not actually flush the
pages to the journal (i.e. pPager->pAll->needSync is still 1).
Thanks for tracking this down.
I have not analyzed this situation closely. But I wonder if a
simpler (and safer) solution to this problem would be to disallow
the changing of PRAGMA SYNCHRONOUS in the middle of a transaction?
Am I correct in understanding that the problem only occurs if
you do something like this:
PRAGMA synchronous=off;
BEGIN;
-- do some things
PRAGMA synchronous=on;
-- possibly do other things
COMMIT;
Changing the synchronous setting in the middle of a transaction
seems dubious and risky to me. Your patch may well fix the immediate
problem but I worry that there may be other undetected problems that
remain unresolved. Disallowing a synchronous change in the middle
of a transaction seems to be both safer and easier. Or am I not
understanding the problem correctly?
--
D. Richard Hipp -- [EMAIL PROTECTED] -- 704.948.4565
