On 12/19/2014 11:22 AM, Kushagradhi Bhowmik wrote:
I am writing continuously into a db file which has PRAGMA journal_mode=WAL,
PRAGMA journal_size_limit=0. My C++ program has two threads, one
reader(queries at 15 sec intervals) and one writer(inserts at 5 sec
intervals).
Every 3 min I am pausing insertion to run a sqlite3_wal_checkpoint_v2()
from the writer thread with the mode parameter as
SQLITE_CHECKPOINT_RESTART. To ensure that no active read operations are
going on at this point, I set a flag that checkpointing is about to take
place and wait for reader to complete (the connection is still open) before
running checkpoint. After checkpoint completion I again indicate to readers
it is okay to resume querying.
It shouldn't hurt, but you should not have to manage the readers that
way. SQLITE_CHECKPOINT_RESTART should wait on readers as required to
ensure that the next writer can write into the start of the wal file
instead of appending. If SQLITE_CHECKPOINT_RESTART returns SQLITE_OK,
the next writer should be able to restart the wal file.
If you register an sqlite3_wal_hook() callback it will be invoked to
report the size of the wal file after each write transaction. Logging
this information along with the checkpoint attempts and return codes
might help to shed light on the problem.
Dan.
sqlite3_wal_checkpoint_v2() returns SQLITE_OK, and pnLog and Ckpt as
equal(around 4000), indicating complete wal file has been synced with main
db file. So next write should start from beginning according to
documentation. However, this does not seem to be happening as the
subsequent writes cause the WAL file to grow indefinitely, eventually up to
some GBs.
I did some searching and found that that readers can cause checkpoint
failure due to open transactions. However, the only reader I'm using is
ending its transaction before the checkpoint starts. What else could be
preventing the WAL file from not growing?
___
sqlite-users mailing list
sqlite-users@sqlite.org
http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
___
sqlite-users mailing list
sqlite-users@sqlite.org
http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
