Hi! Can you help me understand more exactly what the output parameters
are from sqlite3_wal_checkpoint_v2()? Specifically:
1) What is the relationship between pnLog and pnCkpt: is pnLog>=pnCkpt
always true?
2) Under what circumstances would pnLog>pnCkpt be true?
Also, can you confirm I understand the following correctly:
3) When using SQLITE_CHECKPOINT_PASSIVE, the WAL file will grow as
needed, indefinitely, without ever shrinking.
4) When using a separate checkpointing thread, pnLog only goes down if
the read/write thread has no active queries when the checkpoint runs.
(Eg, if the checkpoint thread runs while the read/write thread has an
active query, it'll still checkpoint, but it just won't reset the pnLog
to 0.)
Finally, and I'm not sure if this is related, but I've read in several
threads that sometimes you can get the SQLITE_CORRUPT error even if the
database isn't corrupt, and the proper response is to just retry.
5) Is this considered to be a bug, or is it the result of some temporary
hardware issue?
6) Is this aggravated by the use of WAL, or totally unrelated?
Some data about our setup is at the end of this email; I welcome you
advice. Thanks!
-david
----------------------------------------------------------------------
We have a 3.7.7.1 database named "main.db", which is in WAL mode, with a
corresponding "main.db-wal" file. The main.db file is 13519440896 bytes
(about 13GB) while the WAL file is 25439184 bytes (about 25MB). Both
threads open the database with "SQLITE_OPEN_READWRITE |
SQLITE_OPEN_CREATE | SQLITE_OPEN_NOMUTEX" and SQLITE_CONFIG_MULTITHREAD,
sqlite3_enable_shared_cache(0), and set "PRAGMA journal_mode = WAL;" We
checkpoint the main.db database every 15 seconds using
SQLITE_CHECKPOINT_PASSIVE, outputting pnLog and pnChkpt each time, with
the results looking something like:
298 298
263 263
483 483
943 943
1171 1171
1653 1653
1947 1947
212 212
436 436
1011 1011
1277 1277
1611 1611
2035 2035
2408 2408
2703 2703
3128 3128
548 548
858 858
1338 1338
1839 1839
386 386
493 493
679 679
_______________________________________________
sqlite-users mailing list
[email protected]
http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
