> If you have one reader and many writers, consider PRAGMA journal_mode=WAL;
Richard meant "one writer and many readers" of course. >> If the other process opens the db connection as read_only, will the hot >> journal check be still done (during queries operations of the second >> process)? >> > > How is the second process suppose to know whether or not the other process > used read_only? And even those who opened db connection as read_only will check for hot journal before executing any query. Pavel On Wed, Aug 10, 2011 at 1:44 PM, Richard Hipp <d...@sqlite.org> wrote: > On Wed, Aug 10, 2011 at 1:35 PM, Sreekumar TP <sreekumar...@gmail.com>wrote: > >> Ok, its getting a bit clear. >> If there is only one process that is writing to the database, but has more >> than one process that reads the database, the locking mode can still be >> exclusive ? >> > > PRAGMA locking_mode=EXCLUSIVE; means "exclusive'. Only one process can > access. > > If you have one reader and many writers, consider PRAGMA journal_mode=WAL; > > > >> If the other process opens the db connection as read_only, will the hot >> journal check be still done (during queries operations of the second >> process)? >> > > How is the second process suppose to know whether or not the other process > used read_only? > > >> >> >> >> >> On Wed, Aug 10, 2011 at 10:54 PM, Richard Hipp <d...@sqlite.org> wrote: >> >> > On Wed, Aug 10, 2011 at 1:09 PM, Simon Slavin <slav...@bigfraud.org> >> > wrote: >> > >> > > >> > > On 10 Aug 2011, at 6:01pm, Sreekumar TP wrote: >> > > >> > > > Thanks for the explanation. The journal mode was OFF which means >> there >> > > is >> > > > no journal file created. So why is it the check still performed ? >> > > >> > > Because the journal mode might have been 'ON' the last time that >> > database >> > > was used. >> > > >> > >> > More importantly, the journal mode might be 'ON' in the other process >> that >> > crashed in the middle of a transaction. >> > >> > >> > >> > > >> > > > On Wed, Aug 10, 2011 at 10:24 PM, Richard Hipp <d...@sqlite.org> >> wrote: >> > > > >> > > >> On Wed, Aug 10, 2011 at 12:40 PM, Sreekumar TP < >> > sreekumar...@gmail.com >> > > >>> wrote: >> > > >> >> > > >>> The 179148 failures on 'access' system call is due to access check >> of >> > > two >> > > >>> files - the journal file and the wal-file. >> > > >> > > Well, the file is obviously not being opened 179148 times. I thought >> it >> > > checked for these files only when sqlite3_open() was being run. Is it >> > > checking for these files every time a command is executed ? Surely >> that >> > is >> > > unnecessary and a source of a large reduction in speed. >> > > >> > >> > SQLite must check for hot journals at the start of each transaction. >> > >> > Or, more precisely, SQLite must check for hot journals whenever it starts >> > reading the database again after a period of time when another process >> > might >> > have been writing to the database (and might have crashed while writing). >> > >> > That's when PRAGMA locking_mode=EXCLUSIVE blocks the hot-journal checks. >> > If >> > your process has exclusive access to the database, it is not possible for >> > another process to write to the database (and crash in the middle of >> > writing). >> > >> > >> > >> > > >> > > Simon. >> > > _______________________________________________ >> > > sqlite-users mailing list >> > > sqlite-users@sqlite.org >> > > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >> > > >> > >> > >> > >> > -- >> > D. Richard Hipp >> > d...@sqlite.org >> > _______________________________________________ >> > 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 >> > > > > -- > D. Richard Hipp > d...@sqlite.org > _______________________________________________ > 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
