Ok. I can do that. Do I need to keep track of where each pseudo-file open is at, or does sqlite always seek on a file before reading/writing?
Also, do the VFS xLock, etc. functions need to affect the opening or closing of files? That is, if sqlite requests a PENDING or EXCLUSIVE lock on a file and another thread wants to open a connection, do I deny the xOpen call? Or allow the open to succeed, assuming that the future xLock(SHARED) will handle it? Marc -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Richard Hipp Sent: Tuesday, February 07, 2012 3:09 PM To: General Discussion of SQLite Database Subject: Re: [sqlite] File locking requirements in Single Process/Multi-Threaded system On Tue, Feb 7, 2012 at 2:42 PM, Marc L. Allen <[email protected]>wrote: > I'm trying to use sqlite in an embedded, multi-tasking system with a > very simple file system. Essentially, it doesn't support having a file open > multiple times. That is, only one reader or writer. > > I have studied the code, but I can't quite tell how sqlite manages the > DB files in a single process, multi-threaded environment. > > I would like to avoid funneling all DB requests through a single > thread, and maximize concurrency by allowing multiple threads to > access the DB at will. I have some threads that might be doing > relatively long read operations and really don't want to inhibit the > occasional writes. > > Is this possible? Or is OS level file sharing a firm requirement for > multi-threaded operation? > The VFSes for unix and windows both open a separate file descriptor for each database connection. But there is no requirement to do this. For the custom VFS that you have to write to interface to your "very simple file system" you can have all database connections share the same open file connection. > > Thanks, > > Marc > > _______________________________________________ > sqlite-users mailing list > [email protected] > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users > -- D. Richard Hipp [email protected] _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list [email protected] http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
