I ran several multi-threads tests these days and I want to get a confirmation that my understanding is correct. I use WAL mode and I think whether or not use the same connection with THREADSAFE=1, 2 is the key to my question.
Mode 1, threadsafe=2 + multiple threads use the same connection: It is not threadsafe; Mode 2, threadsafe=2 + each thread runs a sqlite3_open(): It is threadsafe which means reading and writing can proceed concurrently, but only one writer at a time. PRAGMA busy_timeout() may avoid “db is locked” when writing. Mode 3, threadsafe=1 + each thread runs a sqlite3_open(): Same with mode 2, as threadsafe=1 is only supported the ability of a handle to be used by more than one thread. Mode 4, threadsafe=1 + multiple threads use the same connection: Reading and writing can proceed concurrently; Two writers can start at the same time and sqlite will make them Serialized(but how? guess some threads will be blocked and retry, but I can not find it in the source code). In general, WAL make reading and writing concurrent - not just serial, but writing and writing can only be serial. So writers should use busy_timeout() to retry(Mode 2), or, use the same connection and the RETRY operation will be done by sqlite(Mode 4). I think sqlite is threadsafe means the integrity of database is guaranteed. And there will not be any crash or corruption if applications use sqlite the way like mode 2 and 4 above. Is it right? Thanks. -- Sent from: http://sqlite.1065341.n5.nabble.com/ _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
