Yes. If you are starting a transaction in which you know you are going to write use BEGIN IMMEDIATE. Plain BEGIN (BEGIN DEFERRED) starts a READ transaction and only attempts to upgrade to a write transaction when you try to write. Since a read transaction in WAL works with a version of the data that is current at the time the transaction is started, then you cannot upgrade an "old snapshot" for reading to writing (since it cannot "see: the changes being made by the in-process transaction).
--- The fact that there's a Highway to Hell but only a Stairway to Heaven says a lot about anticipated traffic volume. >-----Original Message----- >From: sqlite-users [mailto:sqlite-users- >boun...@mailinglists.sqlite.org] On Behalf Of Nick >Sent: Tuesday, 13 February, 2018 23:19 >To: sqlite-users@mailinglists.sqlite.org >Subject: Re: [sqlite] Question about threadsafe > >>> So I think "threadsafe=2 + more than 1 connection + busy_handler" >is a >good >>> way to use. > >>This is the normal way to use SQLite. > >I ran a test and I can still find "database is locked" even if I use >busy_handler(threadsafe=2, 2 connections). >When thread 1 executing a writing transaction, thread 2 runs the code >below >at the same time: >sqlite3_exec("BEGIN") >//SELECT >sqlite3_prepare_v2("SELECT * FROM t1;"); >sqlite3_step; >sqlite3_reset; >//INSERT >sqlite3_exec("INSERT INTO t1 VALUES(1, 1, \"aweagsr\")");//database >is >locked >sqlite3_exec("COMMIT"); > >Writing in thread 1 will no block SELECTs in thread 2 as I use WAL. >But the >INSERT within the transaction of thread 2 still returns SQLITE_BUSY. >I think I have used sqlite3_busy_timeout() in right way and I find >that >sqliteDefaultBusyCallback() did not be called. > >Is it expected? > > > > >-- >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 _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
