Thanks, Simon, perhaps I did not formulate may question clearly enough. The class of course works as you wrote, the only problem relates to the error handling.
If you are interested, the C# wrapper (original code) is here <https://raw.githubusercontent.com/OpenDataSpace/System.Data.SQLite/master/System.Data.SQLite/SQLite3.cs> . (UnsafeNativeMethods class contains a collection of function pointers to sqlite3.dll.) This is the part of the code I want to discuss (a shortened version): <code> internal override bool Step(SQLiteStatement stmt) { Random rnd = new Random(); uint starttick = (uint)Environment.TickCount; uint timeout = (uint)(stmt._command._commandTimeout * 1000); while (true) { SQLiteErrorCode n = UnsafeNativeMethods.sqlite3_step(stmt._sqlite_stmt); if (n == SQLiteErrorCode.Row) return true; if (n == SQLiteErrorCode.Done) return false; if (n != SQLiteErrorCode.Ok) //*) { SQLiteErrorCode r = Reset(stmt); if (r == SQLiteErrorCode.Ok) throw new SQLiteException(n, GetLastError()); // Only Locked/Busy err code can pass here if ((uint)Environment.TickCount - starttick > timeout) throw new SQLiteException(r, GetLastError()); System.Threading.Thread.Sleep(rnd.Next(1, 150)); } } } internal override SQLiteErrorCode Reset(SQLiteStatement stmt) { SQLiteErrorCode n = UnsafeNativeMethods.sqlite3_reset(stmt._sqlite_stmt); if (n == SQLiteErrorCode.Locked || n == SQLiteErrorCode.Busy || n == SQLiteErrorCode.Ok) return n; throw new SQLiteException(n, GetLastError()); } </code> *) STRANGE: 1) SQLITE_OK should not happen. (Official documentation allows /ANY/ result code. I hope this not true.) 2) If it happens, then this looks dangerous. I don't like a lot of things about the C# wrapper (heavy overhead, SQL_SCHEMA dealing, timeouts...). But those points are not crucial. What I ask is following: a) If sqlite3_step() returns error code different from 100/101, should we call sqlite3_reset()? This looks like a bug to me. (Imagine we are reading a table.) b) If we get Locked/Busy errors, is it safe and reasonable to retry sqlite3_step? Note that if we solve this way some multi-access conflicts, then this is a welcome feature. Meanwhile I collected more info about the problem. First, a reduced version of the sqlite3_step() official documentation that applies to these conditions: - Sqlite 3.7.15, SQLITE_OMIT_AUTORESET was not defined - The statement was prepared using sqlite3_prepare_v2() / sqlite3_step returns SQLITE_BUSY, SQLITE_DONE, SQLITE_ROW, SQLITE_ERROR, SQLITE_MISUSE, or any other result code SQLITE_ROW/SQLITE_DONE... (description omitted) SQLITE_BUSY means a failure to acquire a DB lock. If the statement is a COMMIT or occurs outside of an explicit transaction, then you can retry the statement. Otherwise you should rollback. SQLITE_ERROR means a run-time error. sqlite3_step() should not be called, sqlite3_errmsg() provides additional info. SQLITE_MISUSE means that this routine was called inappropriately, such as on a finalized statement. If sqlite3_step() returns anything other than SQLITE_ROW, then the next call to sqlite3_step() automatically calls sqlite3_reset(). / Another SQLite document says <http://www.sqlite.org/unlock_notify.html> "/SQLITE_LOCKED error may only occur on the first call to sqlite3_step()/". And Mr. Hipp <http://sqlite.1065341.n5.nabble.com/Questions-about-VDBE-deadlocks-and-SQLITE-BUSY-tp1025p1026.html> seems to have confirmed the same for SQLITE_BUSY. (Although 10 years ago) Dan Kennedy says <http://sqlite.1065341.n5.nabble.com/shared-cache-and-SQLITE-MISUSE-on-sqlite3-step-tp47214p47232.html> "/After SQLITE_BUSY is returned, you can call sqlite3_step() again immediately/". (Note that this is not the same as the official documentation says.) Knowing now above info, I don't see the C# wrapper code that bad as yesterday, though I am still far from being sure that it is 100% ok. -- View this message in context: http://sqlite.1065341.n5.nabble.com/sqlite3-step-and-SQLITE-LOCKED-BUSY-tp77690p77707.html Sent from the SQLite mailing list archive at Nabble.com. _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
