SqLite 数据库在 unicode 和 PRAGMA journal_mode 设置时不会关闭

Question

My windows application (written in C) uses SQLite (using the embedded amalgamated source) for storing offline data, and have had no problems with it in a multibyte character set build. I'm now converting the codebase to Unicode. SQLite is quite happily running with the Unicode build, creating SQLite databases in UTF-16LE encoding.

I've come across one very odd thing, though. If I run the query PRAGMA journal_mode = DELETE (actually, setting it to ANY of the allowed values, including OFF , does the same thing), everything runs fine until the code closes the database, at which point the call to sqlite3_close() returns SQLITE_BUSY , with the error "unable to close due to unfinalised statements" .

This happens even if the only query I run on the database is that single pragma command. I can run other pragmas fine (eg "PRAGMA synchronous = NORMAL" ) and all my SQL queries, and the database will close quite happily; it's just this journal_mode pragma that's causing this odd behaviour, and ONLY in the Unicode build of the code - the multibyte build doesn't show this problem. This happens whether the database exists already [in UTF-16LE mode], or whether it creates it on first opening.

Any ideas what could be wrong? I'm using SQLite build v3.7.11.

Answer 1

I found the problem in the end. Was in my own wrapper code. As sqlite has no unicode equivalent call for sqlite3_exec() , I had let the unicode version drop through to my code that does prepare/step/finalize (for when the caller wants data back from an SQL query), but for some reason setting the journal_mode pragma causes SqLite to return some data, which it doesn't for the other pragmas I set - thus there was an unfinalised stmt for just this pragma.

For future reference, if you get SQLITE_BUSY when closing, you can call sqlite3_next_stmt() to get the [next] unfinalised statement, then sqlite3_sql() to get it to tell you the prepared SQL statement associated with it. Very useful!