Support sqlite3_file_control()

[benbjohnson]

Hi @mattn, thanks for the great library. I use it all the time.

I'm using go-sqlite3 in my Litestream project for SQLite replication and I've been doing a hack to persist the WAL file across restarts where I just don't call Close() on the database. Definitely hacky but it works. However, I recently learned there's sqlite3_file_control() opcode called SQLITE_FCNTL_PERSIST_WAL that does the same thing.

Is there an existing way to execute sqlite3_file_control() in go-sqlite3? I didn't see one but I thought I'd ask.

I'm happy to add the functionality. Are you open to accepting a patch for it?

[rittneje]

Seems fine. But do be mindful that some users compile against their system installation of SQLite, meaning that not all constants/functions from the statically compiled header file are guaranteed to exist in all cases.

[benbjohnson]

@rittneje I pushed up a pull request to add a FileControl() method to SQLiteConn and a corresponding test. I also tested it against Litestream in this persist-wal branch. Let me know if there's anything you'd like me to change with the PR. Thanks!