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feat: add Database#persistWal() to keep the WAL on close - #49
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Add a persistWal([toggleState]) method that sets SQLITE_FCNTL_PERSIST_WAL on the connection's main database. While it is on, the last connection to close still checkpoints the WAL into the database, but keeps the -wal and -shm files instead of deleting them. The next connection then appends to the same WAL with the same salt. This lets zero-cache keep a replica's WAL intact across closes, so a litestream backup can continue from it instead of taking a new snapshot. Today zero-cache does that by holding an extra connection open (WalKeeper). Persistence is off by default, so behavior is unchanged for existing users. It is a no-op for in-memory and temporary databases, and throws if the connection is closed. Turn it off before switching the database out of WAL mode. Otherwise SQLite leaves the -wal file in place and reopens it on the next transaction, so the database effectively stays in WAL mode.
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Add a
persistWal([toggleState])method that setsSQLITE_FCNTL_PERSIST_WALon the connection's main database. While it is on, the last connection to close still checkpoints the WAL into the database, but keeps the -wal and -shm files instead of deleting them. The next connection then appends to the same WAL with the same salt.This lets zero-cache keep a replica's WAL intact across closes, so a litestream backup can continue from it instead of taking a new snapshot. Today zero-cache does that by holding an extra connection open (WalKeeper).
Persistence is off by default, so behavior is unchanged for existing users. It is a no-op for in-memory and temporary databases, and throws if the connection is closed.
Turn it off before switching the database out of WAL mode. Otherwise SQLite leaves the -wal file in place and reopens it on the next transaction, so the database effectively stays in WAL mode.