Backup

Backup

SQLiteDatabase.BackupTo wraps SQLite's backup API. It copies the source database into a destination. The source stays open for reads and writes during the copy. If a page changes during the copy, SQLite re-copies it for you.

Backup to another database file

using SQLiteDatabase source = new(new SQLiteOptionsBuilder("app.db").Build());
await source.BackupToAsync("backup.db");

The destination path is opened, written and closed for you. If the file exists, it is overwritten.

Backup to an already-open database

using SQLiteDatabase source = new(new SQLiteOptionsBuilder("app.db").Build());
using SQLiteDatabase destination = new(new SQLiteOptionsBuilder("backup.db").Build());
await source.BackupToAsync(destination);

This overload leaves the destination open after the backup, so you can keep using the copy.

In-memory and file copies

You can load a file into memory at startup for fast reads, then save it back to disk later:

SQLiteDatabase memory = new(new SQLiteOptionsBuilder(":memory:").Build());
SQLiteDatabase file = new(new SQLiteOptionsBuilder("disk.db").Build());

await file.BackupToAsync(memory);

await memory.BackupToAsync(file);

Attached databases

The two optional schema name parameters let you back up an attached database instead of main:

await source.BackupToAsync(destination, sourceName: "aux", destName: "main");

Concurrency

Both the source and the destination connections are locked while the copy runs. Other writes on the source wait until the backup is done. Reads keep working as normal in WAL mode.

VACUUM and VACUUM INTO

Vacuum() rebuilds the database file to reclaim free space and defragment pages. VacuumInto(path) writes a clean copy of the database to a separate file, similar to BackupTo but in a single SQL statement.

await db.VacuumAsync();
await db.VacuumIntoAsync("clean-copy.db");

Pass an attached schema name to operate on that schema instead of main:

await db.AttachDatabaseAsync("aux.db", "aux");
await db.VacuumAsync("aux");
await db.VacuumIntoAsync("aux-copy.db", "aux");

VACUUM cannot run inside a transaction. VACUUM INTO requires SQLite 3.27.0 or newer. Only iOS is affected. It needs iOS 13 or newer. Android always satisfies it because the package bundles its own SQLite there.

VacuumInto is one SQLite statement. The destination file is created fresh and must not already exist. The copy is fully checkpointed and defragmented. BackupTo is incremental, can re-copy pages that change mid-flight and can target an already-open connection.

REINDEX

Reindex() rebuilds indexes. Without an argument, every index in every attached database is rebuilt. Pass a table name to rebuild every index on that table, an index name to rebuild that single index or a collation name to rebuild every index that uses the collation.

await db.ReindexAsync();
await db.ReindexAsync("Books");
await db.ReindexAsync("NOCASE");