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());
source.BackupTo("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());
source.BackupTo(destination);

Use this overload when you want to keep using the destination after the backup. For example, to run a check on 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());

file.BackupTo(memory);

memory.BackupTo(file);

Attached databases

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

source.BackupTo(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.

db.Vacuum();
db.VacuumInto("clean-copy.db");

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

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

db.AttachDatabase("aux.db", "aux");
db.Vacuum("aux");
db.VacuumInto("aux-copy.db", "aux");

VACUUM cannot run inside a transaction. VACUUM INTO requires SQLite 3.27.0 or newer; the SQLite.Framework.Bundled package always satisfies that, the OS-provided SQLite needs Android 30 (API level) or iOS 13.

VacuumInto differs from BackupTo in that it is a single SQLite statement, the destination file is created fresh and must not already exist, and 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.

db.Reindex();
db.Reindex("Books");
db.Reindex("NOCASE");

await db.ReindexAsync();