GRDB request.deleteAllOther(db)

GRDB+DeleteAllOther.swift

import GRDB

extension QueryInterfaceRequest where RowDecoder: MutablePersistableRecord {
    /// Deletes all records in the database, but the ones selected by the request.
    ///
    /// For example:
    ///
    ///     // Delete all players whose score is below 1000
    ///     let bestPlayers = Player.filter(Column("score") > 1000)
    ///     try dbQueue.write(bestPlayers.deleteAllOther)
    ///
    /// - parameter db: A database connection.
    /// - returns: The number of deleted rows.
    @discardableResult
    func deleteAllOther(_ db: Database) throws -> Int {
        try db.execute(literal: """
            DELETE FROM \(RowDecoder.self) WHERE \(RowDecoder.primaryKey) NOT IN (\(select(RowDecoder.primaryKey)))
            """)
        return db.changesCount
    }
}