108 lines
4.9 KiB
Swift
108 lines
4.9 KiB
Swift
import Foundation
|
|
|
|
/// Represents the journal modes available for an SQLite database.
|
|
///
|
|
/// The journal mode determines how the database handles transactions and how it maintains the
|
|
/// journal for rollback and recovery.
|
|
///
|
|
/// - SeeAlso: [journal_mode](https://sqlite.org/pragma.html#pragma_journal_mode)
|
|
public enum JournalMode: String, SQLiteRepresentable {
|
|
/// DELETE journal mode.
|
|
///
|
|
/// This is the default behavior. The rollback journal is deleted at the conclusion of each
|
|
/// transaction. The delete operation itself causes the transaction to commit.
|
|
///
|
|
/// - SeeAlso: [Atomic Commit In SQLite](https://sqlite.org/atomiccommit.html)
|
|
case delete
|
|
|
|
/// TRUNCATE journal mode.
|
|
///
|
|
/// In this mode, the rollback journal is truncated to zero length at the end of each
|
|
/// transaction instead of being deleted. On many systems, truncating a file is much faster than
|
|
/// deleting it because truncating does not require modifying the containing directory.
|
|
case truncate
|
|
|
|
/// PERSIST journal mode.
|
|
///
|
|
/// In this mode, the rollback journal is not deleted at the end of each transaction. Instead,
|
|
/// the header of the journal is overwritten with zeros. This prevents other database
|
|
/// connections from rolling the journal back. The PERSIST mode is useful as an optimization on
|
|
/// platforms where deleting or truncating a file is more expensive than overwriting the first
|
|
/// block of a file with zeros.
|
|
///
|
|
/// - SeeAlso: [journal_size_limit](
|
|
/// https://sqlite.org/pragma.html#pragma_journal_size_limit)
|
|
case persist
|
|
|
|
/// MEMORY journal mode.
|
|
///
|
|
/// In this mode, the rollback journal is stored entirely in volatile RAM rather than on disk.
|
|
/// This saves disk I/O but at the expense of database safety and integrity. If the application
|
|
/// crashes during a transaction, the database file will likely become corrupt.
|
|
case memory
|
|
|
|
/// Write-Ahead Logging (WAL) journal mode.
|
|
///
|
|
/// This mode uses a write-ahead log instead of a rollback journal to implement transactions.
|
|
/// The WAL mode is persistent, meaning it stays in effect across multiple database connections
|
|
/// and persists even after closing and reopening the database.
|
|
///
|
|
/// - SeeAlso: [Write-Ahead Logging](https://sqlite.org/wal.html)
|
|
case wal
|
|
|
|
/// OFF journal mode.
|
|
///
|
|
/// In this mode, the rollback journal is completely disabled, meaning no rollback journal is
|
|
/// ever created. This disables SQLite's atomic commit and rollback capabilities. The `ROLLBACK`
|
|
/// command will no longer work and behaves in an undefined way. Applications must avoid using
|
|
/// the `ROLLBACK` command when the journal mode is OFF. If the application crashes in the
|
|
/// middle of a transaction, the database file will likely become corrupt, as there is no way to
|
|
/// unwind partially completed operations. For example, if a duplicate entry causes a
|
|
/// `CREATE UNIQUE INDEX` statement to fail halfway through, it will leave behind a partially
|
|
/// created index, resulting in a corrupted database state.
|
|
case off
|
|
|
|
/// The string representation of the journal mode recognized by SQLite.
|
|
///
|
|
/// Each case maps to its corresponding uppercase string value expected by SQLite. For example,
|
|
/// `.wal` maps to `"WAL"`. This value is typically used when reading or setting the journal mode
|
|
/// through the `PRAGMA journal_mode` command.
|
|
///
|
|
/// - Returns: The uppercase string identifier of the journal mode as understood by SQLite.
|
|
///
|
|
/// - SeeAlso: [journal_mode](https://sqlite.org/pragma.html#pragma_journal_mode)
|
|
public var rawValue: String {
|
|
switch self {
|
|
case .delete: "DELETE"
|
|
case .truncate: "TRUNCATE"
|
|
case .persist: "PERSIST"
|
|
case .memory: "MEMORY"
|
|
case .wal: "WAL"
|
|
case .off: "OFF"
|
|
}
|
|
}
|
|
|
|
/// Creates a `JournalMode` instance from a string representation.
|
|
///
|
|
/// The initializer performs a case-insensitive match between the provided string and the known
|
|
/// SQLite journal mode names. If the input does not correspond to any valid journal mode, the
|
|
/// initializer returns `nil`.
|
|
///
|
|
/// - Parameter rawValue: The string name of the journal mode, as defined by SQLite.
|
|
/// - Returns: A `JournalMode` value if the input string matches a supported mode; otherwise,
|
|
/// `nil`.
|
|
///
|
|
/// - SeeAlso: [journal_mode](https://sqlite.org/pragma.html#pragma_journal_mode)
|
|
public init?(rawValue: String) {
|
|
switch rawValue.uppercased() {
|
|
case "DELETE": self = .delete
|
|
case "TRUNCATE": self = .truncate
|
|
case "PERSIST": self = .persist
|
|
case "MEMORY": self = .memory
|
|
case "WAL": self = .wal
|
|
case "OFF": self = .off
|
|
default: return nil
|
|
}
|
|
}
|
|
}
|