GRDB/Configuration

The configuration of a database connection.

Overview

You create a Configuration before opening a database connection:

var config = Configuration()
config.readonly = true
config.maximumReaderCount = 2  // (DatabasePool only) The default is 5

let dbQueue = try DatabaseQueue( // or DatabasePool
    path: "/path/to/database.sqlite",
    configuration: config)

See doc:DatabaseConnections.

Frequent Use Cases

Tracing SQL Statements

You can setup a tracing function that prints out all executed SQL requests with prepareDatabase(_:) and Database/trace(options:_:):

var config = Configuration()
config.prepareDatabase { db in
    db.trace { print("SQL> \($0)") }
}

let dbQueue = try DatabaseQueue(
    path: "/path/to/database.sqlite",
    configuration: config)

// Prints "SQL> SELECT COUNT(*) FROM player"
let playerCount = dbQueue.read { db in
    try Player.fetchCount(db)
}

Public Statement Arguments

Debugging is easier when database errors and tracing functions expose the values sent to the database. Since those values may contain sensitive information, verbose logging is disabled by default. You turn it on with publicStatementArguments:

var config = Configuration()
#if DEBUG
// Protect sensitive information by enabling
// verbose debugging in DEBUG builds only.
config.publicStatementArguments = true
#endif

let dbQueue = try DatabaseQueue(
    path: "/path/to/database.sqlite",
    configuration: config)

do {
    try dbQueue.write { db in
        user.name = ...
        user.location = ...
        user.address = ...
        user.phoneNumber = ...
        try user.save(db)
    }
} catch {
    // Prints sensitive information in debug builds only
    print(error)
}

Warning: It is your responsibility to prevent sensitive information from leaking in unexpected locations, so you should not set the publicStatementArguments flag in release builds (think about GDPR and other privacy-related rules).

Topics

Creating a Configuration

• init()

Configuring SQLite Connections

• acceptsDoubleQuotedStringLiterals
• busyMode
• foreignKeysEnabled
• journalMode
• readonly
• JournalModeConfiguration

Configuring GRDB Connections

• allowsUnsafeTransactions
• label
• maximumReaderCount
• observesSuspensionNotifications
• persistentReadOnlyConnections
• prepareDatabase(_:)
• publicStatementArguments
• schemaSource
• transactionClock
• TransactionClock

Configuring the Quality of Service

• qos
• readQoS
• writeQoS
• targetQueue
• writeTargetQueue

Supporting Types

• DatabaseSchemaSource