add swiftUI code

iOS-SwiftUI-Code/GRDB.swift-6.29.3/GRDB/QueryInterface/Schema/IndexDefinition.swift

@@ -0,0 +1,26 @@
+struct IndexDefinition {
+    let name: String
+    let table: String
+    let expressions: [SQLExpression]
+    let options: IndexOptions
+    let condition: SQLExpression?
+}
+
+/// Index creation options
+public struct IndexOptions: OptionSet, Sendable {
+    public let rawValue: Int
+    
+    public init(rawValue: Int) { self.rawValue = rawValue }
+    
+    /// Only creates the index if it does not already exist.
+    public static let ifNotExists = IndexOptions(rawValue: 1 << 0)
+    
+    /// Creates a unique index.
+    public static let unique = IndexOptions(rawValue: 1 << 1)
+}
+
+extension Database {
+    static func defaultIndexName(on table: String, columns: [String]) -> String {
+        "index_\(table)_on_\(columns.joined(separator: "_"))"
+    }
+}