add iOS

2025-01-28 12:28:03 +08:00
parent 738c373a77
commit ec96756800
2534 changed files with 486292 additions and 0 deletions
@@ -0,0 +1,86 @@
+/// An internal struct that defines a migration.
+struct Migration {
+    enum ForeignKeyChecks {
+        case deferred
+        case immediate
+        case disabled
+    }
+    
+    let identifier: String
+    var foreignKeyChecks: ForeignKeyChecks
+    let migrate: (Database) throws -> Void
+    
+    func run(_ db: Database) throws {
+        if try Bool.fetchOne(db, sql: "PRAGMA foreign_keys") ?? false {
+            switch foreignKeyChecks {
+            case .deferred:
+                try runWithDeferredForeignKeysChecks(db)
+            case .immediate:
+                try runWithImmediateForeignKeysChecks(db)
+            case .disabled:
+                try runWithDisabledForeignKeysChecks(db)
+            }
+        } else {
+            try runWithImmediateForeignKeysChecks(db)
+        }
+    }
+    
+    private func runWithImmediateForeignKeysChecks(_ db: Database) throws {
+        try db.inTransaction(.immediate) {
+            try migrate(db)
+            try insertAppliedIdentifier(db)
+            return .commit
+        }
+    }
+    
+    private func runWithDisabledForeignKeysChecks(_ db: Database) throws {
+        try db.execute(sql: "PRAGMA foreign_keys = OFF")
+        try throwingFirstError(
+            execute: {
+                try db.inTransaction(.immediate) {
+                    try migrate(db)
+                    try insertAppliedIdentifier(db)
+                    return .commit
+                }
+            },
+            finally: {
+                try db.execute(sql: "PRAGMA foreign_keys = ON")
+            })
+    }
+
+    private func runWithDeferredForeignKeysChecks(_ db: Database) throws {
+        // Support for database alterations described at
+        // https://www.sqlite.org/lang_altertable.html#otheralter
+        //
+        // > 1. If foreign key constraints are enabled, disable them using
+        // > PRAGMA foreign_keys=OFF.
+        try db.execute(sql: "PRAGMA foreign_keys = OFF")
+        
+        try throwingFirstError(
+            execute: {
+                // > 2. Start a transaction.
+                try db.inTransaction(.immediate) {
+                    try migrate(db)
+                    try insertAppliedIdentifier(db)
+                    
+                    // > 10. If foreign key constraints were originally enabled
+                    // > then run PRAGMA foreign_key_check to verify that the
+                    // > schema change did not break any foreign
+                    // > key constraints.
+                    try db.checkForeignKeys()
+                    
+                    // > 11. Commit the transaction started in step 2.
+                    return .commit
+                }
+            },
+            finally: {
+                // > 12. If foreign keys constraints were originally enabled,
+                // > reenable them now.
+                try db.execute(sql: "PRAGMA foreign_keys = ON")
+            })
+    }
+    
+    private func insertAppliedIdentifier(_ db: Database) throws {
+        try db.execute(sql: "INSERT INTO grdb_migrations (identifier) VALUES (?)", arguments: [identifier])
+    }
+}