Merge pull request #337 from groue/GRDB3-autoIncrementedPrimaryKey

Foster auto-incremented primary keys

GRDB/Core/Database.swift

@@ -888,7 +888,7 @@ extension Database {
     /// An SQL column type.
     ///
     ///     try db.create(table: "players") { t in
-    ///         t.column("id", .integer).primaryKey()
+    ///         t.autoIncrementedPrimaryKey("id")
     ///         t.column("title", .text)
     ///     }
     ///

GRDB/QueryInterface/TableDefinition.swift

@@ -6,7 +6,7 @@ extension Database {
     /// Creates a database table.
     ///
     ///     try db.create(table: "pointOfInterests") { t in
-    ///         t.column("id", .integer).primaryKey()
+    ///         t.autoIncrementedPrimaryKey("id")
     ///         t.column("title", .text)
     ///         t.column("favorite", .boolean).notNull().default(false)
     ///         t.column("longitude", .double).notNull()
@@ -35,7 +35,7 @@ extension Database {
     /// Creates a database table.
     ///
     ///     try db.create(table: "pointOfInterests") { t in
-    ///         t.column("id", .integer).primaryKey()
+    ///         t.autoIncrementedPrimaryKey("id")
     ///         t.column("title", .text)
     ///         t.column("favorite", .boolean).notNull().default(false)
     ///         t.column("longitude", .double).notNull()
@@ -67,7 +67,7 @@ extension Database {
     /// Creates a database table.
     ///
     ///     try db.create(table: "pointOfInterests") { t in
-    ///         t.column("id", .integer).primaryKey()
+    ///         t.autoIncrementedPrimaryKey("id")
     ///         t.column("title", .text)
     ///         t.column("favorite", .boolean).notNull().default(false)
     ///         t.column("longitude", .double).notNull()
@@ -248,6 +248,38 @@ public final class TableDefinition {
         self.withoutRowID = withoutRowID
     }
 
+    /// Defines the auto-incremented primary key.
+    ///
+    ///     try db.create(table: "players") { t in
+    ///         t.autoIncrementedPrimaryKey("id")
+    ///     }
+    ///
+    /// The auto-incremented primary key is an integer primary key that
+    /// automatically generates unused values when you do not explicitely
+    /// provide one, and prevents the reuse of ids over the lifetime of
+    /// the database.
+    ///
+    /// **It is the preferred way to define a numeric primary key**.
+    ///
+    /// The fact that an auto-incremented primary key prevents the reuse of
+    /// ids is an excellent guard against data races that could happen when your
+    /// application processes ids in an asynchronous way. The auto-incremented
+    /// primary key provides the guarantee that a given id can't reference a row
+    /// that is different from the one it used to be at the beginning of the
+    /// asynchronous process, even if this row gets deleted and a new one is
+    /// inserted in between.
+    ///
+    /// See https://www.sqlite.org/lang_createtable.html#primkeyconst and
+    /// https://www.sqlite.org/lang_createtable.html#rowid
+    ///
+    /// - parameter conflitResolution: An optional conflict resolution
+    ///   (see https://www.sqlite.org/lang_conflict.html).
+    /// - returns: Self so that you can further refine the column definition.
+    @discardableResult
+    public func autoIncrementedPrimaryKey(_ name: String, onConflict conflictResolution: Database.ConflictResolution? = nil) -> ColumnDefinition {
+        return column(name, .integer).primaryKey(onConflict: conflictResolution, autoincrement: true)
+    }
+
     /// Appends a table column.
     ///
     ///     try db.create(table: "players") { t in

GRDB/Record/TableRecord.swift

@@ -104,7 +104,7 @@ extension TableRecord {
     ///
     ///     try dbQueue.write { db in
     ///         try db.create(table: "players") { t in
-    ///             t.column("id", .integer).primaryKey()
+    ///             t.autoIncrementedPrimaryKey("id")
     ///             t.column("name", .text)
     ///             t.column("score", .integer)
     ///         }

README.md

@@ -166,7 +166,7 @@ Avoid SQL with the [query interface](#the-query-interface):
 ```swift
 try dbQueue.write { db in
     try db.create(table: "places") { t in
-        t.column("id", .integer).primaryKey()
+        t.autoIncrementedPrimaryKey("id")
         t.column("title", .text).notNull()
         t.column("favorite", .boolean).notNull().defaults(to: false)
         t.column("longitude", .double).notNull()
@@ -1707,7 +1707,7 @@ Int.fetchOne(db, Player.select(maxLength.apply(nameColumn))) // Int?
 
 ```swift
 try db.create(table: "players") { t in
-    t.column("id", .integer).primaryKey()
+    t.autoIncrementedPrimaryKey("id")
     t.column("name", .text)
 }
 
@@ -2660,7 +2660,7 @@ The [five different policies](https://www.sqlite.org/lang_conflict.html) are: ab
     //     email TEXT UNIQUE ON CONFLICT REPLACE
     // )
     try db.create(table: "players") { t in
-        t.column("id", .integer).primaryKey()
+        t.autoIncrementedPrimaryKey("id")
         t.column("email", .text).unique(onConflict: .replace) // <--
     }
 
@@ -2678,7 +2678,7 @@ The [five different policies](https://www.sqlite.org/lang_conflict.html) are: ab
     //     email TEXT UNIQUE
     // )
     try db.create(table: "players") { t in
-        t.column("id", .integer).primaryKey()
+        t.autoIncrementedPrimaryKey("id")
         t.column("email", .text)
     }
 
@@ -3013,7 +3013,7 @@ Once granted with a [database connection](#database-connections), you can setup
 //   longitude DOUBLE NOT NULL
 // )
 try db.create(table: "places") { t in
-    t.column("id", .integer).primaryKey()
+    t.autoIncrementedPrimaryKey("id")
     t.column("title", .text)
     t.column("favorite", .boolean).notNull().defaults(to: false)
     t.column("longitude", .double).notNull()
@@ -3067,8 +3067,11 @@ Define **not null** columns, and set **default** values:
 Use an individual column as **primary**, **unique**, or **foreign key**. When defining a foreign key, the referenced column is the primary key of the referenced table (unless you specify otherwise):
 
 ```swift
-    // id INTEGER PRIMARY KEY,
-    t.column("id", .integer).primaryKey()
+    // id INTEGER PRIMARY KEY AUTOINCREMENT,
+    t.autoIncrementedPrimaryKey("id")
+
+    // uuid TEXT PRIMARY KEY,
+    t.column("uuid", .text).primaryKey()
 
     // email TEXT UNIQUE,
     t.column("email", .text).unique()
@@ -3077,6 +3080,10 @@ Use an individual column as **primary**, **unique**, or **foreign key**. When de
     t.column("countryCode", .text).references("countries", onDelete: .cascade)
 ```
 
+> :bulb: **Tip**: when you need an integer primary key that automatically generates unique values, it is highly recommended that you use the `autoIncrementedPrimaryKey` method.
+>
+> Such primary key prevents the reuse of ids, and is an excellent guard against data races that could happen when your application processes ids in an asynchronous way. The auto-incremented primary key provides the guarantee that a given id can't reference a row that is different from the one it used to be at the beginning of the asynchronous process, even if this row gets deleted and a new one is inserted in between.
+
 **Create an index** on the column:
 
 ```swift

Tests/GRDBTests/TableDefinitionTests.swift

@@ -65,6 +65,32 @@ class TableDefinitionTests: GRDBTestCase {
         }
     }
 
+    func testAutoIncrementedPrimaryKey() throws {
+        let dbQueue = try makeDatabaseQueue()
+        try dbQueue.inTransaction { db in
+            try db.create(table: "test") { t in
+                t.autoIncrementedPrimaryKey("id")
+            }
+            assertEqualSQL(lastSQLQuery, """
+                CREATE TABLE "test" (\
+                "id" INTEGER PRIMARY KEY AUTOINCREMENT\
+                )
+                """)
+            return .rollback
+        }
+        try dbQueue.inTransaction { db in
+            try db.create(table: "test") { t in
+                t.autoIncrementedPrimaryKey("id", onConflict: .fail)
+            }
+            assertEqualSQL(lastSQLQuery, """
+                CREATE TABLE "test" (\
+                "id" INTEGER PRIMARY KEY ON CONFLICT FAIL AUTOINCREMENT\
+                )
+                """)
+            return .rollback
+        }
+    }
+
     func testColumnPrimaryKeyOptions() throws {
         let dbQueue = try makeDatabaseQueue()
         try dbQueue.inTransaction { db in