Merge pull request stephencelis#853 from hellohuanlin/huan_primary_key_with_4_columns

add primary key with 4 columns

Author: ypopovych

Sources/SQLite/Typed/Schema.swift

@@ -341,6 +341,10 @@ public final class TableBuilder {
         primaryKey([compositeA, b, c])
     }
 
+    public func primaryKey<T : Value, U : Value, V : Value, W : Value>(_ compositeA: Expression<T>, _ b: Expression<U>, _ c: Expression<V>, _ d: Expression<W>) {
+        primaryKey([compositeA, b, c, d])
+    }
+
     fileprivate func primaryKey(_ composite: [Expressible]) {
         definitions.append("PRIMARY KEY".prefix(composite))
     }

Tests/SQLiteTests/SchemaTests.swift

@@ -545,6 +545,10 @@ class SchemaTests : XCTestCase {
             "CREATE TABLE \"table\" (PRIMARY KEY (\"int64\", \"string\", \"double\"))",
             table.create { t in t.primaryKey(int64, string, double) }
         )
+        XCTAssertEqual(
+            "CREATE TABLE \"table\" (PRIMARY KEY (\"int64\", \"string\", \"double\", \"date\"))",
+            table.create { t in t.primaryKey(int64, string, double, date) }
+        )
     }
 
     func test_unique_compilesUniqueExpression() {