Add delete column support (#217)

* Add delete column support

Added deleteColumns to MySQLAlterTable

This change allows columns to be deleted (DROP).  I will build on this
with a pull request to fluent-mysql to allow
MySQLDatabase:SchemaSupporting to bind FluentMySQLSchema.deleteColumns
and thus allowing full column ADD/DROP support.

* Fixed test class name

Aligned MySQLMigrationTests name with the file name

Sadly only caught this in Linux build…

* DROP column refinements

Updates as per code review.

* Changed DROP specification to include only the column name

Since MySql 8.0 will not accept the table name in the column name specification of DROP [COLUMN] (where as 5.7 would) I changed the code to only include the identifier and not the table name.

Author: foscomputerservices

Sources/MySQL/SQL/MySQLAlterTable.swift

@@ -3,6 +3,9 @@ public struct MySQLAlterTable: SQLAlterTable {
     /// See `SQLAlterTable`.
     public typealias ColumnDefinition = MySQLColumnDefinition
 
+    /// See `SQLAlterTable`.
+    public typealias ColumnIdentifier = MySQLColumnIdentifier
+    
     /// See `SQLAlterTable`.
     public typealias TableIdentifier = MySQLTableIdentifier
 
@@ -20,6 +23,9 @@ public struct MySQLAlterTable: SQLAlterTable {
     /// See `SQLAlterTable`.
     public var columns: [ColumnDefinition]
 
+    /// See `FluentSQLSchema`.
+    public var deleteColumns: [ColumnIdentifier]
+    
     /// See `SQLAlterTable`.
     public var constraints: [TableConstraint]
 
@@ -50,6 +56,7 @@ public struct MySQLAlterTable: SQLAlterTable {
     public init(table: TableIdentifier) {
         self.table = table
         self.columns = []
+        self.deleteColumns = []
         self.constraints = []
         self.columnPositions = [:]
     }
@@ -67,7 +74,10 @@ public struct MySQLAlterTable: SQLAlterTable {
                 return sql
             }
         } + constraints.map { "ADD " + $0.serialize(&binds) }
-        sql.append(actions.joined(separator: ", "))
+        let deleteActions = deleteColumns.map {
+            return "DROP " + $0.identifier.serialize(&binds)
+        }
+        sql.append((actions + deleteActions).joined(separator: ", "))
         return sql.joined(separator: " ")
     }
 }

Tests/MySQLTests/MySQLTests.swift

@@ -362,6 +362,69 @@ class MySQLTests: XCTestCase {
         }
     }
 
+    func testDropOneColumn() throws {
+        let client = try MySQLConnection.makeTest()
+        defer { client.close(done: nil) }
+        let dropResults = try client.simpleQuery("DROP TABLE IF EXISTS foos;").wait()
+        XCTAssertEqual(dropResults.count, 0)
+        let createResults = try client.simpleQuery("CREATE TABLE foos (id INT SIGNED, name VARCHAR(64));").wait()
+        XCTAssertEqual(createResults.count, 0)
+        let insertResults = try client.raw("INSERT INTO foos VALUES (?, ?);").bind(-1).bind("vapor").all().wait()
+        XCTAssertEqual(insertResults.count, 0)
+        
+        let preSelectResults = try client.raw("SELECT * FROM foos;").all().wait()
+        XCTAssertEqual(preSelectResults.count, 1)
+        XCTAssertEqual(preSelectResults[0].count, 2) // 2 columns
+        
+        let tableId = MySQLTableIdentifier(stringLiteral: "foos");
+        var migration = MySQLAlterTable(table: tableId)
+        migration.deleteColumns = [
+            MySQLColumnIdentifier.column(MySQLTableIdentifier(stringLiteral: "foos"), MySQLIdentifier.init("name"))
+        ]
+        
+        var binds: [Encodable] = []
+        let sql = migration.serialize(&binds)
+        let migrationResults = try client.raw(sql).all().wait()
+        XCTAssertEqual(migrationResults.count, 0)
+        
+        let postSelectResults = try client.raw("SELECT * FROM foos;").all().wait()
+        XCTAssertEqual(postSelectResults.count, 1)
+        XCTAssertEqual(postSelectResults[0].count, 1) // 1 column
+        XCTAssertEqual(postSelectResults[0].keys.first!, MySQLColumn(table: "foos", name: "id"))
+    }
+    
+    func testDropColumnMultipleColumns() throws {
+        let client = try MySQLConnection.makeTest()
+        defer { client.close(done: nil) }
+        let dropResults = try client.simpleQuery("DROP TABLE IF EXISTS foos;").wait()
+        XCTAssertEqual(dropResults.count, 0)
+        let createResults = try client.simpleQuery("CREATE TABLE foos (id INT SIGNED, name1 VARCHAR(64), name2 VARCHAR(64));").wait()
+        XCTAssertEqual(createResults.count, 0)
+        let insertResults = try client.raw("INSERT INTO foos VALUES (?, ?, ?);").bind(-1).bind("vapor1").bind("vapor2").all().wait()
+        XCTAssertEqual(insertResults.count, 0)
+        
+        let preSelectResults = try client.raw("SELECT * FROM foos;").all().wait()
+        XCTAssertEqual(preSelectResults.count, 1)
+        XCTAssertEqual(preSelectResults[0].count, 3) // 3 columns
+        
+        let tableId = MySQLTableIdentifier(stringLiteral: "foos");
+        var migration = MySQLAlterTable(table: tableId)
+        migration.deleteColumns = [
+            MySQLColumnIdentifier.column(MySQLTableIdentifier(stringLiteral: "foos"), MySQLIdentifier.init("name1")),
+            MySQLColumnIdentifier.column(MySQLTableIdentifier(stringLiteral: "foos"), MySQLIdentifier.init("name2"))
+        ]
+        
+        var binds: [Encodable] = []
+        let sql = migration.serialize(&binds)
+        let migrationResults = try client.raw(sql).all().wait()
+        XCTAssertEqual(migrationResults.count, 0)
+        
+        let postSelectResults = try client.raw("SELECT * FROM foos;").all().wait()
+        XCTAssertEqual(postSelectResults.count, 1)
+        XCTAssertEqual(postSelectResults[0].count, 1) // 1 column
+        XCTAssertEqual(postSelectResults[0].keys.first!, MySQLColumn(table: "foos", name: "id"))
+    }
+    
     static let allTests = [
         ("testBenchmark", testBenchmark),
         ("testSimpleQuery", testSimpleQuery),
@@ -383,6 +446,8 @@ class MySQLTests: XCTestCase {
         ("testZeroLengthArray", testZeroLengthArray),
         ("testMySQLTimeDescription", testMySQLTimeDescription),
         ("testGH223", testGH223),
+        ("testDropOneColumn", testDropOneColumn),
+        ("testDropColumnMultipleColumns", testDropColumnMultipleColumns),
     ]
 }