ALTER TABLE support for ADD COLUMN, DROP COLUMN, and RENAME COLUMN

server/ast/alter_table.go

@@ -70,17 +70,25 @@ func nodeAlterTableCmds(
 
 	vitessDdlCmds := make([]*vitess.DDL, 0, len(node))
 	for _, cmd := range node {
+		var err error
+		var statement *vitess.DDL
 		switch cmd := cmd.(type) {
 		case *tree.AlterTableAddConstraint:
-			statement, err := nodeAlterTableAddConstraint(cmd, tableName, ifExists)
-			if err != nil {
-				return nil, err
-			}
-			vitessDdlCmds = append(vitessDdlCmds, statement)
-
+			statement, err = nodeAlterTableAddConstraint(cmd, tableName, ifExists)
+		case *tree.AlterTableAddColumn:
+			statement, err = nodeAlterTableAddColumn(cmd, tableName, ifExists)
+		case *tree.AlterTableDropColumn:
+			statement, err = nodeAlterTableDropColumn(cmd, tableName, ifExists)
+		case *tree.AlterTableRenameColumn:
+			statement, err = nodeAlterTableRenameColumn(cmd, tableName, ifExists)
 		default:
 			return nil, fmt.Errorf("ALTER TABLE with unsupported command type %T", cmd)
 		}
+
+		if err != nil {
+			return nil, err
+		}
+		vitessDdlCmds = append(vitessDdlCmds, statement)
 	}
 
 	return vitessDdlCmds, nil
@@ -124,3 +132,68 @@ func nodeAlterTableAddConstraint(
 			"definition type %T", node)
 	}
 }
+
+// nodeAlterTableAddColumn converts a tree.AlterTableAddColumn instance into an equivalent vitess.DDL instance.
+func nodeAlterTableAddColumn(node *tree.AlterTableAddColumn, tableName vitess.TableName, ifExists bool) (*vitess.DDL, error) {
+	if node.IfNotExists {
+		return nil, fmt.Errorf("IF NOT EXISTS on a column in an ADD COLUMN statement is not supported yet")
+	}
+
+	vitessColumnDef, err := nodeColumnTableDef(node.ColumnDef)
+	if err != nil {
+		return nil, err
+	}
+
+	return &vitess.DDL{
+		Action:       "alter",
+		ColumnAction: "add",
+		Table:        tableName,
+		IfExists:     ifExists,
+		Column:       vitessColumnDef.Name,
+		TableSpec: &vitess.TableSpec{
+			Columns: []*vitess.ColumnDefinition{
+				{
+					Name: vitessColumnDef.Name,
+					Type: vitessColumnDef.Type,
+				},
+			},
+		},
+	}, nil
+}
+
+// nodeAlterTableDropColumn converts a tree.AlterTableDropColumn instance into an equivalent vitess.DDL instance.
+func nodeAlterTableDropColumn(node *tree.AlterTableDropColumn, tableName vitess.TableName, ifExists bool) (*vitess.DDL, error) {
+	if node.IfExists {
+		return nil, fmt.Errorf("IF EXISTS on a column in a DROP COLUMN statement is not supported yet")
+	}
+
+	switch node.DropBehavior {
+	case tree.DropDefault:
+	case tree.DropRestrict:
+		return nil, fmt.Errorf("ALTER TABLE DROP COLUMN does not support RESTRICT option")
+	case tree.DropCascade:
+		return nil, fmt.Errorf("ALTER TABLE DROP COLUMN does not support CASCADE option")
+	default:
+		return nil, fmt.Errorf("ALTER TABLE with unsupported drop behavior %v", node.DropBehavior)
+	}
+
+	return &vitess.DDL{
+		Action:       "alter",
+		ColumnAction: "drop",
+		Table:        tableName,
+		IfExists:     ifExists,
+		Column:       vitess.NewColIdent(node.Column.String()),
+	}, nil
+}
+
+// nodeAlterTableRenameColumn converts a tree.AlterTableRenameColumn instance into an equivalent vitess.DDL instance.
+func nodeAlterTableRenameColumn(node *tree.AlterTableRenameColumn, tableName vitess.TableName, ifExists bool) (*vitess.DDL, error) {
+	return &vitess.DDL{
+		Action:       "alter",
+		ColumnAction: "rename",
+		Table:        tableName,
+		IfExists:     ifExists,
+		Column:       vitess.NewColIdent(node.Column.String()),
+		ToColumn:     vitess.NewColIdent(node.NewName.String()),
+	}, nil
+}

testing/go/alter_table_test.go

@@ -110,3 +110,90 @@ func TestAlterTableAddPrimaryKey(t *testing.T) {
 		},
 	})
 }
+
+func TestAlterTableAddColumn(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "Add Column",
+			SetUpScript: []string{
+				"CREATE TABLE test1 (a INT, b INT);",
+				"INSERT INTO test1 VALUES (1, 1);",
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query:    "ALTER TABLE test1 ADD COLUMN c INT NOT NULL DEFAULT 42;",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "select * from test1;",
+					Expected: []sql.Row{{1, 1, 42}},
+				},
+			},
+		},
+	})
+}
+
+func TestAlterTableDropColumn(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "Drop Column",
+			SetUpScript: []string{
+				"CREATE TABLE test1 (a INT, b INT, c INT, d INT);",
+				"INSERT INTO test1 VALUES (1, 2, 3, 4);",
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query:    "ALTER TABLE test1 DROP COLUMN c;",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "select * from test1;",
+					Expected: []sql.Row{{1, 2, 4}},
+				},
+				{
+					Query:    "ALTER TABLE test1 DROP COLUMN d;",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "select * from test1;",
+					Expected: []sql.Row{{1, 2}},
+				},
+				{
+					// TODO: Skipped until we support conditional execution on existence of column
+					Skip:     true,
+					Query:    "ALTER TABLE test1 DROP COLUMN IF EXISTS zzz;",
+					Expected: []sql.Row{},
+				},
+				{
+					// TODO: Even though we're setting IF EXISTS, this query still fails with an
+					//       error about the table not existing.
+					Skip:     true,
+					Query:    "ALTER TABLE IF EXISTS doesNotExist DROP COLUMN z;",
+					Expected: []sql.Row{},
+				},
+			},
+		},
+	})
+}
+
+func TestAlterTableRenameColumn(t *testing.T) {
+	RunScripts(t, []ScriptTest{
+		{
+			Name: "Rename Column",
+			SetUpScript: []string{
+				"CREATE TABLE test1 (a INT, b INT, c INT, d INT);",
+				"INSERT INTO test1 VALUES (1, 2, 3, 4);",
+			},
+			Assertions: []ScriptTestAssertion{
+				{
+					Query:    "ALTER TABLE test1 RENAME COLUMN c to jjj;",
+					Expected: []sql.Row{},
+				},
+				{
+					Query:    "select * from test1 where jjj=3;",
+					Expected: []sql.Row{{1, 2, 3, 4}},
+				},
+			},
+		},
+	})
+}