Add broader support for MySQL DDL statements (#675)

* endtoend: Update drop column test

* dolphin: Add test for ALTER TABLE DROP COLUMN

* dolphin: Implement ALTER TABLE MODIFY COLUMN

* dolphin: Implement DROP COLUMN IF NOT EXISTS

* dolphin: Implement ALTER TABLE DROP CONSTRAINT

* endtoend: Combine similar DROP NOT NULL tests

* dolphin: Implement ALTER TABLE RENAME TO

* dolphin: Remove duplicate RENAME TABLE test

* dolphin: Implement ALTER TABLE RENAME COLUMN

* dolphin: Add test for changing column data type

* dolphin: Add test for setting column as not null

* dolphin: Fix failing tests

* dolphin: Skip ALTER TABLE SET SCHEMA

* dolphin: Support table and column comments

Author: kyleconroy

internal/codegen/golang/mysql_type.go

@@ -65,6 +65,9 @@ func mysqlType(r *compiler.Result, col *compiler.Column, settings config.Combine
 	case "json":
 		return "json.RawMessage"
 
+	case "any":
+		return "interface{}"
+
 	default:
 		log.Printf("unknown MySQL type: %s\n", columnType)
 		return "interface{}"

internal/endtoend/testdata/ddl_alter_table_drop_not_null/postgresql/go/db.go renamed to internal/endtoend/testdata/ddl_alter_table_column_drop_not_null/mysql/go/db.go

@@ -0,0 +1,2 @@
+/* name: Placeholder :exec */
+SELECT 1;

internal/endtoend/testdata/ddl_alter_table_drop_not_null/postgresql/go/models.go renamed to internal/endtoend/testdata/ddl_alter_table_column_drop_not_null/mysql/go/models.go

@@ -0,0 +1,3 @@
+CREATE TABLE foo (bar text NOT NULL, baz text NOT NULL);
+ALTER TABLE foo MODIFY COLUMN bar text;
+ALTER TABLE foo MODIFY baz text;

internal/endtoend/testdata/ddl_alter_table_drop_not_null/postgresql/go/query.sql.go renamed to internal/endtoend/testdata/ddl_alter_table_column_drop_not_null/mysql/go/query.sql.go

@@ -3,10 +3,10 @@
   "packages": [
     {
       "path": "go",
-      "engine": "postgresql",
+      "engine": "mysql:beta",
       "name": "querytest",
       "schema": "schema.sql",
       "queries": "query.sql"
     }
   ]
-}
+}

internal/endtoend/testdata/ddl_alter_table_column_drop_not_null/mysql/query.sql

@@ -1,2 +1,3 @@
-CREATE TABLE foo (bar text NOT NULL);
-ALTER TABLE foo ALTER COLUMN bar DROP NOT NULL;
+CREATE TABLE foo (bar text NOT NULL, baz text NOT NULL);
+ALTER TABLE foo ALTER COLUMN bar DROP NOT NULL;
+ALTER TABLE foo ALTER baz DROP NOT NULL;