Apply every RENAME COLUMN in a multi-column MySQL ALTER

convertAlterTableStmt returned on the first RENAME COLUMN spec, so any
further renames in the same ALTER TABLE were dropped and queries using
the later columns failed to compile. Emit an AT_RenameColumn command per
spec, like the other multi-spec actions, and apply it in the catalog.

Fixes #4493

Author: dimasfeb19

internal/endtoend/testdata/ddl_alter_table_rename_column_multiple/mysql/go/db.go

@@ -0,0 +1,2 @@
+/* name: GetFoo :many */
+SELECT qux, quux FROM foo;

internal/endtoend/testdata/ddl_alter_table_rename_column_multiple/mysql/go/models.go

@@ -0,0 +1,4 @@
+CREATE TABLE foo (bar text, baz text);
+ALTER TABLE foo
+    RENAME COLUMN bar TO qux,
+    RENAME COLUMN baz TO quux;

internal/endtoend/testdata/ddl_alter_table_rename_column_multiple/mysql/go/query.sql.go

@@ -0,0 +1,12 @@
+{
+  "version": "1",
+  "packages": [
+    {
+      "path": "go",
+      "engine": "mysql",
+      "name": "querytest",
+      "schema": "schema.sql",
+      "queries": "query.sql"
+    }
+  ]
+}

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

@@ -95,14 +95,13 @@ func (c *cc) convertAlterTableStmt(n *pcast.AlterTableStmt) ast.Node {
 			// 	spew.Dump("add const", spec)
 
 		case pcast.AlterTableRenameColumn:
-			// TODO: Returning here may be incorrect if there are multiple specs
 			oldName := spec.OldColumnName.String()
 			newName := spec.NewColumnName.String()
-			return &ast.RenameColumnStmt{
-				Table:   parseTableName(n.Table),
-				Col:     &ast.ColumnRef{Name: oldName},
-				NewName: &newName,
-			}
+			alt.Cmds.Items = append(alt.Cmds.Items, &ast.AlterTableCmd{
+				Name:    &oldName,
+				Newname: &newName,
+				Subtype: ast.AT_RenameColumn,
+			})
 
 		case pcast.AlterTableRenameTable:
 			// TODO: Returning here may be incorrect if there are multiple specs

internal/endtoend/testdata/ddl_alter_table_rename_column_multiple/mysql/schema.sql

@@ -8,6 +8,7 @@ const (
 	AT_DropColumn
 	AT_DropNotNull
 	AT_SetNotNull
+	AT_RenameColumn
 )
 
 type AlterTableType int
@@ -24,6 +25,8 @@ func (t AlterTableType) String() string {
 		return "DropNotNull"
 	case AT_SetNotNull:
 		return "SetNotNull"
+	case AT_RenameColumn:
+		return "RenameColumn"
 	default:
 		return "Unknown"
 	}
@@ -32,6 +35,7 @@ func (t AlterTableType) String() string {
 type AlterTableCmd struct {
 	Subtype   AlterTableType
 	Name      *string
+	Newname   *string
 	Def       *ColumnDef
 	Newowner  *RoleSpec
 	Behavior  DropBehavior

internal/endtoend/testdata/ddl_alter_table_rename_column_multiple/mysql/sqlc.json

@@ -177,6 +177,8 @@ func isStmtImplemented(stmt *ast.AlterTableStmt) bool {
 				implemented = true
 			case ast.AT_SetNotNull:
 				implemented = true
+			case ast.AT_RenameColumn:
+				implemented = true
 			}
 		}
 	}
@@ -215,6 +217,10 @@ func (c *Catalog) alterTable(stmt *ast.AlterTableStmt) error {
 				if err := table.setNotNull(cmd); err != nil {
 					return err
 				}
+			case ast.AT_RenameColumn:
+				if err := c.renameColumnOnTable(table, *cmd.Name, *cmd.Newname); err != nil {
+					return err
+				}
 			}
 		}
 	}
@@ -394,22 +400,26 @@ func (c *Catalog) renameColumn(stmt *ast.RenameColumnStmt) error {
 	if err != nil {
 		return checkMissing(err, stmt.MissingOk)
 	}
+	return c.renameColumnOnTable(tbl, stmt.Col.Name, *stmt.NewName)
+}
+
+func (c *Catalog) renameColumnOnTable(tbl *Table, oldName, newName string) error {
 	idx := -1
 	for i := range tbl.Columns {
-		if tbl.Columns[i].Name == stmt.Col.Name {
+		if tbl.Columns[i].Name == oldName {
 			idx = i
 		}
-		if tbl.Columns[i].Name == *stmt.NewName {
-			return sqlerr.ColumnExists(tbl.Rel.Name, *stmt.NewName)
+		if tbl.Columns[i].Name == newName {
+			return sqlerr.ColumnExists(tbl.Rel.Name, newName)
 		}
 	}
 	if idx == -1 {
-		return sqlerr.ColumnNotFound(tbl.Rel.Name, stmt.Col.Name)
+		return sqlerr.ColumnNotFound(tbl.Rel.Name, oldName)
 	}
-	tbl.Columns[idx].Name = *stmt.NewName
+	tbl.Columns[idx].Name = newName
 
 	if tbl.Columns[idx].linkedType {
-		name := fmt.Sprintf("%s_%s", tbl.Rel.Name, *stmt.NewName)
+		name := fmt.Sprintf("%s_%s", tbl.Rel.Name, newName)
 		rename := &ast.RenameTypeStmt{
 			Type:    &tbl.Columns[idx].Type,
 			NewName: &name,