Add OpRenameColumn for renaming columns (#602)

Add a new `rename_column` operation for performing column renames: ```json { "name": "13_rename_column", "operations": [ { "rename_column": { "table": "employees", "from": "role", "to": "job_title" } } ] } ``` Renaming columns is currently done using the `alter_column` operation: ```json { "name": "13_rename_column", "operations": [ { "alter_column": { "table": "employees", "column": "role", "name": "job_title" } } ] } ``` As of this PR both approaches are valid, but the second approach (using `alter_column` to perform column renames) will be removed as part of #601 Part of #601
xataio · Jan 17, 2025 · 895afe4 · 895afe4
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diff --git a/docs/operations/alter_column/README.md b/docs/operations/alter_column/README.md
@@ -2,4 +2,4 @@
 
 An alter column operation alters the properties of a column. The operation supports several sub-operations, described below.
 
-An alter column operation may contain multiple sub-operations. For example, a single alter column operation may rename a column, change its type, and add a check constraint.
+An alter column operation may contain multiple sub-operations. For example, a single alter column operation may change its type, and add a check constraint.
diff --git a/...operations/alter_column/rename_column.mdx → docs/operations/rename_column.mdx b/...operations/alter_column/rename_column.mdx → docs/operations/rename_column.mdx
@@ -7,7 +7,7 @@ description: A rename column operation renames a column.
 
 ```json
 {
-  "alter_column": {
+  "rename_column": {
     "table": "table name",
     "column": "old column name",
     "name": "new column name"

diff --git a/examples/13_rename_column.json b/examples/13_rename_column.json
@@ -2,10 +2,10 @@
   "name": "13_rename_column",
   "operations": [
     {
-      "alter_column": {
+      "rename_column": {
         "table": "employees",
-        "column": "role",
-        "name": "job_title"
+        "from": "role",
+        "to": "job_title"
       }
     }
   ]

diff --git a/examples/35_alter_column_multiple.json b/examples/35_alter_column_multiple.json
@@ -5,7 +5,6 @@
       "alter_column": {
         "table": "events",
         "column": "name",
-        "name": "event_name",
         "type": "text",
         "default": "'unknown event'",
         "nullable": false,

diff --git a/examples/36_set_comment_to_null.json b/examples/36_set_comment_to_null.json
@@ -4,10 +4,10 @@
     {
       "alter_column": {
         "table": "events",
-        "column": "event_name",
+        "column": "name",
         "comment": null,
-        "up": "event_name",
-        "down": "event_name"
+        "up": "name",
+        "down": "name"
       }
     }
   ]

diff --git a/pkg/migrations/op_common.go b/pkg/migrations/op_common.go
@@ -14,6 +14,7 @@ type OpName string
 const (
 	OpNameCreateTable               OpName = "create_table"
 	OpNameRenameTable               OpName = "rename_table"
+	OpNameRenameColumn              OpName = "rename_column"
 	OpNameDropTable                 OpName = "drop_table"
 	OpNameAddColumn                 OpName = "add_column"
 	OpNameDropColumn                OpName = "drop_column"
@@ -99,6 +100,9 @@ func (v *Operations) UnmarshalJSON(data []byte) error {
 		case OpNameAddColumn:
 			item = &OpAddColumn{}
 
+		case OpNameRenameColumn:
+			item = &OpRenameColumn{}
+
 		case OpNameDropColumn:
 			item = &OpDropColumn{}
 
@@ -191,6 +195,9 @@ func OperationName(op Operation) OpName {
 	case *OpDropColumn:
 		return OpNameDropColumn
 
+	case *OpRenameColumn:
+		return OpNameRenameColumn
+
 	case *OpRenameConstraint:
 		return OpNameRenameConstraint
 

diff --git a/pkg/migrations/op_rename_column.go b/pkg/migrations/op_rename_column.go
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: Apache-2.0
+package migrations
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/lib/pq"
+	"github.com/xataio/pgroll/pkg/db"
+	"github.com/xataio/pgroll/pkg/schema"
+)
+
+var _ Operation = (*OpRenameColumn)(nil)
+
+func (o *OpRenameColumn) Start(ctx context.Context, conn db.DB, latestSchema string, tr SQLTransformer, s *schema.Schema, cbs ...CallbackFn) (*schema.Table, error) {
+	// Rename the table in the in-memory schema.
+	table := s.GetTable(o.Table)
+	table.RenameColumn(o.From, o.To)
+
+	return nil, nil
+}
+
+func (o *OpRenameColumn) Complete(ctx context.Context, conn db.DB, tr SQLTransformer, s *schema.Schema) error {
+	// Rename the column
+	_, err := conn.ExecContext(ctx, fmt.Sprintf("ALTER TABLE IF EXISTS %s RENAME COLUMN %s TO %s",
+		pq.QuoteIdentifier(o.Table),
+		pq.QuoteIdentifier(o.From),
+		pq.QuoteIdentifier(o.To)))
+
+	return err
+}
+
+func (o *OpRenameColumn) Rollback(ctx context.Context, conn db.DB, tr SQLTransformer, s *schema.Schema) error {
+	// Rename the column back to the original name in the in-memory schema.
+	table := s.GetTable(o.Table)
+	table.RenameColumn(o.To, o.From)
+
+	return nil
+}
+
+func (o *OpRenameColumn) Validate(ctx context.Context, s *schema.Schema) error {
+	table := s.GetTable(o.Table)
+
+	// Ensure that the table exists.
+	if table == nil {
+		return TableDoesNotExistError{Name: o.Table}
+	}
+
+	// Ensure that the column exists.
+	if table.GetColumn(o.From) == nil {
+		return ColumnDoesNotExistError{Table: o.Table, Name: o.From}
+	}
+
+	// Ensure that the new column name does not already exist
+	if table.GetColumn(o.To) != nil {
+		return ColumnAlreadyExistsError{Table: o.Table, Name: o.To}
+	}
+
+	// Update the in-memory schema to reflect the column rename so that it is
+	// visible to subsequent operations' validation steps.
+	table.RenameColumn(o.From, o.To)
+
+	return nil
+}
diff --git a/pkg/migrations/op_rename_column_test.go b/pkg/migrations/op_rename_column_test.go
@@ -98,3 +98,159 @@ func TestRenameColumn(t *testing.T) {
 		wantStartErr: migrations.ColumnAlreadyExistsError{Table: "users", Name: "id"},
 	}})
 }
+
+func TestOpRenameColumn(t *testing.T) {
+	t.Parallel()
+
+	ExecuteTests(t, TestCases{
+		{
+			name: "rename column",
+			migrations: []migrations.Migration{
+				{
+					Name: "01_create_table",
+					Operations: migrations.Operations{
+						&migrations.OpCreateTable{
+							Name: "users",
+							Columns: []migrations.Column{
+								{
+									Name: "id",
+									Type: "serial",
+									Pk:   true,
+								},
+								{
+									Name:     "username",
+									Type:     "varchar(255)",
+									Nullable: false,
+								},
+							},
+						},
+					},
+				},
+				{
+					Name: "02_rename_column",
+					Operations: migrations.Operations{
+						&migrations.OpRenameColumn{
+							Table: "users",
+							From:  "username",
+							To:    "name",
+						},
+					},
+				},
+			},
+			afterStart: func(t *testing.T, db *sql.DB, schema string) {
+				// The column in the underlying table has not been renamed.
+				ColumnMustExist(t, db, schema, "users", "username")
+
+				// Insertions to the new column name in the new version schema should work.
+				MustInsert(t, db, schema, "02_rename_column", "users", map[string]string{
+					"name": "alice",
+				})
+
+				// Insertions to the old column name in the old version schema should work.
+				MustInsert(t, db, schema, "01_create_table", "users", map[string]string{
+					"username": "bob",
+				})
+
+				// Data can be read from the view in the new version schema.
+				rows := MustSelect(t, db, schema, "02_rename_column", "users")
+				assert.Equal(t, []map[string]any{
+					{"id": 1, "name": "alice"},
+					{"id": 2, "name": "bob"},
+				}, rows)
+			},
+			afterRollback: func(t *testing.T, db *sql.DB, schema string) {
+				// no-op
+			},
+			afterComplete: func(t *testing.T, db *sql.DB, schema string) {
+				// The column in the underlying table has been renamed.
+				ColumnMustExist(t, db, schema, "users", "name")
+
+				// Data can be read from the view in the new version schema.
+				rows := MustSelect(t, db, schema, "02_rename_column", "users")
+				assert.Equal(t, []map[string]any{
+					{"id": 1, "name": "alice"},
+					{"id": 2, "name": "bob"},
+				}, rows)
+			},
+		},
+	})
+}
+
+func TestOpRenameColumnValidation(t *testing.T) {
+	t.Parallel()
+
+	createTableMigration := migrations.Migration{
+		Name: "01_create_table",
+		Operations: migrations.Operations{
+			&migrations.OpCreateTable{
+				Name: "users",
+				Columns: []migrations.Column{
+					{
+						Name: "id",
+						Type: "serial",
+						Pk:   true,
+					},
+					{
+						Name:     "username",
+						Type:     "varchar(255)",
+						Nullable: false,
+					},
+				},
+			},
+		},
+	}
+
+	ExecuteTests(t, TestCases{
+		{
+			name: "table must exist",
+			migrations: []migrations.Migration{
+				createTableMigration,
+				{
+					Name: "02_rename_column",
+					Operations: migrations.Operations{
+						&migrations.OpRenameColumn{
+							Table: "doesntexist",
+							From:  "username",
+							To:    "id",
+						},
+					},
+				},
+			},
+			wantStartErr: migrations.TableDoesNotExistError{Name: "doesntexist"},
+		},
+		{
+			name: "source column must exist",
+			migrations: []migrations.Migration{
+				createTableMigration,
+				{
+					Name: "02_rename_column",
+					Operations: migrations.Operations{
+						&migrations.OpRenameColumn{
+							Table: "users",
+							From:  "doesntexist",
+							To:    "id",
+						},
+					},
+				},
+			},
+			wantStartErr: migrations.ColumnDoesNotExistError{Table: "users", Name: "doesntexist"},
+		},
+		{
+			name: "target column must not exist",
+			migrations: []migrations.Migration{
+				createTableMigration,
+				{
+					Name: "02_rename_column",
+					Operations: migrations.Operations{
+						&migrations.OpRenameColumn{
+							Table: "users",
+							From:  "username",
+							To:    "id",
+						},
+					},
+				},
+			},
+			wantStartErr: migrations.ColumnAlreadyExistsError{Table: "users", Name: "id"},
+		},
+	})
+}
diff --git a/pkg/migrations/types.go b/pkg/migrations/types.go
diff --git a/schema.json b/schema.json
@@ -262,6 +262,26 @@
       "required": ["column", "table"],
       "type": "object"
     },
+    "OpRenameColumn": {
+      "additionalProperties": false,
+      "description": "Rename column operation",
+      "properties": {
+        "table": {
+          "description": "Name of the table",
+          "type": "string"
+        },
+        "from": {
+          "description": "Old name of the column",
+          "type": "string"
+        },
+        "to": {
+          "description": "New name of the column",
+          "type": "string"
+        }
+      },
+      "required": ["table", "from", "to"],
+      "type": "object"
+    },
     "OpAlterColumn": {
       "additionalProperties": false,
       "description": "Alter column operation",
@@ -710,6 +730,17 @@
           },
           "required": ["alter_column"]
         },
+        {
+          "type": "object",
+          "description": "Rename column operation",
+          "additionalProperties": false,
+          "properties": {
+            "rename_column": {
+              "$ref": "#/$defs/OpRenameColumn"
+            }
+          },
+          "required": ["rename_column"]
+        },
         {
           "type": "object",
           "description": "Create index operation",
Original file line number	Diff line number	Diff line change
Expand Up		@@ -2,4 +2,4 @@

		An alter column operation alters the properties of a column. The operation supports several sub-operations, described below.

		An alter column operation may contain multiple sub-operations. For example, a single alter column operation may rename a column, change its type, and add a check constraint.
		An alter column operation may contain multiple sub-operations. For example, a single alter column operation may change its type, and add a check constraint.