wheels generate migration

Generate database migration files using templates.

Synopsis

wheels generate migration name=<migrationName> [options]

# Can also be used as:
wheels g migration name=<migrationName> [options]

CommandBox Parameter Syntax

• Named parameters: param=value (e.g., name=CreateUsersTable, table=users)

• Flag parameters: --flag equals flag=true (e.g., --force equals force=true)

• Param with value: --param=value equals param=value (e.g., --description="User management")

Recommended: Use named parameters: wheels generate migration name=CreateUsersTable --create=users

Description

The wheels generate migration command creates database migration files using pre-built templates. Migrations provide version control for your database schema, allowing you to incrementally modify your database structure and roll back changes when needed. The command intelligently detects migration type from the name pattern and uses appropriate templates with transaction handling and error management.

Arguments

Argument	Description	Default
name	Migration name (e.g., CreateUsersTable, AddEmailToUsers)	Required

Migration Name Conventions

• Must start with a letter

• Can contain letters, numbers, and underscores

• Use PascalCase for readability

• Should describe the migration action clearly

Common Patterns:

• Create[Table]Table - Creates a new table

• Add[Column]To[Table] - Adds column(s) to existing table

• Remove[Column]From[Table] - Removes column(s) from table

• Rename[OldColumn]To[NewColumn] - Renames a column

• Change[Column]In[Table] - Modifies column type/properties

• CreateIndexOn[Table] - Adds an index

• RemoveIndexFrom[Table] - Removes an index

Options

Option	Description	Valid Values	Default
create	Table name to create (forces create_table type)	Valid table name	""
table	Table name to modify (for column operations)	Valid table name	""
drop	Table name to drop (forces remove_table type)	Valid table name	""
description	Migration description (added as hint)	Any descriptive text	""
force	Overwrite existing migration file	true, false	false

Migration Types and Templates

The command automatically detects the migration type and uses the appropriate template:

Type	Template	Detected Pattern	Example
Create Table	create-table.txt	Create*Table	CreateUsersTable
Remove Table	remove-table.txt	Drop*Table, Remove*Table	DropUsersTable
Add Column	create-column.txt	Add*To*	AddEmailToUsers
Remove Column	remove-column.txt	Remove*From*	RemoveAgeFromUsers
Change Column	change-column.txt	Change*In*	ChangeNameInUsers
Rename Column	rename-column.txt	Rename*To*	RenameFirstnameToFullname
Add Index	create-index.txt	CreateIndexOn*	CreateIndexOnUsersEmail
Remove Index	remove-index.txt	RemoveIndexFrom*	RemoveIndexFromUsers
Blank	blank.txt	Any other pattern	CustomMigration

Examples

Create Table Migration

wheels generate migration name=CreateUsersTable

Creates migration using create-table.txt template with transaction handling.

Create Table with Explicit Table Name

wheels generate migration name=CreateUsersTable --create=users

Forces create_table type and uses "users" as table name.

Add Column Migration

wheels generate migration name=AddEmailToUsers --table=users

Creates migration using create-column.txt template.

Remove Column Migration

wheels generate migration name=RemoveAgeFromUsers --table=users

Creates migration using remove-column.txt template.

Drop Table Migration

wheels generate migration name=DropProductsTable

Creates migration using remove-table.txt template.

With Description

wheels generate migration name=CreateUsersTable --description="User authentication table"

Adds description as hint to the migration component.

Blank/Custom Migration

wheels generate migration name=MigrateUserData --description="Move user data to new structure"

Creates blank migration for custom migration code.

Force Overwrite

wheels generate migration name=CreateUsersTable --force=true

Overwrites existing migration file.

Generated Code Examples

Create Table Migration (Using Template)

component extends="wheels.migrator.Migration" hint="CreateUsersTable" {

	function up() {
		transaction {
			try {
				t = createTable(name = 'users', force='false', id='true', primaryKey='id');
				t.timestamps();
				t.create();
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

	function down() {
		transaction {
			try {
				dropTable('users');
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

}

Add Column Migration (Using Template)

component extends="wheels.migrator.Migration" hint="AddEmailToUsers" {

	function up() {
		transaction {
			try {
				addColumn(table='users', columnType='string', columnName='column_name', default='', null='true', limit='255');
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

	function down() {
		transaction {
			try {
				removeColumn(table='users', columnName='column_name');
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

}

Blank Migration (Using Template)

component extends="wheels.migrator.Migration" hint="MigrateUserData" {

	function up() {
		transaction {
			try {
				// your code goes here
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

	function down() {
		transaction {
			try {
				// your code goes here
			} catch (any e) {
				local.exception = e;
			}

			if (StructKeyExists(local, "exception")) {
				transaction action="rollback";
				Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
			} else {
				transaction action="commit";
			}
		}
	}

}

Smart Name Detection

The command infers table names from migration name patterns:

Pattern Detection Examples

Migration Name	Detected Type	Inferred Table	Template Used
CreateUsersTable	create_table	users	create-table.txt
DropProductsTable	remove_table	products	remove-table.txt
AddEmailToUsers	create_column	users	create-column.txt
RemoveAgeFromUsers	remove_column	users	remove-column.txt
RenameFirstnameToFullname	rename_column	(needs --table)	rename-column.txt
ChangeStatusInOrders	change_column	orders	change-column.txt
CreateIndexOnUsersEmail	create_index	users	create-index.txt
CustomDataMigration	blank	N/A	blank.txt

Template System

All migrations use templates from /cli/src/templates/dbmigrate/:

Available Templates

• blank.txt - Empty migration with transaction wrapper

• create-table.txt - Create table with timestamps

• remove-table.txt - Drop table with reversible down()

• create-column.txt - Add column with options

• remove-column.txt - Remove column

• change-column.txt - Modify column type/properties

• rename-column.txt - Rename column

• create-index.txt - Add index to table

• remove-index.txt - Remove index from table

Template Customization

You can override default templates by placing custom versions in /app/snippets/dbmigrate/:

# Copy template to customize
cp cli/src/templates/dbmigrate/create-table.txt app/snippets/dbmigrate/create-table.txt

# Edit your custom template
# Wheels will automatically use your version

Template Variables

Templates use placeholder variables that are replaced during generation:

Variable	Description	Example
|DBMigrateDescription|	Migration hint/description	CreateUsersTable
|tableName|	Table name	users
|columnName|	Column name	email
|columnType|	Column type	string
|force|	Force table creation	false
|id|	Auto-create ID column	true
|primaryKey|	Primary key name	id
|allowNull|	Allow NULL values	true
|limit|	Column length limit	255
|default|	Default value	""
|unique|	Unique index	false

Migration Workflow

1. Generate Migration

wheels generate migration name=CreateUsersTable

2. Edit Migration File

# File created at: /app/migrator/migrations/20250119123045_CreateUsersTable.cfc

Add columns to the migration:

function up() {
    transaction {
        try {
            t = createTable(name = 'users', force='false', id='true', primaryKey='id');
            t.string(columnNames='firstName,lastName', allowNull=false);
            t.string(columnNames='email', allowNull=false, limit=100);
            t.boolean(columnNames='active', default=true);
            t.timestamps();
            t.create();

            // Add index on email
            addIndex(table='users', columnNames='email', unique=true);
        } catch (any e) {
            local.exception = e;
        }

        if (StructKeyExists(local, "exception")) {
            transaction action="rollback";
            Throw(errorCode = "1", detail = local.exception.detail, message = local.exception.message, type = "any");
        } else {
            transaction action="commit";
        }
    }
}

3. Check Migration Status

wheels dbmigrate info

4. Run Migration

wheels dbmigrate latest

5. Rollback if Needed

wheels dbmigrate down

Column Types

Common column types available in migrations:

Method	Database Type	Example
t.string()	VARCHAR(255)	t.string(columnNames='email')
t.text()	TEXT	t.text(columnNames='bio')
t.integer()	INTEGER	t.integer(columnNames='age')
t.biginteger()	BIGINT	t.biginteger(columnNames='views')
t.decimal()	DECIMAL	t.decimal(columnNames='price', precision=10, scale=2)
t.float()	FLOAT	t.float(columnNames='rating')
t.boolean()	BOOLEAN	t.boolean(columnNames='active')
t.date()	DATE	t.date(columnNames='birthdate')
t.datetime()	DATETIME	t.datetime(columnNames='registeredAt')
t.time()	TIME	t.time(columnNames='startTime')
t.binary()	BLOB	t.binary(columnNames='avatar')
t.timestamps()	DATETIME	Creates createdAt and updatedAt

Best Practices

1. Descriptive Names: Use clear, action-oriented migration names

2. One Change Per Migration: Keep migrations focused on single changes

3. Always Include down(): Make migrations reversible when possible

4. Use Transactions: Templates include transactions by default

5. Test Rollbacks: Always test down() method works correctly

6. Index Performance Columns: Add indexes on frequently queried columns

7. Document Complex Migrations: Use description parameter for clarity

8. Avoid Data in Migrations: Keep migrations schema-only when possible

Common Patterns

Create Table with Relationships

function up() {
    transaction {
        try {
            t = createTable(name = 'posts', force='false', id='true');
            t.string(columnNames='title', allowNull=false);
            t.text(columnNames='content');
            t.references(name='userId', references='users');
            t.boolean(columnNames='published', default=false);
            t.timestamps();
            t.create();

            addIndex(table='posts', columnNames='userId');
        } catch (any e) {
            local.exception = e;
        }
        // Transaction handling...
    }
}

Add Multiple Columns

function up() {
    transaction {
        try {
            addColumn(table='users', columnType='string', columnName='phoneNumber', limit=20);
            addColumn(table='users', columnType='boolean', columnName='emailVerified', default=false);
            addColumn(table='users', columnType='datetime', columnName='lastLoginAt');

            addIndex(table='users', columnNames='phoneNumber');
        } catch (any e) {
            local.exception = e;
        }
        // Transaction handling...
    }
}

Data Migration

function up() {
    transaction {
        try {
            // Add new column
            addColumn(table='users', columnType='string', columnName='fullName');

            // Migrate data (use with caution)
            execute("UPDATE users SET fullName = CONCAT(firstName, ' ', lastName)");

            // Remove old columns
            removeColumn(table='users', columnName='firstName');
            removeColumn(table='users', columnName='lastName');
        } catch (any e) {
            local.exception = e;
        }
        // Transaction handling...
    }
}

Error Handling

Migration Already Exists

wheels generate migration name=CreateUsersTable
# Error: Migration file already exists. Use force=true to overwrite.

# Solution:
wheels generate migration name=CreateUsersTable --force=true

Invalid Migration Name

wheels generate migration name="Create Users Table"
# Error: Invalid migration name. Use only letters, numbers, and underscores.

# Solution:
wheels generate migration name=CreateUsersTable

Migration Fails to Run

wheels dbmigrate latest
# Error during migration execution

# Check the migration file for syntax errors
# Review database logs
# Test the down() method
wheels dbmigrate down

Template Benefits

Using templates provides several advantages:

Transaction Safety - All operations wrapped in transactions Error Handling - Automatic try/catch with rollback Consistency - Same structure across all migrations Best Practices - Templates follow Wheels conventions Customizable - Override templates in /app/snippets/ Maintainability - Centralized template updates

See Also

• wheels dbmigrate latest - Run migrations

• wheels dbmigrate info - Check migration status

• wheels dbmigrate create table - Alternative table creation

• wheels dbmigrate create blank - Alternative blank migration

• wheels generate model - Generate models

• Database Migrations Guide - Migration best practices

• Template System Guide - Customize templates