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A Common DSL for Migrating Databases

Create a Table

create_table("users") {
  t.Column("id", "integer", {primary: true})
  t.Column("email", "string", {})
  t.Column("twitter_handle", "string", {"size": 50})
  t.Column("age", "integer", {"default": 0})
  t.Column("admin", "bool", {"default": false})
  t.Column("company_id", "uuid", {"default_raw": "uuid_generate_v1()"})
  t.Column("bio", "text", {"null": true})
  t.Column("joined_at", "timestamp", {})
  t.Index("email", {"unique": true})

create_table("todos") {
  t.Column("user_id", "integer", {})
  t.Column("title", "string", {"size": 100})
  t.Column("details", "text", {"null": true})
  t.ForeignKey("user_id", {"users": ["id"]}, {"on_delete": "cascade"})

The id column don't have to be an integer. For instance, your can use an UUID type instead:

create_table("users") {
  t.Column("id", "uuid", {primary: true})
  // ...

By default, fizz will generate two timestamp columns: created_at and updated_at.

The t.Columns method takes the following arguments: name of the column, the type of the field, and finally the last argument is any options you want to set on that column.

"Common" Types:

  • string
  • text
  • timestamp, time, datetime
  • integer
  • bool
  • uuid

Any other type passed it will be be passed straight through to the underlying database.

For example for PostgreSQL you could pass jsonband it will be supported, however, SQLite will yell very loudly at you if you do the same thing!

Supported Options:

  • size - The size of the column. For example if you wanted a varchar(50) in Postgres you would do: t.Column("column_name", "string", {"size": 50})
  • null - By default columns are not allowed to be null.
  • default - The default value you want for this column. By default this is null.
  • default_raw - The default value defined as a database function.
  • after - (MySQL Only) Add a column after another column in the table. example: {"after":"created_at"}
  • first - (MySQL Only) Add a column to the first position in the table. example: {"first": true}

Composite primary key

create_table("user_privileges") {
	t.Column("user_id", "int")
	t.Column("privilege_id", "int")
	t.PrimaryKey("user_id", "privilege_id")

Please note that the t.PrimaryKey statement MUST be after the columns definitions.

Drop a Table


Rename a Table

rename_table("old_table_name", "new_table_name")

Add a Column

add_column("table_name", "column_name", "string", {})

See above for more details on column types and options.

Alter a column

change_column("table_name", "column_name", "string", {})

Rename a Column

rename_column("table_name", "old_column_name", "new_column_name")

Drop a Column

drop_column("table_name", "column_name")

Add an Index

Supported Options:

  • name - This defaults to table_name_column_name_idx
  • unique

Simple Index:

add_index("table_name", "column_name", {})

Multi-Column Index:

add_index("table_name", ["column_1", "column_2"], {})

Unique Index:

add_index("table_name", "column_name", {"unique": true})

Index Names:

add_index("table_name", "column_name", {}) # name => table_name_column_name_idx
add_index("table_name", "column_name", {"name": "custom_index_name"})

Rename an Index

rename_index("table_name", "old_index_name", "new_index_name")

Drop an Index

drop_index("table_name", "index_name")

Add a Foreign Key

add_foreign_key("table_name", "field", {"ref_table_name": ["ref_column"]}, {
    "name": "optional_fk_name",
    "on_delete": "action",
    "on_update": "action",

Supported Options

  • name - This defaults to table_name_ref_table_name_ref_column_name_fk
  • on_delete - CASCADE, SET NULL, ...
  • on_update

Note: on_update and on_delete are not supported on CockroachDB yet.

Drop a Foreign Key

drop_foreign_key("table_name", "fk_name", {"if_exists": true})

Supported Options

  • if_exists - Adds IF EXISTS condition


sql("select * from users;")

Execute an External Command

Sometimes during a migration you need to shell out to an external command.

exec("echo hello")



To run end-to-end tests, use

make test

If you made changes to the end-to-end tests and want to update the fixtures, run the following command a couple of times until tests pass:

REFRESH_FIXTURES=true make test

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