Database.Persist.Migration.Core

Defines a migration framework for the persistent library.

Documentation

type Version = Int

The version of a database. An operation migrates from the given version to another version.

The version must be increasing, such that the lowest version is the first version and the highest version is the most up-to-date version.

A version represents a version of the database schema. In other words, any set of operations taken to get to version X *MUST* all result in the same database schema.

type OperationPath = (Version, Version)

The path that an operation takes.

(~>) :: Version -> Version -> OperationPath

An infix constructor for OperationPath.

type Migration = [MigrationPath]

A migration list that defines operations to manually migrate a database schema.

data MigrationPath

A path representing the operations needed to run to get from one version of the database schema to the next.

Constructors

OperationPath := [Operation]

Instances

Show MigrationPath

Defined in Database.Persist.Migration.Core

Methods

showsPrec :: Int -> MigrationPath -> ShowS

show :: MigrationPath -> String

showList :: [MigrationPath] -> ShowS

opPath :: MigrationPath -> OperationPath

Get the OperationPath in the MigrationPath.

newtype MigrateSettings

Settings to customize migration steps.

Constructors

MigrateSettings

Fields

• versionToLabel :: Version -> Maybe String

  A function to optionally label certain versions

defaultSettings :: MigrateSettings

Default migration settings.

validateMigration :: Migration -> Either String ()

Validate the given migration.

runMigration :: MonadIO m => MigrateBackend -> MigrateSettings -> Migration -> SqlPersistT m ()

Run the given migration. After successful completion, saves the migration to the database.

getMigration :: MonadIO m => MigrateBackend -> MigrateSettings -> Migration -> SqlPersistT m [MigrateSql]

Get the SQL queries for the given migration.