internal

Documentation

Overview

Package internal defines common functionality available within the library.

Index

• Constants
• Variables
• func MakeFilename(version string, indirection Indirection, label string) string
• func MakeMigrationFilename(m Migration) string
• type Config
• type Direction
  • func (d Direction) String() string
• type Filename
• type Indirection
• type InfoPrinter
  • func NewJSON(w io.Writer) InfoPrinter
  • func NewTSV(w io.Writer) InfoPrinter
• type Migration
  • func ParseMigration(name Filename) (mig Migration, err error)
• type MigrationParams
  • func NewMigrationParams(name string, reversible bool, dirpath, fwdLabel, revLabel string) (out *MigrationParams, err error)
  • func (m *MigrationParams) GenerateFiles() (err error)
• type Version
  • func ParseVersion(basename string) (version Version, err error)

Constants

const (
	// TimeFormat provides a consistent timestamp layout for migrations.
	TimeFormat = "20060102150405"
)

Variables

var (
	ForwardDirections = []string{
		"forward",
		"migrate",
		"up",
	}
	ReverseDirections = []string{
		"reverse",
		"rollback",
		"down",
	}
)

Allowed names for directions in migration filenames.

var (
	ErrNotFound    = errors.New("not found")
	ErrDataInvalid = errors.New("data invalid")
)

General error values to help shape behavior.

var (
	MinVersion = time.Date(0, 1, 1, 0, 0, 0, 0, time.UTC).Format(TimeFormat)
	MaxVersion = time.Date(9999, 12, 31, 23, 59, 59, 0, time.UTC).Format(TimeFormat)
)

Some reasonable lower, upper limits for migration versions.

Functions

func MakeFilename

func MakeFilename(version string, indirection Indirection, label string) string

MakeFilename creates a filename based on the independent parts. Format: "${direction}-${version}-${label}.sql"

func MakeMigrationFilename

func MakeMigrationFilename(m Migration) string

MakeMigrationFilename converts a Migration m to a filename.

Types

type Config

type Config struct {
	PathToFiles  string `json:"path_to_files"`
	ForwardLabel string `json:"forward_label"`
	ReverseLabel string `json:"reverse_label"`
}

Config is for various runtime settings.

type Direction

type Direction uint8

Direction describes which way the change goes.

const (
	// DirUnknown is a fallback value for an undetermined direction.
	DirUnknown Direction = iota
	// DirForward is like migrate up, typically the change you want to apply to
	// the DB.
	DirForward
	// DirReverse is like migrate down; used for rollbacks. Not all changes can
	// be rolled back.
	DirReverse
)

func (Direction) String

func (d Direction) String() string

type Filename

type Filename string

Filename is just a string with a specific format to migration files. One part has a generated timestamp, one part has a direction, another has a label.

type Indirection

type Indirection struct {
	Value Direction
	Label string
}

Indirection is some glue to help determine the direction of a migration, usually from a filename with an alias for a direction.

type InfoPrinter

type InfoPrinter interface {
	PrintInfo(state string, migration Migration) error
}

InfoPrinter outputs the state of one migration.

func NewJSON

func NewJSON(w io.Writer) InfoPrinter

NewJSON constructs an InfoPrinter to write out JSON.

func NewTSV

func NewTSV(w io.Writer) InfoPrinter

NewTSV constructs an InfoPrinter to write out tab separated values.

type Migration

type Migration interface {
	Indirection() Indirection
	Label() string
	Version() Version
}

A Migration is a database change with a direction name and timestamp. Typically, a Migration with a DirForward Direction is paired with another migration of DirReverse that has the same label.

func ParseMigration

func ParseMigration(name Filename) (mig Migration, err error)

ParseMigration constructs a Migration from a Filename.

type MigrationParams

type MigrationParams struct {
	Forward    Migration
	Reverse    Migration
	Reversible bool
	Dirpath    string
}

MigrationParams collects inputs needed to generate migration files. Setting Reversible to true will generate a migration file for each direction. Otherwise, it only generates a file in the forward direction. The Directory field refers to the path to the directory with the migration files.

func NewMigrationParams

func NewMigrationParams(name string, reversible bool, dirpath, fwdLabel, revLabel string) (out *MigrationParams, err error)

NewMigrationParams constructs a MigrationParams that's ready to use.

func (*MigrationParams) GenerateFiles

func (m *MigrationParams) GenerateFiles() (err error)

GenerateFiles creates the migration files. If the migration is reversible it generates files in forward and reverse directions; otherwise it generates just one migration file in the forward direction. It closes each file handle when it's done.

type Version

type Version interface {
	Before(u Version) bool
	String() string
	Value() int64
}

Version is for comparing migrations to each other.

func ParseVersion

func ParseVersion(basename string) (version Version, err error)

ParseVersion extracts Version info from a file's basename.