@nextcode/pg-migrator

Postgres Migrator

Migrations for Postgres.

Whats different in this package compared to most others?

• This package has 0 dependencies - just postgres (pg) itself as peer dependency
• Support of parallel migrations when the dependent migrations are defined
• Ships with TypeScript types, commonJs (.js) and module exports (.mjs)
• Can be called by CLI or by programmatic access

CLI

Getting Help

pg-migrator help

Lists all commands.

pg-migrator <command> help

Lists command details and parameters.

Parameters

All commands with Database interactions allow all of the following Environment variables:

• PGHOST Host of postgres server
• PGPORT Port of postgres server
• PGUSER Username of postgres user
• PGPASSWORD Password of postgres user
• PGDATABASE Database Name

All commands use the migrations folder to locate migrations. This can be changed with the -f or the --folder parameter.

The commands up and down also provide parameters to select a single migrations.

Use -n or --name to select migration by passing full filename without extension. You can also use -v or --version to select migration by version (first part of filename).

Create Migrations

Creates a new migration file prefixed with current timestamp to the migrations folder. You can pass a different folder with the -f or --folder parameter.

pg-commander create <name>

### Migrate

Applies all pending migrations. The migrations will be applied in the order of the version numbers ascending.

pg-migrator migrate

Applies/Rolls back just the selected migration.

pg-migrator up

pg-migrator down

Create / Drop Database

Tries to create or drop the database.

pg-migrator createDatabase

pg-migrator dropDatabase

Drop Table

Drops the migration table from the database.

pg-migrator dropTable

Programmatic Access

Migration

A migration is an object with the keys version, parent, up and down. The version is a string which identifies the migration. The migrator saves these in a separate table to check if an migration is already applied.

The methods up and down are async methods with the migration logic. Both need to be present, but can be empty if not needed. up contains the logic to apply the migration while down contains the logic to undo the changed of the migration.

When up method creates a new table the method down should drop the table.

Migrations will be applied in the order as they are passed. Each migration will wait until the previous is done, except you add the parent attribute.

parent is a array of version strings. The migrator will wait for all versions named there to be finished. But once all dependent migrations are done the migration will run instantly parallel to other migrations where all dependent migrations are applied. The migration will be applied instantly when parent is an empty array.

const migration = [
  version: '201812312359',
  async up(client) {
    // ...
  },
  async down(client) {
    // ...
  },
]

Create Migrator

The Migrator creates a table

// constructor(tableName?: string = 'migrations', poolConfig?: PoolConfig)
const migrator = new Migrator();

// migrate(migrations: Migration[]);
migrator.migrate([
  migration1,
  migration2,
  //...
]);

Migrate

Pass an array of migrations and the migrator will skip all migrations which were already applied. Pending migrations will be applied in parallel - if possible - depending on the dependent migrations.

// constructor(tableName?: string = 'migrations', poolConfig?: PoolConfig)
const migrator = new Migrator();

// migrate(migrations: Migration[]);
migrator.migrate([
  migration1,
  migration2,
  //...
]);

Up / Down

Pass an single migration and the will apply or undo the migration depending on the current status of the migration.

// constructor(tableName?: string = 'migrations', poolConfig?: PoolConfig)
const migrator = new Migrator();

// up(migration: Migration);
// down(migration: Migration);
migrator.up(migration);
migrator.down(migration);

Create / Drop Database

The migrator also supports to create or drop a new database. The command will check if the database is already existing and skip creation if database already exists. On the other hand the drop of the database will be skipped when database is not existing.

// constructor(tableName?: string = 'migrations', poolConfig?: PoolConfig)
const migrator = new Migrator();

// createDatabase();
// dropDatabase();
migrator.createDatabase();
migrator.dropDatabase();

Drop Table

Once a migration is applied the migrator will create a table to save the applied migrations. This table can be dropped with the dropTable command.

// constructor(tableName?: string = 'migrations', poolConfig?: PoolConfig)
const migrator = new Migrator();

// dropTable();
migrator.dropTable();

Changelog

See history for more details.

• 1.0.0 2018-xx-xx Initial release