@bradleyayers/node-pg-migrate v2.3.0

pg-migrate

Node.js database migration management built exclusively for postgres.

Installation

$ npm install node-pg-migrate

Installing this module adds a runnable file into your node_modules/.bin directory. If installed globally (with the -g option), you can run pg-migrate and if not, you can run ./node_modules/.bin/pg-migrate

Usage

You can specify your database connection information using config.

// config/default.json
{
  "db": "postgres://postgres:password@localhost:5432/name"
}

or

// config/default.json
{
  "db": {
    "user": "postgres",
    "password": "",
    "host": "localhost",
    "port": 5432,
    "name": "name"
  }
}

You could also specify your database url by setting the environment variable DATABASE_URL.

DATABASE_URL=postgres://postgres@localhost/name node-pg-migrate

You can specify custom JSON file with config (format is same as for db entry of config file)

If a .env file exists, it will be loaded using dotenv (if installed) when running the pg-migrate binary.

Depending on your project's setup, it may make sense to write some custom grunt tasks that set this env var and run your migration commands. More on that below.

The following are the available commands:

• pg-migrate create {migration-name} - creates a new migration file with the name you give it. Spaces and underscores will be replaced by dashes and a timestamp is prepended to your file name.
• pg-migrate up - runs all up migrations from the current state.
• pg-migrate up {N} - runs N up migrations from the current state.
• pg-migrate down - runs a single down migration.
• pg-migrate down {N} - runs N down migrations from the current state.
• pg-migrate unlock - unlocks migrations (if previous up/down migration failed and was not automatically unlocked).

Configuration

You can adjust defaults by passing arguments to pg-migrate:

• config-file (f) - The file with migration JSON config (defaults to undefined)
• schema (s) - The schema on which migration will be run (defaults to public)
• database-url-var (d) - Name of env variable with database url string (defaults to DATABASE_URL)
• migrations-dir (m) - The directory containing your migration files (defaults to migrations)
• migrations-schema - The schema storing table which migrations have been run (defaults to same value as schema)

• migrations-table (t) - The table storing which migrations have been run (defaults to pgmigrations)

• check-order - Check order of migrations before running them (defaults to true, to switch it off supply --no-check-order on command line). (There should be no migration with timestamp lesser than last run migration.)

See all by running pg-migrate --help.

Most of configuration options can be also specified in config file.

For SSL connection to DB you can set PGSSLMODE environment variable to value from list other then disable. e.g. PGSSLMODE=require pg-migrate up (pg will take it into account)

JSON Configuration

You can use config or your own json file with configuration (config-file command line option).

Available options are:

• migrations-dir, migrations-schema, migrations-table, check-order - same as above

• either url or user, password, host (defaults to localhost), port (defaults to 5432), name - for connection details

• type-shorthands - for column type shorthands

  You can specify custom types which will be expanded to column definition (e.g. for module.exports = { "type-shorthands": { id: { type: 'uuid', primaryKey: true }, createdAt: { type: 'timestamp', notNull: true, default: new require('node-pg-migrate').PgLiteral('current_timestamp') } } } it will in pgm.createTable('test', { id: 'id', createdAt: 'createdAt' }); produce SQL CREATE TABLE "test" ("id" uuid PRIMARY KEY, "createdAt" timestamp DEFAULT current_timestamp NOT NULL);).

Locking

pg-migrate automatically checks if no other migration is running. To do so, it locks the migration table and enters comment there. There are other options how to do it, but I choose this one (see #88). In some circumstances it is possible that lock will not be released (Error message - Error: Unable to fetch migrations: Error: Another migration is already running). In that case you need to run pg-migrate unlock to release the lock again.

Defining Migrations

When you run pg-migrate create a new migration file is created that looks like this:

exports.up = function up(pgm) {

}
exports.down = function down(pgm) {

}

pgm is a helper object that provides migration operations and run is the callback to call when you are done.

IMPORTANT Calling the migration functions on pgm doesn't actually migrate your database. These functions just add sql commands to a stack that is run.

Automatic Down Migrations

If exports.down is not present in a migration, pg-migrate will try to automatically infer the operations that make up the down migration by reversing the operations of the up migration. Only some operations have automatically inferrable equivalents (details below on each operation). Sometimes, migrations are destructive and cannot be rolled back. In this case, you can set exports.down = false to tell pg-migrate that the down migration is impossible.

Async Migrations

In some cases, you may want to perform some async operation during a migration, for example fetching some information from an external server, or inserting some data into the database. To make a migration block operate in async mode, just add another callback argument to the function signature. However, be aware that NONE of the pgm operations will be executed until run() is called. Here's an example:

exports.up = function up(pgm, run) {
  doSomethingAsync(function() {
    run();
  });
}

Another way how to perform some async operation is to return Promise from up or down function. Example:

exports.up = function(pgm) {
  return new Promise(resolve => {
    // doSomethingAsync
    resolve();
  });
}

Migration methods

The pgm object that is passed to each up/down block has many different operations available. Each operation is simply a function that generates some sql and stores it in the current pgm context.

By default, each migration will be run in a transaction. To disable transactions for a specific migration, call pgm.noTransaction() This is required for some SQL operations that cannot be run within a transaction. It should be used carefully.

Creating & Altering Tables / Columns

pgm.createTable( tablename, columns, options )

Create a new table - postgres docs

Arguments:

• tablename string - name for the new table
• columns object - column names / options -- see column definitions section
• options object - table options (optional)
  • inherits string - table to inherit from

Reverse Operation: dropTable

pgm.dropTable( tablename )

Drop existing table - postgres docs

Arguments:

• tablename string - name of the table to drop

pgm.renameTable( tablename, new_tablename )

Rename a table - postgres docs

Arguments:

• tablename string - name of the table to rename
• new_table object - new name of the table

Reverse Operation: same operation in opposite direction

pgm.addColumns( tablename, new_columns )

Add columns to an existing table - postgres docs

Arguments:

• tablename string - name of the table to alter
• new_columns object - column names / options -- see column definitions section

Aliases: addColumn Reverse Operation: dropColumns

pgm.dropColumns( tablename, columns )

Drop columns from a table - postgres docs

Arguments:

• tablename string - name of the table to alter
• columns array of strings or object - columns to drop (if object, uses keys)

Aliases: dropColumn

pgm.renameColumn( tablename, old_column_name, new_column_name )

Rename a column - postgres docs

Arguments:

• tablename string - name of the table to alter
• old_column_name string - current column name
• new_column_name string - new column name

Reverse Operation: same operation in opposite direction

pgm.alterColumn( tablename, column_name, column_options )

Alter a column (default value, type, allow null) - postgres docs

Arguments:

• tablename string - name of the table to alter
• column_name string - column to alter
• column_options object - optional new column options
  • default string or null - null, string
  • type string - new datatype
  • notNull boolean - sets NOT NULL if true

pgm.addConstraint( tablename, constraint_name, expression )

Add a named column constraint - postgres docs

Arguments:

• tablename string - name of the table to alter
• constraint_name string - name for the constraint
• expression string - constraint expression (raw sql)

Aliases: createConstraint Reverse Operation: dropConstraint

pgm.dropConstraint( tablename, constraint_name )

Drop a named column constraint - postgres docs

Arguments:

• tablename string - name of the table to alter
• constraint_name string - name for the constraint

pgm.createIndex( tablename, columns, options )

Create a new index - postgres docs

Arguments:

• tablename string - name of the table to alter
• columns string or array of strings - columns to add to the index
• options index options - optional options:
  • name string - name for the index (one will be inferred from table/columns if undefined)
  • unique boolean - set to true if this is a unique index
  • where string - raw sql for where clause of index
  • concurrently boolean - create this index concurrently
  • method string - btree | hash | gist | spgist | gin

Aliases: addIndex Reverse Operation: dropIndex

pgm.dropIndex( tablename, columns, options )

Drop an index - postgres docs

Arguments:

• tablename string - name of the table to alter
• columns string or array of strings - column names, used only to infer an index name
• options index options - optional options:
  • name string - name of the index to drop

Miscellaneous Operations

pgm.sql( sql )

Run raw sql -- with some optional very basic mustache templating

Arguments:

• sql string - SQL query to run
• args object - (optional) key/val of arguments to replace

pgm.func( sql )

Inserts raw string, which is not escaped

e.g. pgm.func('CURRENT_TIMESTAMP') to use in default option for column definition

Arguments:

• sql string - string to not be escaped

pgm.createExtension( extension )

Install postgres extension(s) - postgres docs

Arguments:

• extension string or array of strings - name(s) of extensions to install

Aliases: addExtension Reverse Operation: dropExtension

pgm.dropExtension( extension )

Un-install postgres extension(s) - postgres docs

Arguments:

• extension string or array of strings - name(s) of extensions to install

pgm.createType( type_name, values )

Create a new data type - postgres docs

Arguments:

• type_name string - name of the new type
• values array of strings or object if an array the contents are possible values for an enum type, if an object names and types for a composite type

Aliases: addType Reverse Operation: dropType

pgm.dropType( type_name )

Drop a custom data type - postgres docs

Arguments:

• type_name string - name of the new type

Column Definitions

The createTable and addColumns methods both take a columns argument that specifies column names and options. It is a object (key/value) where each key is the name of the column, and the value is another object that defines the options for the column.

• type string - data type (use normal postgres types)
• unique boolean - set to true to add a unique constraint on this column
• primaryKey boolean - set to true to make this column the primary key
• notNull boolean - set to true to make this column not null
• check string - sql for a check constraint for this column
• references string - a table name that this column is a foreign key to
• onDelete string - adds ON DELETE constraint for a reference column
• onUpdate string - adds ON UPDATE constraint for a reference column

Data types & Convenience Shorthand

Data type strings will be passed through directly to postgres, so write types as you would if you were writing the queries by hand.

There are some aliases on types to make things more foolproof: (int, string, float, double, datetime, bool)

There is a shorthand to pass only the type instead of an options object: pgm.addColumns('myTable', { age: 'integer' }); is equivalent to pgm.addColumns('myTable', { age: { type: 'integer' } });

There is a shorthand for normal auto-increment IDs: pgm.addColumns('myTable', { id: 'id' }); is equivalent to pgm.addColumns('myTable', { id: { type: 'serial', primaryKey: true } });

Using schemas

Instead of passing string as name to pgm functions, you can pass an object with keys schema and name. E.g.

pgm.createTable( {schema: 'my_schema', name: 'my_table_name'}, {id: 'serial'});

will generate

CREATE TABLE "my_schema"."my_table_name" (
 "id" serial
);

Explanation & Goals

Why only Postgres? - By writing this migration tool specifically for postgres instead of accommadating many databases, we can actually provide a full featured tool that is much simpler to use and maintain. I was tired of using crippled database tools just in case one day we switch our database.

Async / Sync - Everything is async in node, and that's great, but a migration tool should really just be a fancy wrapper that generates SQL. Most other migration tools force you to bring in control flow libraries or wrap everything in callbacks as soon as you want to do more than a single operation in a migration. Plus by building up a stack of operations, we can automatically infer down migrations (sometimes) to save even more time.

Naming / Raw Sql - Many tools force you to use their constants to do things like specify data types. Again, this tool should be a fancy wrapper that generates SQL, so whenever possible, it should just pass through user values directly to the SQL. The hard part is remembering the syntax of the specific operation, not remembering how to type "timestamp"!