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https://github.com/blainehansen/postgres_migrator

A postgres migration generator and runner that uses raw declarative sql.
https://github.com/blainehansen/postgres_migrator

database database-migrations migration migrations postgres raw-sql rust

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A postgres migration generator and runner that uses raw declarative sql.

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# `postgres_migrator`



`postgres_migrator` allows you to write your postgres schema directly in *declarative sql*, to automatically generate migrations when you change that declarative schema, and to apply those migrations with rigorous version tracking and consistency checks.



**No more orms!** Use the full power of postgres directly without having to manually write migrations.



`postgres_migrator` is able to:



- Automatically generate raw sql migrations by diffing the sql in a migrations folder to that in a schema folder.

- Apply those migrations and save migration version numbers in the database, so you can know what state a database is supposed to be in.

- Run consistency checks on migrations, so that they are only ever applied in the order they were generated. This can prevent very painful debugging and database corruption.



`postgres_migrator` intentionally doesn't do the following:



- Create "down" versions of migrations. If you want to undo something in production, just make a new migration (that's best practice anyway). In dev just force the database into the right state.

- Allow running migrations only up to a certain version. `postgres_migrator` will always apply all available unapplied migrations. If you don't want to apply some migrations, move them to a different folder or change their extension to something other than `.sql`.

- Figure out database diffs itself, but instead uses the well-establised [`migra`](https://github.com/djrobstep/migra) under the hood.



# Example



If your `schema` directory contains a sql file like this:



```sql

create table fruit (

  id serial primary key,

  name text not null unique,

  color text not null default ''

);

```



Then running `postgres_migrator generate 'add fruit table'` will generate a migration called `$new_version.$previous_version.add_fruit_table.sql` in the `migrations` folder.



You can then run `postgres_migrator migrate` to run this migration (and any others that haven't been run).



If you then change your schema sql to this:



```sql

create type flavor_type as enum('SWEET', 'SAVORY');



create table fruit (

  id serial primary key,

  name text not null unique,

  flavor flavor_type not null default 'SWEET'

);

```



Then running `postgres_migrator generate 'remove color add flavor'` will generate `$new_version.$previous_version.remove_color_add_flavor.sql` that will go from the previous state to the new state.



# Usage



First, place your declarative sql files in the `schema` directory and create a directory for migrations called `migrations`. You can customize these with `--schema-directory` and `--migrations-directory`.



## As a standalone docker image



`postgres_migrator` is distributed as a docker image, `blainehansen/postgres_migrator`. You can run it using `docker run`, and since the cli needs to interact with a postgres database, read schema files, and read/write migration files, it needs quite a few options:



```bash

docker run --rm -it --network host -u $(id -u ${USER}):$(id -g ${USER}) -v $(pwd):/working blainehansen/postgres_migrator 

```



To make this easier to manage, you can package that command in a function, alias, or script:



```bash

function postgres_migrator {

  local result=$(docker run --rm -it --network host -u $(id -u ${USER}):$(id -g ${USER}) -v $(pwd):/working -e PG_URL=$PG_URL blainehansen/postgres_migrator "$@")

  echo $result

  return $?

}



# or

alias postgres_migrator="docker run --rm -it --network host -u $(id -u ${USER}):$(id -g ${USER}) -v $(pwd):/working -e PG_URL=$PG_URL blainehansen/postgres_migrator"



# or in it's own executable file

docker run --rm -it --network host -u $(id -u ${USER}):$(id -g ${USER}) -v $(pwd):/working -e PG_URL=$PG_URL blainehansen/postgres_migrator "$@"



# now you can call it more cleanly

postgres_migrator generate 'adding users table'

postgres_migrator migrate

```



## With docker compose



Many people run postgres as one service in a docker compose setup, either using a `postgres` image or something like `cloud-sql-proxy`.



```yml

version: '3'

services:

  postgres_migrator:

    image: blainehansen/postgres_migrator

    container_name: postgres_migrator

    depends_on:

      - db

    environment:

      - PG_URL=postgres://experiment_user:asdf@db:5432/experiment_db?sslmode=disable

    volumes:

      - .:/working/

    tty: true

    entrypoint: tail -F anything



  db:

    image: postgres:alpine

    container_name: db

    environment:

      - POSTGRES_DB=experiment_db

      - POSTGRES_USER=experiment_user

      - POSTGRES_PASSWORD=asdf

    ports:

      - "5432:5432"

    command: postgres -c 'max_wal_size=2GB'

```



If that is running, a command like this should work:



```sh

docker exec -it -u $(id -u ${USER}):$(id -g ${USER}) postgres_migrator postgres_migrator migrate

```



## As a Rust binary



This package is published to [crates.io](https://crates.io/crates/postgres_migrator), so you can use `cargo install postgres_migrator` to install it.



The package calls the [`migra`](https://github.com/djrobstep/migra) command, so that must be installed and runnable.



---



Cli usage:



```

USAGE:

    postgres_migrator [OPTIONS] --pg-url  



OPTIONS:

    -h, --help

            Print help information



        --pg-url 

            postgres connection string, in the form postgres://user:password@host:port/database

            can also be loaded from the environment variable PG_URL [env: PG_URL=]



        --migrations-directory 

            directory where migrations are stored [default: migrations]



        --schema-directory 

            directory where the declarative schema is located [default: schema]



    -V, --version

            Print version information



SUBCOMMANDS:

    generate    generate new migration and place in migrations folder

    migrate     apply all migrations to database

    check       checks that `source` and `target` are in sync, throws error otherwise

    diff        prints out the sql diff necessary to convert `source` to `target`

    compact     ensure both database and migrations folder are current with schema and compact

                to only one migration

    clean       cleans the current instance of all temporary databases

    help        Print this message or the help of the given subcommand(s)

```



## What is `compact`?



Over time a migrations folder can get large and unwieldy, with possibly hundreds of migrations. This long log gets less and less useful over time, especially for small teams. The `compact` command replaces all migrations with a single migration that creates the entire schema at once.



Some teams will consider this dangerous and unnecessary, and they're free to not use it!



# Credits



- [`migra`](https://github.com/djrobstep/migra) for making it possible to diff schemas.

- [`tusker`](https://github.com/bikeshedder/tusker) was the inspiration for using temporary databases as diff targets. `postgres_migrator` adds the ability to generate and run versioned migrations and to perform compaction.

- Thank you [Rust](https://www.rust-lang.org/) for being so awesome! [clap](https://github.com/clap-rs/clap) and [rust-postgres](https://github.com/sfackler/rust-postgres) in particular made this way easier.



# Contributing



Pull requests to make the script more ergonomic or robust are welcome.