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Sqlow

pronounced Squallow - a mix of Swallow (the migratory bird) and SQL

A CLI database schema migrator that doesn't care about versions.

Supported databases:

  • MariaDB / Mysql
  • PostgreSQL

Installation

From Package Manager

Snap

sudo snap install sqlow

Homebrew

brew tap dosaki/sqlow
brew install sqlow

From github releases

sys_type=$(uname -s | tr '[:upper:]' '[:lower:]')
sys_arch=$(uname -m | tr '[:upper:]' '[:lower:]')
if [[ $sys_arch == "x86_64" ]]; then
  sys_arch="amd64"
fi
curl -LJ https://github.com/dosaki/sqlow/releases/latest/download/$sys_type-$sys_arch.zip -o sqlow.zip && unzip sqlow.zip
./sqlow --help # verify that it works

From source

git clone [email protected]:dosaki/sqlow.git
cd sqlow
./build.sh --default --no-zip --output=./dist
./dist/sqlow --help # verify that it works

Usage

Create a file like below:

# migration.yml

migrations:
  - description: Ensure that description exists for task_types
    check: SELECT description FROM task_types;
    onFail:
      - ALTER TABLE task_types ADD COLUMN description VARCHAR(1023);
      - UPDATE task_types SET description = CONCAT('Task type for ', name);
      - ALTER TABLE task_types ALTER COLUMN description SET NOT NULL;

Then run it!

sqlow -pSup4rS@f3P@ssw0rd run ./migration.yml

You can also check which migrations are run*:

sqlow -pSup4rS@f3P@ssw0rd --dry-run run ./migration.yml

* Dry-runs work by running everything under a transaction that is then rolled back. This does not work for MariaDB (Why?) or MySQL (Why?).

Migration files

A valid migration file must start with migrations: with an array of migrations defined under it, like so:

migrations:
  - description: What this migration is meant to do
    check: your pass/fail SQL here
    onFail: sql to run if check fails (throws any errors)
    onSuccess: sql to run if check passes
    onResults: sql to run if check has 1 or more results
    onNoResults: sql to run if check has 0 results
    always: this sql always runs
  • description is always a mandatory field.
  • For any of the onXXX fields to be valid, a check must be present
  • always will run even without a check field
  • The following fields also support a list of SQL strings:
    • check
    • onFail
    • onSuccess
    • onResults
    • onNoResults
    • always

These fields can all be used together... if that makes any sense for your scenario. If that's something you're doing, the order is as listed above.

Pointing to SQL files

You can also reference SQL files by appending File to any of the fields. E.g.:

migrations:
  - description: What this migration is meant to do
    checkFile: ./path/to/your/check.file.sql
    onFail: some additional SQL to run on fail
    onFailFile: ./path/to/your/onFail.file.sql

Note:

  • onFail will always run before onFailFile!
  • xxxFile fields can only take a single string, not a list!

What if I still want versions?

Versions might be useful if you want to run something once and never again and you might not have an easy way to check whether it's been done.

You can do it with the methods below. If this is a common scenario for you, vote on issue #2.

Actual versions

First ensure there's a table to store the info:

migrations:
  - description: Ensure there's a migrations table
    check: SELECT * FROM pg_tables WHERE schemaname = 'public' AND tablename ='migrations';
    onNoResults:
      - CREATE TABLE migrations (id int primary key, version int NOT NULL);
      - INSERT INTO migrations (id, version) VALUES (1, 0);

... and then write your migrations:

migrations:
  - description: Do something once
    check: select * from migrations where id = 1 and version < 1;
    onResults:
      - Some SQL here that you want to run once
      - UPDATE migrations SET version = 1 WHERE id = 1;
  - description: Do another thing once
    check: select * from migrations where id = 1 and version < 2;
    onResults:
      - Another SQL here that you want to run once
      - UPDATE migrations SET version = 2 WHERE id = 1;

Using something a little more descriptive

First ensure there's a table to store the info:

migrations:
  - description: Ensure there's a migrations table
    check: SELECT * FROM pg_tables WHERE schemaname = 'public' AND tablename ='migrations';
    onNoResults:
      - CREATE TABLE migrations (description varchar(255) NOT NULL);

... and then write your migrations:

migrations:
  - description: Do something once
    check: select * from migrations where description = 'Do something once';
    onNoResults:
      - Some SQL here that you want to run once
      - INSERT into migrations SET description = 'Do something once';
  - description: Do another thing once
    check: select * from migrations where description = 'Do another thing once';
    onNoResults:
      - Another SQL here that you want to run once
      - INSERT into migrations SET description = 'Do another thing once';

I prefer this way since it acts as a nice human-readable log of which single-run migrations have taken effect.

Help

Usage:
  sqlow [options] -p<password> run <path>

Options:
  -h --help                 Show this Help.
  -r --recursive            Traverse the directory structure for .yml or .yaml files.
  -d --dry-run              Print the non-check SQL statements that will be run (this will run the migrations, but will roll them back).
  -c --config=<configPath>  Path to config [default: ./config.yml].
  -e --engine=<engine>      Database engine (overrides config).
  -h --host=<host>          Database host (overrides config).
  -P --port=<port>          Database port (overrides config).
  -s --schema=<schema>      Database schema (overrides config).
  -u --username=<username>  Database username (overrides config).
  -p --password=<password>  Database password (required).
  -o --options=<opts>       Comma separated list of key:value options (merges with config).

Examples:
  sqlow -r -pSup4rS@f3P@ssw0rd run ./migrations
  sqlow -pSup4rS@f3P@ssw0rd run ./migrations/a_migration.yml
  sqlow -c ./my-config.yml -pSup4rS@f3P@ssw0rd run ./migrations/a_migration.yml
  sqlow -r -c ./my-config.yml -udbuser -pSup4rS@f3P@ssw0rd run ./migrations/

Configuration

You can configure the target database with a config file like below:

# config.yml

engine: postgres   # or maria or mysql
host: your.host    # host address
port: 12345        # port for the host
schema: sqlow      # database schema
username: sqlow    # username to connect to the database. You'll likely need something with full privileges (passwords must be provided via CLI)
options:           # any options for the connection string
  option1: value1 
  option2: value2

Notes:

  • Any CLI item will override the configurations in the file.
  • Password must be passed in via the CLI (-pSup4rS@f3P@ssw0rd)