Cassandra Schema

Simple reversible schema migrations for cassandra.

• Add query_delay option to configure sleep time between schema changes. Default 0.
• Add lock_retry option to retry migration if schema is locked. Default []

• Add query_timeout option for running migration commands. Default 30 seconds.
• Log relevant exception message when running migrations

• Refactor schema_information queries to use LWT and :quorum consistency level
• Implement a simple locking system to prevent concurrent migrations

CassandraSchema uses a DSL via the CassandraSchema.migration(version) method. A migration must have an up block with the changes you want to apply to the schema, and a down block reversing the change made by up.

Use execute inside up and down to run the queries that will modify the schema.

Here is an example of a migration file:

require "cassandra-schema"

CassandraSchema.migration(1) do
  up do
    execute <<~CQL
      CREATE TABLE table_by_name (
        id uuid,
        name text,
        description text,
        PRIMARY KEY (id, name)
      ) WITH CLUSTERING ORDER BY (name ASC)
    CQL

    execute <<~CQL
      CREATE MATERIALIZED VIEW table_by_description AS
        SELECT
          id,
          name,
          description
        FROM table_by_name
        WHERE id IS NOT NULL
          AND name IS NOT NULL
          AND description IS NOT NULL
        PRIMARY KEY (id, description, name)
        WITH CLUSTERING ORDER BY (description ASC, name ASC)
    CQL
  end

  down do
    execute "DROP MATERIALIZED VIEW table_by_description"
    execute "DROP TABLE table_by_name"
  end
end

Once you defined your migrations, you can use CassandraSchema::Migrator to run them.

require "cassandra-schema/migrator"

migrator = CassandraSchema::Migrator.new(
  connection: CONN, # any connection object implementing `execute` method
  migrations: CassandraSchema.migrations, # list of migrations
  logger: Logger.new, # any logger object implementing `info` and `error` methods
  options: {}, # additional configuration
)

Migrate to lastest version:

migrator.migrate

Migrate to certain version:

migrator.migrate(2)

CassandraSchema tracks which migrations you have already run.

You can install it using rubygems.

gem install cassandra-schema

If you find a bug or want to collaborate with the code, you can:

• Report issues trhough the issue tracker
• Fork the repository into your own account and submit a Pull Request

These people have donated time to reviewing and improving this gem:

• Ary Borenszweig
• Joe Eli McIlvain
• Lucas Tolchinsky
• Matías Flores

MIT License

Copyright (c) 2017 Lautaro Orazi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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