Class: OnlineMigrations::BackgroundSchemaMigrations::Migration

Inherits:
ApplicationRecord
  • Object
show all
Includes:
ShardAware
Defined in:
lib/online_migrations/background_schema_migrations/migration.rb

Overview

Note:

The records of this class should not be created manually, but via ‘enqueue_background_schema_migration` helper inside migrations.

Class representing background schema migration.

Constant Summary collapse

STATUSES = 
[
  "enqueued",    # The migration has been enqueued by the user.
  "running",     # The migration is being performed by a migration executor.
  "errored",     # The migration raised an error during last run.
  "failed",      # The migration raises an error when running and retry attempts exceeded.
  "succeeded",   # The migration finished without error.
  "cancelled",   # The migration was cancelled by the user.
]
MAX_IDENTIFIER_LENGTH = 
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Instance Method Summary collapse

Methods included from ShardAware

#connection_class, #connection_class_name=, #on_shard_if_present

Instance Method Details

#active? ⇒ Boolean

Returns whether the migration is active, which is defined as having a status of enqueued, or running.

Returns:

  • (Boolean) —

    whether the migration is active.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 65

def active?
  enqueued? || running?
end

#attempts_exceeded? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 122

def attempts_exceeded?
  attempts >= max_attempts
end

#completed? ⇒ Boolean

Returns whether the migration is completed, which is defined as having a status of succeeded, failed, or cancelled.

Returns:

  • (Boolean) —

    whether the migration is completed.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 56

def completed?
  succeeded? || failed? || cancelled?
end

#index_addition? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 117

def index_addition?
  definition.match?(/create (unique )?index/i)
end

#pausable? ⇒ Boolean

Returns whether this migration is pausable.

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 73

def pausable?
  false
end

#progress ⇒ nil

Dummy method to support the same interface as background data migrations.

Returns:

  • (nil) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 81

def progress
end

#retry ⇒ Object

Mark this migration as ready to be processed again.

This is used to manually retrying failed migrations.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 99

def retry
  if failed?
    update!(
      status: :enqueued,
      attempts: 0,
      started_at: nil,
      finished_at: nil,
      error_class: nil,
      error_message: nil,
      backtrace: nil
    )

    true
  else
    false
  end
end

#run ⇒ Object 



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 127

def run
  on_shard_if_present do
    connection = connection_class.connection

    connection.with_lock_retries do
      statement_timeout = self.statement_timeout || OnlineMigrations.config.statement_timeout

      with_statement_timeout(connection, statement_timeout) do
        if index_addition?
          index = connection.indexes(table_name).find { |i| name.match?(/\b#{i.name}\b/) }
          if index
            if index.valid?
              return
            else
              connection.remove_index(table_name, name: index.name, algorithm: :concurrently)
            end
          end
        end

        connection.execute(definition)

        # Outdated statistics + a new index can hurt performance of existing queries.
        if OnlineMigrations.config.auto_analyze
          connection.execute("ANALYZE #{table_name}")
        end
      end
    end
  end
end

#stuck? ⇒ Boolean

Whether the migration is considered stuck (is running for some configured time).

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 86

def stuck?
  if index_addition?
    running? && !index_build_in_progress?
  else
    stuck_timeout = (statement_timeout || 1.day) + 10.minutes
    running? && updated_at <= stuck_timeout.seconds.ago
  end
end