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 = 
[
  "pending",     # The migration has been created 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.
  "delayed",     # The migration was created, but waiting approval from the user to start running.
]
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 pending, or running.

Returns:

  • (Boolean) —

    whether the migration is active.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 67

def active?
  pending? || running?
end

#attempts_exceeded? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 143

def attempts_exceeded?
  attempts >= max_attempts
end

#cancel ⇒ Boolean

Cancel this schema migration. No-op if migration is completed.

Returns:

  • (Boolean) —

    whether this schema migration was cancelled.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 129

def cancel
  if completed?
    false
  elsif pending? || errored? || delayed? || stuck?
    cancelled!
    true
  end
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 58

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

#enqueue ⇒ Boolean

Enqueue this data migration. No-op if migration is not delayed.

Returns:

  • (Boolean) —

    whether this data migration was enqueued.



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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 116

def enqueue
  if delayed?
    pending!
    true
  else
    false
  end
end

#index_addition? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/online_migrations/background_schema_migrations/migration.rb', line 138

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 94

def retry
  if failed?
    update!(
      status: :pending,
      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 148

def run
  on_shard_if_present do
    with_connection do |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
end

#stuck? ⇒ Boolean

Whether the migration is considered stuck.

Returns:

  • (Boolean) 


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

def stuck?
  index_addition? && running? && !index_build_in_progress?
end