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Active Record Query Logs

Automatically append comments to SQL queries with runtime information tags. This can be used to trace troublesome SQL statements back to the application code that generated these statements.

Query logs can be enabled via Rails configuration in config/application.rb or an initializer:

config.active_record.query_log_tags_enabled = true

By default the name of the application, the name and action of the controller, or the name of the job are logged. The default format is SQLCommenter. The tags shown in a query comment can be configured via Rails configuration:

config.active_record.query_log_tags = [ :application, :controller, :action, :job ]

Active Record defines default tags available for use:

  • application

  • pid

  • socket

  • db_host

  • database

Action Controller adds default tags when loaded:

  • controller

  • action

  • namespaced_controller

Active Job adds default tags when loaded:

  • job

New comment tags can be defined by adding them in a Hash to the tags Array. Tags can have dynamic content by setting a Proc or lambda value in the Hash, and can reference any value stored by Rails in the context object. ActiveSupport::CurrentAttributes can be used to store application values. Tags with nil values are omitted from the query comment.

Escaping is performed on the string returned, however untrusted user input should not be used.


config.active_record.query_log_tags = [
    request_id: ->(context) { context[:controller]&.request&.request_id },
    job_id: ->(context) { context[:job]&.job_id },
    tenant_id: -> { Current.tenant&.id },
    static: "value",

By default the name of the application, the name and action of the controller, or the name of the job are logged using the SQLCommenter format. This can be changed via config.active_record.query_log_tags_format

Tag comments can be prepended to the query:

ActiveRecord::QueryLogs.prepend_comment = true

For applications where the content will not change during the lifetime of the request or job execution, the tags can be cached for reuse in every query:

config.active_record.cache_query_log_tags = true

Class Public methods


Updates the formatter to be what the passed in format is.

# File activerecord/lib/active_record/query_logs.rb, line 99
def update_formatter(format)
  self.tags_formatter =
    case format
    when :legacy
    when :sqlcommenter
      raise ArgumentError, "Formatter is unsupported: #{formatter}"