module ActiveRecord::QueryLogs

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:

Action Controller adds default tags when loaded:

Active Job adds default tags when loaded:

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.

Example:

config.active_record.query_log_tags = [
  :namespaced_controller,
  :action,
  :job,
  {
    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

Private Class Methods

build_handler(name, handler = nil) click to toggle source
# File lib/active_record/query_logs.rb, line 180
def build_handler(name, handler = nil)
  handler ||= @taggings[name]
  if handler.nil?
    GetKeyHandler.new(name)
  elsif handler.respond_to?(:call)
    if handler.arity == 0
      ZeroArityHandler.new(handler)
    else
      handler
    end
  else
    IdentityHandler.new(handler)
  end
end
comment(connection) click to toggle source

Returns an SQL comment String containing the query log tags. Sets and returns a cached comment if cache_query_log_tags is true.

# File lib/active_record/query_logs.rb, line 197
def comment(connection)
  if cache_query_log_tags
    self.cached_comment ||= uncached_comment(connection)
  else
    uncached_comment(connection)
  end
end
escape_sql_comment(content) click to toggle source
# File lib/active_record/query_logs.rb, line 213
def escape_sql_comment(content)
  # Sanitize a string to appear within a SQL comment
  # For compatibility, this also surrounding "/*+", "/*", and "*/"
  # characters, possibly with single surrounding space.
  # Then follows that by replacing any internal "*/" or "/ *" with
  # "* /" or "/ *"
  comment = content.to_s.dup
  comment.gsub!(%r{\A\s*/\*\+?\s?|\s?\*/\s*\Z}, "")
  comment.gsub!("*/", "* /")
  comment.gsub!("/*", "/ *")
  comment
end
rebuild_handlers() click to toggle source
# File lib/active_record/query_logs.rb, line 166
def rebuild_handlers
  handlers = []
  @tags.each do |i|
    if i.is_a?(Hash)
      i.each do |k, v|
        handlers << [k, build_handler(k, v)]
      end
    else
      handlers << [i, build_handler(i)]
    end
  end
  handlers.sort_by! { |(key, _)| key.to_s }
end
tag_content(connection) click to toggle source
# File lib/active_record/query_logs.rb, line 226
def tag_content(connection)
  context = ActiveSupport::ExecutionContext.to_h
  context[:connection] ||= connection

  pairs = @handlers.filter_map do |(key, handler)|
    val = handler.call(context)
    @formatter.format(key, val) unless val.nil?
  end
  @formatter.join(pairs)
end
uncached_comment(connection) click to toggle source
# File lib/active_record/query_logs.rb, line 205
def uncached_comment(connection)
  content = tag_content(connection)

  if content.present?
    "/*#{escape_sql_comment(content)}*/"
  end
end