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:
-
application
-
pid
-
socket
-
db_host
-
database
-
source_location
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.
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
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
Source
# 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
Returns an SQL comment String
containing the query log tags. Sets and returns a cached comment if cache_query_log_tags
is true
.
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
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
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
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