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Diffstat (limited to 'activerecord/lib/active_record/explain.rb')
-rw-r--r-- | activerecord/lib/active_record/explain.rb | 82 |
1 files changed, 82 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb new file mode 100644 index 0000000000..313fdb3487 --- /dev/null +++ b/activerecord/lib/active_record/explain.rb @@ -0,0 +1,82 @@ +require 'active_support/core_ext/class/attribute' + +module ActiveRecord + module Explain + def self.extended(base) + # If a query takes longer than these many seconds we log its query plan + # automatically. nil disables this feature. + base.config_attribute :auto_explain_threshold_in_seconds, :global => true + end + + # If auto explain is enabled, this method triggers EXPLAIN logging for the + # queries triggered by the block if it takes more than the threshold as a + # whole. That is, the threshold is not checked against each individual + # query, but against the duration of the entire block. This approach is + # convenient for relations. + # + # The available_queries_for_explain thread variable collects the queries + # to be explained. If the value is nil, it means queries are not being + # currently collected. A false value indicates collecting is turned + # off. Otherwise it is an array of queries. + def logging_query_plan # :nodoc: + return yield unless logger + + threshold = auto_explain_threshold_in_seconds + current = Thread.current + if threshold && current[:available_queries_for_explain].nil? + begin + queries = current[:available_queries_for_explain] = [] + start = Time.now + result = yield + logger.warn(exec_explain(queries)) if Time.now - start > threshold + result + ensure + current[:available_queries_for_explain] = nil + end + else + yield + end + end + + # Relation#explain needs to be able to collect the queries regardless of + # whether auto explain is enabled. This method serves that purpose. + def collecting_queries_for_explain # :nodoc: + current = Thread.current + original, current[:available_queries_for_explain] = current[:available_queries_for_explain], [] + return yield, current[:available_queries_for_explain] + ensure + # Note that the return value above does not depend on this assigment. + current[:available_queries_for_explain] = original + end + + # Makes the adapter execute EXPLAIN for the tuples of queries and bindings. + # Returns a formatted string ready to be logged. + def exec_explain(queries) # :nodoc: + queries && queries.map do |sql, bind| + [].tap do |msg| + msg << "EXPLAIN for: #{sql}" + unless bind.empty? + bind_msg = bind.map {|col, val| [col.name, val]}.inspect + msg.last << " #{bind_msg}" + end + msg << connection.explain(sql, bind) + end.join("\n") + end.join("\n") + end + + # Silences automatic EXPLAIN logging for the duration of the block. + # + # This has high priority, no EXPLAINs will be run even if downwards + # the threshold is set to 0. + # + # As the name of the method suggests this only applies to automatic + # EXPLAINs, manual calls to <tt>ActiveRecord::Relation#explain</tt> run. + def silence_auto_explain + current = Thread.current + original, current[:available_queries_for_explain] = current[:available_queries_for_explain], false + yield + ensure + current[:available_queries_for_explain] = original + end + end +end |