1 files changed, 114 insertions, 0 deletions
diff --git a/lib/gitlab/sherlock/query.rb b/lib/gitlab/sherlock/query.rb
new file mode 100644
index 00000000000..4917c4ae2ac
--- /dev/null
+++ b/lib/gitlab/sherlock/query.rb
@@ -0,0 +1,114 @@
+module Gitlab
+  module Sherlock
+    class Query
+      attr_reader :id, :query, :started_at, :finished_at, :backtrace
+
+      # SQL identifiers that should be prefixed with newlines.
+      PREFIX_NEWLINE = /
+        \s+(FROM
+          |(LEFT|RIGHT)?INNER\s+JOIN
+          |(LEFT|RIGHT)?OUTER\s+JOIN
+          |WHERE
+          |AND
+          |GROUP\s+BY
+          |ORDER\s+BY
+          |LIMIT
+          |OFFSET)\s+/ix # Vim indent breaks when this is on a newline :<
+
+      # Creates a new Query using a String and a separate Array of bindings.
+      #
+      # query - A String containing a SQL query, optionally with numeric
+      #         placeholders (`$1`, `$2`, etc).
+      #
+      # bindings - An Array of ActiveRecord columns and their values.
+      # started_at - The start time of the query as a Time-like object.
+      # finished_at - The completion time of the query as a Time-like object.
+      #
+      # Returns a new Query object.
+      def self.new_with_bindings(query, bindings, started_at, finished_at)
+        bindings.each_with_index do |(_, value), index|
+          quoted_value = ActiveRecord::Base.connection.quote(value)
+
+          query = query.gsub("$#{index + 1}", quoted_value)
+        end
+
+        new(query, started_at, finished_at)
+      end
+
+      # query - The SQL query as a String (without placeholders).
+      # started_at - The start time of the query as a Time-like object.
+      # finished_at - The completion time of the query as a Time-like object.
+      def initialize(query, started_at, finished_at)
+        @id = SecureRandom.uuid
+        @query = query
+        @started_at = started_at
+        @finished_at = finished_at
+        @backtrace = caller_locations.map do |loc|
+          Location.from_ruby_location(loc)
+        end
+
+        unless @query.end_with?(';')
+          @query += ';'
+        end
+      end
+
+      # Returns the query duration in milliseconds.
+      def duration
+        @duration ||= (@finished_at - @started_at) * 1000.0
+      end
+
+      def to_param
+        @id
+      end
+
+      # Returns a human readable version of the query.
+      def formatted_query
+        @formatted_query ||= format_sql(@query)
+      end
+
+      # Returns the last application frame of the backtrace.
+      def last_application_frame
+        @last_application_frame ||= @backtrace.find(&:application?)
+      end
+
+      # Returns an Array of application frames (excluding Gems and the likes).
+      def application_backtrace
+        @application_backtrace ||= @backtrace.select(&:application?)
+      end
+
+      # Returns the query plan as a String.
+      def explain
+        unless @explain
+          ActiveRecord::Base.connection.transaction do
+            @explain = raw_explain(@query).values.flatten.join("\n")
+
+            # Roll back any queries that mutate data so we don't mess up
+            # anything when running explain on an INSERT, UPDATE, DELETE, etc.
+            raise ActiveRecord::Rollback
+          end
+        end
+
+        @explain
+      end
+
+      private
+
+      def raw_explain(query)
+        if Gitlab::Database.postgresql?
+          explain = "EXPLAIN ANALYZE #{query};"
+        else
+          explain = "EXPLAIN #{query};"
+        end
+
+        ActiveRecord::Base.connection.execute(explain)
+      end
+
+      def format_sql(query)
+        query.each_line.
+          map { |line| line.strip }.
+          join("\n").
+          gsub(PREFIX_NEWLINE) { "\n#{$1} " }
+      end
+    end
+  end
+end