PERF: Active Record #pluck is twice faster

PERF: SqlBuilder bypasses AR converters and uses PG directly

lib/freedom_patches/fast_pluck.rb

@@ -0,0 +1,108 @@
+# Speeds up #pluck so its about 2.2x faster, importantly makes pluck avoid creation of a slew
+# of AR objects
+
+require_dependency 'sql_builder'
+
+class ActiveRecord::Relation
+
+  # class RailsDateTimeDecoder < PG::SimpleDecoder
+  #   def decode(string, tuple=nil, field=nil)
+  #     if Rails.version >= "4.2.0"
+  #       @caster ||= ActiveRecord::Type::DateTime.new
+  #       @caster.type_cast_from_database(string)
+  #     else
+  #       ActiveRecord::ConnectionAdapters::Column.string_to_time string
+  #     end
+  #   end
+  # end
+  #
+  # class ActiveRecordTypeMap < PG::BasicTypeMapForResults
+  #   def initialize(connection)
+  #     super(connection)
+  #     rm_coder 0, 1114
+  #     add_coder RailsDateTimeDecoder.new(name: "timestamp", oid: 1114, format: 0)
+  #     # we don't need deprecations
+  #     self.default_type_map = PG::TypeMapInRuby.new
+  #   end
+  # end
+  #
+  # def self.pg_type_map
+  #   conn = ActiveRecord::Base.connection.raw_connection
+  #   @typemap ||= ActiveRecordTypeMap.new(conn)
+  # end
+
+  class ::ActiveRecord::ConnectionAdapters::PostgreSQLAdapter
+    if Rails.version >= "4.2.0"
+      def select_raw(arel, name = nil, binds = [], &block)
+        arel, binds = binds_from_relation arel, binds
+        sql = to_sql(arel, binds)
+        execute_and_clear(sql, name, binds, &block)
+      end
+    else
+
+      def select_raw(arel, name = nil, binds = [], &block)
+        arel, binds = binds_from_relation arel, binds
+        sql = to_sql(arel, binds)
+
+        result = without_prepared_statement?(binds) ? exec_no_cache(sql, 'SQL', binds) :
+                                                        exec_cache(sql, 'SQL', binds)
+        yield result, nil
+      end
+    end
+  end
+
+  def pluck(*cols)
+
+    conn = ActiveRecord::Base.connection
+    relation = self
+
+    cols.map! do |column_name|
+      if column_name.is_a?(Symbol) && attribute_alias?(column_name)
+        attribute_alias(column_name)
+      else
+        column_name.to_s
+      end
+    end
+
+
+    if has_include?(cols.first)
+      construct_relation_for_association_calculations.pluck(*cols)
+    else
+      relation = spawn
+
+      relation.select_values = cols.map { |cn|
+        columns_hash.key?(cn) ? arel_table[cn] : cn
+      }
+
+      conn.select_raw(relation) do |result,_|
+        result.type_map = SqlBuilder.pg_type_map
+        result.nfields == 1 ? result.column_values(0) : result.values
+      end
+
+    end
+  end
+end
+
+# require 'benchmark/ips'
+#
+# ENV['RAILS_ENV'] = 'production'
+# require File.expand_path("../../config/environment", __FILE__)
+#
+# Benchmark.ips do |x|
+#   x.report("fast_pluck") do
+#     Post.where(topic_id: 48464).fast_pluck(:id)
+#   end
+#
+#   x.report("pluck") do
+#     Post.where(topic_id: 48464).pluck(:id)
+#   end
+# end
+#
+# % ruby tmp/fast_pluck.rb
+# Calculating -------------------------------------
+#           fast_pluck   165.000  i/100ms
+#                pluck    80.000  i/100ms
+# -------------------------------------------------
+#           fast_pluck      1.720k (± 8.8%) i/s -      8.580k
+#                pluck    807.913  (± 4.0%) i/s -      4.080k
+#

lib/sql_builder.rb

@@ -36,9 +36,9 @@ class SqlBuilder
       when :where, :where2
         joined = "WHERE " << v.map{|c| "(" << c << ")" }.join(" AND ")
       when :join
-        joined = v.map{|v| "JOIN " << v }.join("\n")
+        joined = v.map{|item| "JOIN " << item }.join("\n")
       when :left_join
-        joined = v.map{|v| "LEFT JOIN " << v }.join("\n")
+        joined = v.map{|item| "LEFT JOIN " << item }.join("\n")
       when :limit
         joined = "LIMIT " << v.last.to_s
       when :offset
@@ -69,46 +69,50 @@ class SqlBuilder
     end
   end
 
-  #AS reloads this on tests
-  remove_const :FTYPE_MAP if defined? FTYPE_MAP
-
-  if Rails.version >= "4.2.0"
-    FTYPE_MAP = {
-      23 => ActiveRecord::Type::Integer.new,
-      1114 => ActiveRecord::Type::DateTime.new,
-      16 => ActiveRecord::Type::Boolean.new
-    }
-  else
-    FTYPE_MAP = {
-      23 => :value_to_integer,
-      1114 => :string_to_time,
-      16 => :value_to_boolean
-    }
-  end
-
   def self.map_exec(klass, sql, args = {})
     self.new(sql).map_exec(klass, args)
   end
 
+  class RailsDateTimeDecoder < PG::SimpleDecoder
+    def decode(string, tuple=nil, field=nil)
+      if Rails.version >= "4.2.0"
+        @caster ||= ActiveRecord::Type::DateTime.new
+        @caster.type_cast_from_database(string)
+      else
+        ActiveRecord::ConnectionAdapters::Column.string_to_time string
+      end
+    end
+  end
+
+
+  class ActiveRecordTypeMap < PG::BasicTypeMapForResults
+    def initialize(connection)
+      super(connection)
+      rm_coder 0, 1114
+      add_coder RailsDateTimeDecoder.new(name: "timestamp", oid: 1114, format: 0)
+      # we don't need deprecations
+     	self.default_type_map = PG::TypeMapInRuby.new
+    end
+  end
+
+  def self.pg_type_map
+    conn = ActiveRecord::Base.connection.raw_connection
+    @typemap ||= ActiveRecordTypeMap.new(conn)
+  end
+
   def map_exec(klass = OpenStruct, args = {})
     results = exec(args)
+    results.type_map = SqlBuilder.pg_type_map
 
     setters = results.fields.each_with_index.map do |f, index|
-      [(f.dup << "=").to_sym, FTYPE_MAP[results.ftype(index)]]
+      f.dup << "="
     end
+
     values = results.values
     values.map! do |row|
       mapped = klass.new
-      setters.each_with_index do |mapper, index|
-        translated = row[index]
-        if mapper[1] && !translated.nil?
-          if Rails.version >= "4.2.0"
-            translated = mapper[1].type_cast_from_database(translated)
-          else
-            translated = ActiveRecord::ConnectionAdapters::Column.send mapper[1], translated
-          end
-        end
-        mapped.send mapper[0], translated
+      setters.each_with_index do |name, index|
+        mapped.send name, row[index]
       end
       mapped
     end

lib/topic_query.rb

@@ -137,7 +137,6 @@ class TopicQuery
     pinned_ids = query.where('pinned_at IS NOT NULL AND category_id = ?', category.id)
                       .order('pinned_at DESC').pluck(:id)
     non_pinned_ids = query.where('pinned_at IS NULL OR category_id <> ?', category.id).pluck(:id)
-
     (pinned_ids + non_pinned_ids)[0...@options[:per_page]]
   end
 

spec/models/post_action_spec.rb

@@ -2,9 +2,6 @@ require 'spec_helper'
 require_dependency 'post_destroyer'
 
 describe PostAction do
-  it { is_expected.to belong_to :user }
-  it { is_expected.to belong_to :post }
-  it { is_expected.to belong_to :post_action_type }
   it { is_expected.to rate_limit }
 
   let(:moderator) { Fabricate(:moderator) }
@@ -458,6 +455,7 @@ describe PostAction do
       end
 
       expect(topic.reload.closed).to eq(true)
+
     end
 
   end