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# speed up pluck
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 fast_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.fast_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 = ActiveRecord::Relation.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
#
@pabloh
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pabloh commented Apr 2, 2016

@SamSaffron, what about mysql support?, is it tested?.

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