method

subquery_for

Ruby on Rails latest stable (v7.1.3.2) - 0 notes - Class: AbstractMysqlAdapter

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What's this?

Method deprecated or moved

This method is deprecated or moved on the latest stable version. The last existing version (v4.2.9) is shown here.

subquery_for(key, select) protected

MySQL is too stupid to create a temporary table for use subquery, so we have to give it some prompting in the form of a subsubquery. Ugh!

Show source

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 735
      def subquery_for(key, select)
        subsubselect = select.clone
        subsubselect.projections = [key]

        # Materialize subquery by adding distinct
        # to work with MySQL 5.7.6 which sets optimizer_switch='derived_merge=on'
        subsubselect.distinct unless select.limit || select.offset || select.orders.any?

        subselect = Arel::SelectManager.new(select.engine)
        subselect.project Arel.sql(key.name)
        subselect.from subsubselect.as('__active_record_temp')
      end

subquery_for

Related methods

Method deprecated or moved