method

subquery_for

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

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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 (v5.2.3) is shown here.

subquery_for(key, select) private

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 723
        def subquery_for(key, select)
          subselect = select.clone
          subselect.projections = [key]

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

          key_name = quote_column_name(key.name)
          Arel::SelectManager.new(subselect.as("__active_record_temp")).project(Arel.sql(key_name))
        end

subquery_for

Related methods

Method deprecated or moved