method

columns_for_distinct

v5.2.3 - Show latest stable - 0 notes - Class: ActiveRecord::ConnectionAdapters

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What's this?

columns_for_distinct(columns, orders) public

In MySQL 5.7.5 and up, ONLY_FULL_GROUP_BY affects handling of queries that use DISTINCT and ORDER BY. It requires the ORDER BY columns in the select list for distinct queries, and requires that the ORDER BY include the distinct column. See dev.mysql.com/doc/refman/5.7/en/group-by-handling.html

Show source

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 510
      def columns_for_distinct(columns, orders) # :nodoc:
        order_columns = orders.reject(&:blank?).map { |s|
          # Convert Arel node to string
          s = s.to_sql unless s.is_a?(String)
          # Remove any ASC/DESC modifiers
          s.gsub(/\s+(?:ASC|DESC)\b/, "")
        }.reject(&:blank?).map.with_index { |column, i| "#{column} AS alias_#{i}" }

        (order_columns << super).join(", ")
      end

columns_for_distinct

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