method

distinct

v3.1.0 - Show latest stable - Class: ActiveRecord::ConnectionAdapters::PostgreSQLAdapter

distinct(columns, orders)

public

Returns a SELECT DISTINCT clause for a given set of columns and a given ORDER BY clause.

PostgreSQL requires the ORDER BY columns in the select list for distinct queries, and requires that the ORDER BY include the distinct column.

distinct("posts.id", "posts.created_at desc")

# File activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb, line 931
      def distinct(columns, orders) #:nodoc:
        return "DISTINCT #{columns}" if orders.empty?

        # Construct a clean list of column names from the ORDER BY clause, removing
        # any ASC/DESC modifiers
        order_columns = orders.collect { |s| s.gsub(/\s+(ASC|DESC)\s*/, '') }
        order_columns.delete_if { |c| c.blank? }
        order_columns = order_columns.zip((0...order_columns.size).to_a).map { |s,i| "#{s} AS alias_#{i}" }

        "DISTINCT #{columns}, #{order_columns * ', '}"
      end

distinct

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