vendor/gems/composite_primary_keys-1.1.0/lib/composite_primary_keys/calculations.rb

   1 module CompositePrimaryKeys
   2   module ActiveRecord
   3     module Calculations
   4       def self.append_features(base)
   5         super
   6         base.send(:extend, ClassMethods)
   7       end
   8
   9       module ClassMethods
  10         def construct_calculation_sql(operation, column_name, options) #:nodoc:
  11           operation = operation.to_s.downcase
  12           options = options.symbolize_keys
  13
  14           scope           = scope(:find)
  15           merged_includes = merge_includes(scope ? scope[:include] : [], options[:include])
  16           aggregate_alias = column_alias_for(operation, column_name)
  17           use_workaround  = !connection.supports_count_distinct? && options[:distinct] && operation.to_s.downcase == 'count'
  18           join_dependency = nil
  19
  20           if merged_includes.any? && operation.to_s.downcase == 'count'
  21             options[:distinct] = true
  22             use_workaround  = !connection.supports_count_distinct?
  23             column_name = options[:select] || primary_key.map{ |part| "#{quoted_table_name}.#{connection.quote_column_name(part)}"}.join(',')
  24           end
  25
  26           sql  = "SELECT #{operation}(#{'DISTINCT ' if options[:distinct]}#{column_name}) AS #{aggregate_alias}"
  27
  28           # A (slower) workaround if we're using a backend, like sqlite, that doesn't support COUNT DISTINCT.
  29           sql = "SELECT COUNT(*) AS #{aggregate_alias}" if use_workaround
  30
  31           sql << ", #{connection.quote_column_name(options[:group_field])} AS #{options[:group_alias]}" if options[:group]
  32           sql << " FROM (SELECT DISTINCT #{column_name}" if use_workaround
  33           sql << " FROM #{quoted_table_name} "
  34           if merged_includes.any?
  35             join_dependency = ::ActiveRecord::Associations::ClassMethods::JoinDependency.new(self, merged_includes, options[:joins])
  36             sql << join_dependency.join_associations.collect{|join| join.association_join }.join
  37           end
  38           add_joins!(sql, options, scope)
  39           add_conditions!(sql, options[:conditions], scope)
  40           add_limited_ids_condition!(sql, options, join_dependency) if \
  41             join_dependency &&
  42             !using_limitable_reflections?(join_dependency.reflections) &&
  43             ((scope && scope[:limit]) || options[:limit])
  44
  45           if options[:group]
  46             group_key = connection.adapter_name == 'FrontBase' ?  :group_alias : :group_field
  47             sql << " GROUP BY #{connection.quote_column_name(options[group_key])} "
  48           end
  49
  50           if options[:group] && options[:having]
  51             # FrontBase requires identifiers in the HAVING clause and chokes on function calls
  52             if connection.adapter_name == 'FrontBase'
  53               options[:having].downcase!
  54               options[:having].gsub!(/#{operation}\s*\(\s*#{column_name}\s*\)/, aggregate_alias)
  55             end
  56
  57             sql << " HAVING #{options[:having]} "
  58           end
  59
  60           sql << " ORDER BY #{options[:order]} " if options[:order]
  61           add_limit!(sql, options, scope)
  62           sql << ') w1' if use_workaround # assign a dummy table name as required for postgresql
  63           sql
  64         end
  65       end
  66     end
  67   end
  68 end