diff options
Diffstat (limited to 'activerecord/lib/active_record/relation/calculations.rb')
| -rw-r--r-- | activerecord/lib/active_record/relation/calculations.rb | 53 |
1 files changed, 39 insertions, 14 deletions
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb index 42d43224fa..f215c95f51 100644 --- a/activerecord/lib/active_record/relation/calculations.rb +++ b/activerecord/lib/active_record/relation/calculations.rb @@ -130,8 +130,15 @@ module ActiveRecord # end def calculate(operation, column_name) if has_include?(column_name) - relation = construct_relation_for_association_calculations - relation.distinct! if operation.to_s.downcase == "count" + relation = apply_join_dependency + + if operation.to_s.downcase == "count" + relation.distinct! + # PostgreSQL: ORDER BY expressions must appear in SELECT list when using DISTINCT + if (column_name == :all || column_name.nil?) && select_values.empty? + relation.order_values = [] + end + end relation.calculate(operation, column_name) else @@ -180,8 +187,10 @@ module ActiveRecord end if has_include?(column_names.first) - construct_relation_for_association_calculations.pluck(*column_names) + relation = apply_join_dependency + relation.pluck(*column_names) else + enforce_raw_sql_whitelist(column_names) relation = spawn relation.select_values = column_names.map { |cn| @klass.has_attribute?(cn) || @klass.attribute_alias?(cn) ? arel_attribute(cn) : cn @@ -191,6 +200,24 @@ module ActiveRecord end end + # Pick the value(s) from the named column(s) in the current relation. + # This is short-hand for <tt>relation.limit(1).pluck(*column_names).first</tt>, and is primarily useful + # when you have a relation that's already narrowed down to a single row. + # + # Just like #pluck, #pick will only load the actual value, not the entire record object, so it's also + # more efficient. The value is, again like with pluck, typecast by the column type. + # + # Person.where(id: 1).pick(:name) + # # SELECT people.name FROM people WHERE id = 1 LIMIT 1 + # # => 'David' + # + # Person.where(id: 1).pick(:name, :email_address) + # # SELECT people.name, people.email_address FROM people WHERE id = 1 LIMIT 1 + # # => [ 'David', 'david@loudthinking.com' ] + def pick(*column_names) + limit(1).pluck(*column_names).first + end + # Pluck all the ID's for the relation using the table's primary key # # Person.ids # SELECT people.id FROM people @@ -215,7 +242,7 @@ module ActiveRecord if operation == "count" column_name ||= select_for_count if column_name == :all - if distinct && !(has_limit_or_offset? && order_values.any?) + if distinct && (group_values.any? || select_values.empty? && order_values.empty?) column_name = primary_key end elsif column_name =~ /\s*DISTINCT[\s(]+/i @@ -233,7 +260,7 @@ module ActiveRecord def aggregate_column(column_name) return column_name if Arel::Expressions === column_name - if @klass.has_attribute?(column_name.to_s) || @klass.attribute_alias?(column_name.to_s) + if @klass.has_attribute?(column_name) || @klass.attribute_alias?(column_name) @klass.arel_attribute(column_name) else Arel.sql(column_name == :all ? "*" : column_name.to_s) @@ -247,7 +274,7 @@ module ActiveRecord def execute_simple_calculation(operation, column_name, distinct) #:nodoc: column_alias = column_name - if operation == "count" && has_limit_or_offset? + if operation == "count" && (column_name == :all && distinct || has_limit_or_offset?) # Shortcut when limit is zero. return 0 if limit_value == 0 @@ -389,14 +416,12 @@ module ActiveRecord end def build_count_subquery(relation, column_name, distinct) - relation.select_values = [ - if column_name == :all - distinct ? table[Arel.star] : Arel.sql("1") - else - column_alias = Arel.sql("count_column") - aggregate_column(column_name).as(column_alias) - end - ] + if column_name == :all + relation.select_values = [ Arel.sql(FinderMethods::ONE_AS_ONE) ] unless distinct + else + column_alias = Arel.sql("count_column") + relation.select_values = [ aggregate_column(column_name).as(column_alias) ] + end subquery = relation.arel.as(Arel.sql("subquery_for_count")) select_value = operation_over_aggregate_column(column_alias || Arel.star, "count", false) |