diff options
Diffstat (limited to 'activerecord/lib')
3 files changed, 24 insertions, 5 deletions
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb index e075ecaf3c..d52695d162 100755 --- a/activerecord/lib/active_record/associations.rb +++ b/activerecord/lib/active_record/associations.rb @@ -1192,13 +1192,18 @@ module ActiveRecord end def construct_finder_sql_for_association_limiting(options, join_dependency) - scope = scope(:find) + scope = scope(:find) + is_distinct = include_eager_conditions?(options) || include_eager_order?(options) sql = "SELECT " - sql << "DISTINCT #{table_name}." if include_eager_conditions?(options) || include_eager_order?(options) - sql << primary_key + if is_distinct + ordered_columns = options[:order].to_s.split(',').collect! { |s| s.split.first } + sql << connection.distinct("#{table_name}.#{primary_key}", ordered_columns) + else + sql << primary_key + end sql << " FROM #{table_name} " - if include_eager_conditions?(options) || include_eager_order?(options) + if is_distinct sql << join_dependency.join_associations.collect(&:association_join).join add_joins!(sql, options, scope) end diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb index 1ed761b126..a098c02829 100644 --- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb +++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb @@ -279,6 +279,11 @@ module ActiveRecord sql << " DEFAULT #{quote(options[:default], options[:column])}" unless options[:default].nil? sql << " NOT NULL" if options[:null] == false end + + # SELECT DISTINCT clause for a given set of columns. PostgreSQL overrides this for custom DISTINCT syntax. + def distinct(columns, *order_columns) + "DISTINCT #{columns}" + end end end end diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb index a2eaac549e..975768a758 100644 --- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb +++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb @@ -186,7 +186,6 @@ module ActiveRecord execute "ROLLBACK" end - # SCHEMA STATEMENTS ======================================== # Return the list of all tables in the schema search path. @@ -384,6 +383,16 @@ module ActiveRecord 'bigint' end end + + # PostgreSQL requires the ORDER BY columns in the select list for distinct queries. + # If you select distinct by a column though, you must pass that column in the order by clause too: + # + # distinct("posts.id", 'posts.id', 'posts.created_at') + def distinct(columns, *order_columns) + order_columns.delete_if &:blank? + sql = "DISTINCT ON (#{columns}) #{columns}" + sql << (order_columns.any? ? ", #{order_columns * ', '}" : '') + end private BYTEA_COLUMN_TYPE_OID = 17 |