diff options
Diffstat (limited to 'lib/arel/algebra/relations/operations/project.rb')
-rw-r--r-- | lib/arel/algebra/relations/operations/project.rb | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/lib/arel/algebra/relations/operations/project.rb b/lib/arel/algebra/relations/operations/project.rb new file mode 100644 index 0000000000..223d320e22 --- /dev/null +++ b/lib/arel/algebra/relations/operations/project.rb @@ -0,0 +1,20 @@ +module Arel + class Project < Compound + attributes :relation, :projections + deriving :== + + def initialize(relation, *projections, &block) + @relation = relation + @projections = (projections + arguments_from_block(relation, &block)) \ + .collect { |p| p.bind(relation) } + end + + def attributes + @attributes ||= projections.collect { |p| p.bind(self) } + end + + def externalizable? + attributes.any?(&:aggregation?) or relation.externalizable? + end + end +end |