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module Arel
class Relation
def session
Session.new
end
def to_sql(formatter = Sql::SelectStatement.new(self))
formatter.select [
"SELECT #{attributes.collect { |a| a.to_sql(Sql::SelectClause.new(self)) }.join(', ')}",
"FROM #{table_sql(Sql::TableReference.new(self))}",
(joins(self) unless joins(self).blank? ),
("WHERE #{selects.collect { |s| s.to_sql(Sql::WhereClause.new(self)) }.join("\n\tAND ")}" unless selects.blank? ),
("ORDER BY #{orders.collect { |o| o.to_sql(Sql::OrderClause.new(self)) }.join(', ')}" unless orders.blank? ),
("GROUP BY #{groupings.collect { |g| g.to_sql(Sql::GroupClause.new(self)) }.join(', ')}" unless groupings.blank? ),
("LIMIT #{taken}" unless taken.blank? ),
("OFFSET #{skipped}" unless skipped.blank? )
].compact.join("\n"), name
end
alias_method :to_s, :to_sql
def inclusion_predicate_sql
"IN"
end
def call(connection = engine.connection)
results = connection.execute(to_sql)
rows = []
results.each do |row|
rows << attributes.zip(row).to_hash
end
rows
end
def bind(relation)
self
end
def christener
@christener ||= Sql::Christener.new
end
def aggregation?
false
end
module Enumerable
include ::Enumerable
def each(&block)
session.read(self).each(&block)
end
def first
session.read(self).first
end
end
include Enumerable
module Operable
def join(other = nil, join_type = "INNER JOIN")
case other
when String
Join.new(other, self)
when Relation
JoinOperation.new(join_type, self, other)
else
self
end
end
def outer_join(other = nil)
join(other, "LEFT OUTER JOIN")
end
def select(*predicates)
predicates.all?(&:blank?) ? self : Selection.new(self, *predicates)
end
def project(*attributes)
attributes.all?(&:blank?) ? self : Projection.new(self, *attributes)
end
def alias
Alias.new(self)
end
def order(*attributes)
attributes.all?(&:blank?) ? self : Order.new(self, *attributes)
end
def take(taken = nil)
taken.blank?? self : Take.new(self, taken)
end
def skip(skipped = nil)
skipped.blank?? self : Skip.new(self, skipped)
end
def group(*groupings)
groupings.all?(&:blank?) ? self : Grouping.new(self, *groupings)
end
module Writable
def insert(record)
session.create Insertion.new(self, record); self
end
def update(assignments)
session.update Update.new(self, assignments); self
end
def delete
session.delete Deletion.new(self); self
end
end
include Writable
JoinOperation = Struct.new(:join_sql, :relation1, :relation2) do
def on(*predicates)
Join.new(join_sql, relation1, relation2, *predicates)
end
end
end
include Operable
module AttributeAccessable
def [](index)
case index
when Symbol, String
attribute_for_name(index)
when Attribute, Expression
attribute_for_attribute(index)
when Array
index.collect { |i| self[i] }
end
end
def attribute_for_name(name)
attributes.detect { |a| a.alias_or_name.to_s == name.to_s }
end
def attribute_for_attribute(attribute)
attributes.select { |a| a =~ attribute }.max do |a1, a2|
(attribute / a1) <=> (attribute / a2)
end
end
end
include AttributeAccessable
module DefaultOperations
def attributes; [] end
def selects; [] end
def orders; [] end
def inserts; [] end
def groupings; [] end
def joins(formatter = nil); nil end
def taken; nil end
def skipped; nil end
end
include DefaultOperations
end
end
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