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module Arel
class Relation
def session
Session.new
end
def to_sql(formatter = Sql::SelectStatement.new(self))
formatter.select select_sql, self
end
alias_method :to_s, :to_sql
def select_sql
[
"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 #{wheres .collect { |w| w.to_sql(Sql::WhereClause.new(self)) }.join("\n\tAND ")}" unless wheres.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")
end
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 root
self
end
def christener
@christener ||= Sql::Christener.new
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_relation = nil, join_type = "INNER JOIN")
case other_relation
when String
Join.new(other_relation, self)
when Relation
JoinOperation.new(join_type, self, other_relation)
else
self
end
end
def outer_join(other_relation = nil)
join(other_relation, "LEFT OUTER JOIN")
end
[:where, :project, :order, :take, :skip, :group].each do |operation_name|
operation = <<-OPERATION
def #{operation_name}(*arguments, &block)
arguments.all?(&:blank?) && !block_given?? self : #{operation_name.to_s.classify}.new(self, *arguments, &block)
end
OPERATION
class_eval operation, __FILE__, __LINE__
end
def alias
Alias.new(self)
end
module Writable
def insert(record)
session.create Insert.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
find_attribute_matching_name(index)
when Attribute, Expression
find_attribute_matching_attribute(index)
when Array
index.collect { |i| self[i] }
end
end
def find_attribute_matching_name(name)
attributes.detect { |a| a.named?(name) }
end
def find_attribute_matching_attribute(attribute)
matching_attributes(attribute).max do |a1, a2|
(a1.original_attribute / attribute) <=> (a2.original_attribute / attribute)
end
end
private
def matching_attributes(attribute)
(@matching_attributes ||= attributes.inject({}) do |hash, a|
(hash[a.root] ||= []) << a
hash
end)[attribute.root] || []
end
def has_attribute?(attribute)
!matching_attributes(attribute).empty?
end
end
include AttributeAccessable
module DefaultOperations
def attributes; [] end
def wheres; [] 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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