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module Arel
class Relation
def to_sql(formatter = Sql::SelectStatement.new(self))
formatter.select select_sql, self
end
def select_sql
if engine.adapter_name == "PostgreSQL" && !orders.blank? && using_distinct_on?
# PostgreSQL does not allow arbitrary ordering when using DISTINCT ON, so we work around this
# by wrapping the +sql+ string as a sub-select and ordering in that query.
order = order_clauses.join(', ').split(',').map { |s| s.strip }.reject(&:blank?)
order = order.zip((0...order.size).to_a).map { |s,i| "id_list.alias_#{i} #{'DESC' if s =~ /\bdesc$/i}" }.join(', ')
query = build_query \
"SELECT #{select_clauses.kind_of?(::Array) ? select_clauses.join("") : select_clauses.to_s}",
"FROM #{from_clauses}",
(joins(self) unless joins(self).blank? ),
("WHERE #{where_clauses.join("\n\tAND ")}" unless wheres.blank? ),
("GROUP BY #{group_clauses.join(', ')}" unless groupings.blank? ),
("#{locked}" unless locked.blank? )
build_query \
"SELECT * FROM (#{query}) AS id_list",
"ORDER BY #{order}",
("LIMIT #{taken}" unless taken.blank? ),
("OFFSET #{skipped}" unless skipped.blank? )
else
build_query \
"SELECT #{select_clauses.join(', ')}",
"FROM #{from_clauses}",
(joins(self) unless joins(self).blank? ),
("WHERE #{where_clauses.join("\n\tAND ")}" unless wheres.blank? ),
("GROUP BY #{group_clauses.join(', ')}" unless groupings.blank? ),
("ORDER BY #{order_clauses.join(', ')}" unless orders.blank? ),
("LIMIT #{taken}" unless taken.blank? ),
("OFFSET #{skipped}" unless skipped.blank? ),
("#{locked}" unless engine.adapter_name =~ /SQLite/ || locked.blank?)
end
end
def inclusion_predicate_sql
"IN"
end
def christener
@christener ||= Sql::Christener.new
end
protected
def build_query(*parts)
parts.compact.join(" ")
end
def from_clauses
sources.blank? ? table_sql(Sql::TableReference.new(self)) : sources
end
def select_clauses
attributes.collect { |a| a.to_sql(Sql::SelectClause.new(self)) }
end
def where_clauses
wheres.collect { |w| w.to_sql(Sql::WhereClause.new(self)) }
end
def group_clauses
groupings.collect { |g| g.to_sql(Sql::GroupClause.new(self)) }
end
def order_clauses
orders.collect { |o| o.to_sql(Sql::OrderClause.new(self)) }
end
def using_distinct_on?
select_clauses.any? { |x| x =~ /DISTINCT ON/ }
end
end
end
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