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|
module Arel
module Visitors
class Oracle < Arel::Visitors::ToSql
private
def visit_Arel_Nodes_SelectStatement o, collector
o = order_hacks(o)
# if need to select first records without ORDER BY and GROUP BY and without DISTINCT
# then can use simple ROWNUM in WHERE clause
if o.limit && o.orders.empty? && o.cores.first.groups.empty? && !o.offset && o.cores.first.set_quantifier.class.to_s !~ /Distinct/
o.cores.last.wheres.push Nodes::LessThanOrEqual.new(
Nodes::SqlLiteral.new('ROWNUM'), o.limit.expr
)
return super
end
if o.limit && o.offset
o = o.dup
limit = o.limit.expr
offset = o.offset
o.offset = nil
collector << "
SELECT * FROM (
SELECT raw_sql_.*, rownum raw_rnum_
FROM ("
collector = super(o, collector)
collector << ") raw_sql_
WHERE rownum <= #{offset.expr.to_i + limit}
)
WHERE "
return visit(offset, collector)
end
if o.limit
o = o.dup
limit = o.limit.expr
collector << "SELECT * FROM ("
collector = super(o, collector)
collector << ") WHERE ROWNUM <= "
return visit limit, collector
end
if o.offset
o = o.dup
offset = o.offset
o.offset = nil
collector << "SELECT * FROM (
SELECT raw_sql_.*, rownum raw_rnum_
FROM ("
collector = super(o, collector)
collector << ") raw_sql_
)
WHERE "
return visit offset, collector
end
super
end
def visit_Arel_Nodes_Limit o, collector
collector
end
def visit_Arel_Nodes_Offset o, collector
collector << "raw_rnum_ > "
visit o.expr, collector
end
def visit_Arel_Nodes_Except o, collector
collector << "( "
collector = infix_value o, collector, " MINUS "
collector << " )"
end
def visit_Arel_Nodes_UpdateStatement o, collector
# Oracle does not allow ORDER BY/LIMIT in UPDATEs.
if o.orders.any? && o.limit.nil?
# However, there is no harm in silently eating the ORDER BY clause if no LIMIT has been provided,
# otherwise let the user deal with the error
o = o.dup
o.orders = []
end
super
end
###
# Hacks for the order clauses specific to Oracle
def order_hacks o
return o if o.orders.empty?
return o unless o.cores.any? do |core|
core.projections.any? do |projection|
/FIRST_VALUE/ === projection
end
end
# Previous version with join and split broke ORDER BY clause
# if it contained functions with several arguments (separated by ',').
#
# orders = o.orders.map { |x| visit x }.join(', ').split(',')
orders = o.orders.map do |x|
string = visit(x, Arel::Collectors::SQLString.new).value
if string.include?(',')
split_order_string(string)
else
string
end
end.flatten
o.orders = []
orders.each_with_index do |order, i|
o.orders <<
Nodes::SqlLiteral.new("alias_#{i}__#{' DESC' if /\bdesc$/i === order}")
end
o
end
# Split string by commas but count opening and closing brackets
# and ignore commas inside brackets.
def split_order_string(string)
array = []
i = 0
string.split(',').each do |part|
if array[i]
array[i] << ',' << part
else
# to ensure that array[i] will be String and not Arel::Nodes::SqlLiteral
array[i] = '' << part
end
i += 1 if array[i].count('(') == array[i].count(')')
end
array
end
def visit_Arel_Nodes_BindParam o, collector
collector.add_bind(o) { |i| ":a#{i}" }
end
end
end
end
|
