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module Arel
module Visitors
class Oracle < Arel::Visitors::ToSql
private
def visit_Arel_Nodes_SelectStatement o
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.offset && o.cores.first.projections.first !~ /^DISTINCT /
o.cores.last.wheres.push Nodes::LessThanOrEqual.new(
Nodes::SqlLiteral.new('ROWNUM'), o.limit
)
o.limit = nil
return super
end
if o.limit && o.offset
o = o.dup
limit = o.limit.to_i
offset = o.offset
o.limit = nil
o.offset = nil
sql = super(o)
return <<-eosql
SELECT * FROM (
SELECT raw_sql_.*, rownum raw_rnum_
FROM (#{sql}) raw_sql_
WHERE rownum <= #{offset.value.to_i + limit}
)
WHERE #{visit offset}
eosql
end
if o.limit
o = o.dup
limit = o.limit
o.limit = nil
return "SELECT * FROM (#{super(o)}) WHERE ROWNUM <= #{limit}"
end
if o.offset
o = o.dup
offset = o.offset
o.offset = nil
sql = super(o)
return <<-eosql
SELECT * FROM (
SELECT raw_sql_.*, rownum raw_rnum_
FROM (#{sql}) raw_sql_
)
WHERE #{visit offset}
eosql
end
super
end
def visit_Arel_Nodes_Offset o
"raw_rnum_ > #{visit o.value}"
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|
/DISTINCT.*FIRST_VALUE/ === projection
end
end
# FIXME: previous version with join and split broke ORDER BY clause
# if it contained functions with several arguments (separated by ',').
# Currently splitting is done only if there is no function calls
#
# orders = o.orders.map { |x| visit x }.join(', ').split(',')
orders = o.orders.map do |x|
string = visit x
# if there is function call
if string.include?('(')
string
# if no function call then comma splits several ORDER BY columns
elsif string.include?(',')
string.split(',')
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
end
end
end
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