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Diffstat (limited to 'activerecord/lib/arel/visitors/oracle.rb')
| -rw-r--r-- | activerecord/lib/arel/visitors/oracle.rb | 159 |
1 files changed, 159 insertions, 0 deletions
diff --git a/activerecord/lib/arel/visitors/oracle.rb b/activerecord/lib/arel/visitors/oracle.rb new file mode 100644 index 0000000000..f96bf65ee5 --- /dev/null +++ b/activerecord/lib/arel/visitors/oracle.rb @@ -0,0 +1,159 @@ +# frozen_string_literal: true + +module Arel # :nodoc: all + 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) + + if offset.expr.is_a? Nodes::BindParam + collector << ") raw_sql_ WHERE rownum <= (" + collector = visit offset.expr, collector + collector << " + " + collector = visit limit, collector + collector << ") ) WHERE raw_rnum_ > " + collector = visit offset.expr, collector + return collector + else + collector << ") raw_sql_ + WHERE rownum <= #{offset.expr.to_i + limit} + ) + WHERE " + return visit(offset, collector) + end + 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.to_s + end + i += 1 if array[i].count("(") == array[i].count(")") + end + array + end + + def visit_Arel_Nodes_BindParam(o, collector) + collector.add_bind(o.value) { |i| ":a#{i}" } + end + + def is_distinct_from(o, collector) + collector << "DECODE(" + collector = visit [o.left, o.right, 0, 1], collector + collector << ")" + end + end + end +end |