Merge pull request #450 from roooodcastro/issue-438

Use Arel::Nodes::BindParam in Oracle visitor for queries using both LIMIT and OFFSET

Author: rafaelfranca

lib/arel/visitors/oracle.rb

@@ -26,11 +26,22 @@ def visit_Arel_Nodes_SelectStatement o, collector
                 FROM ("
 
           collector = super(o, collector)
-          collector << ") raw_sql_
+
+          if offset.expr.is_a? Nodes::BindParam
+            offset_bind = nil
+            collector << ') raw_sql_ WHERE rownum <= ('
+            collector.add_bind(offset.expr) { |i| offset_bind = ":a#{i}" }
+            collector << ' + '
+            collector.add_bind(limit) { |i| ":a#{i}" }
+            collector << ") ) WHERE raw_rnum_ > #{offset_bind}"
+            return collector
+          else
+            collector << ") raw_sql_
                 WHERE rownum <= #{offset.expr.to_i + limit}
               )
               WHERE "
-          return visit(offset, collector)
+            return visit(offset, collector)
+          end
         end
 
         if o.limit

test/visitors/test_oracle.rb

@@ -124,6 +124,21 @@ def compile node
             }
           end
 
+          it 'creates a subquery when there is limit and offset with BindParams' do
+            stmt = Nodes::SelectStatement.new
+            stmt.limit = Nodes::Limit.new(Nodes::BindParam.new)
+            stmt.offset = Nodes::Offset.new(Nodes::BindParam.new)
+            sql = compile stmt
+            sql.must_be_like %{
+              SELECT * FROM (
+                SELECT raw_sql_.*, rownum raw_rnum_
+                FROM (SELECT ) raw_sql_
+                 WHERE rownum <= (:a1 + :a2)
+              )
+              WHERE raw_rnum_ > :a1
+            }
+          end
+
           it 'is idempotent with different subquery' do
             stmt = Nodes::SelectStatement.new
             stmt.limit = Nodes::Limit.new(10)
@@ -148,7 +163,6 @@ def compile node
             }
           end
         end
-
       end
 
       it 'modified except to be minus' do