[TAJO-415] Some complex queries causes NPE and unlimited recursions.

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Fix Version/s: 0.8.0
• Component/s: distributed query plan, Planner/Optimizer
• Assignee: Hyunsik Choi
• Reporter: Hyunsik Choi
• Created: 14/Dec/13 04:35
• Updated: 15/Dec/13 16:03
• Resolved: 15/Dec/13 15:46

Description

This patch fixes the following critical bugs.

• GreedyHeuristicJoinOrder::getCost may cause unlimited recursion.
  • getCost() method is a recursion function.
  • getCost() method has not considered all logical operators, so some logical operators are processed in a default case which is implemented incorrectly. It causes unlimited recursion.
• ProjectionPushDown rewrite rule tries to push down necessary target lists to all subqueries.
  • It may cause some problem in a subquery which includes a group-by operator because there is no unnecessary target lists in the subquery, including a group-by operator. This patch prevents ProjectionPushDown to push down target lists to some subqueries.
• Task::setLogicalPlan does not traverse descendant nodes of TableSubQueryNode.
  • So, it have missed some logical operators.
• SubQuery::getInputVolume may cause NPE when a logical plan includes a bushy join tree.
  • In the past, a distributed plan is generated from left-deep join tree. At that time, the volume of join relations are computed directly from joined results (left) or relation nodes (right). However, for bushy join, getInputVolume() has some cases to estimate intermediate data volume prior to actual joins.
• FilterPushDown tries to validate outer join's null suppression. This code assumes that outer join's input relations are only ScanNodes.
  • Actually, outer join's input relations can be either ScanNode or TableSubQueryNode.