[TAJO-122] Add EXPLAIN clause to show a logical plan

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.8.0
• Component/s: Planner/Optimizer
• Assignee: DaeMyung Kang
• Reporter: Hyunsik Choi
• Created: 07/Aug/13 09:09
• Updated: 14/Jan/14 17:11
• Resolved: 14/Jan/14 17:08

Description

(I've changed this issue from implementing an utility class to preint JSON to implementing EXPLAIN clause support.)

For convenience for debugging and developing new engine (TAJO-104), we need EXPLAIN clause to print plans used in Tajo internal. In this issue, we only focus on showing a logical plan.