[TAJO-539] Change some EvalNode::eval to directly return a Datum value

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.8.0
• Component/s: Expression
• Assignee: Hyunsik Choi
• Reporter: Hyunsik Choi
• Created: 21/Jan/14 07:09
• Updated: 25/Jan/14 11:40
• Resolved: 25/Jan/14 06:35

Description

After TAJO-501, we can ensure that all expressions except for AggregationFunctionCallEval can be evaluated by calling once eval() instead of calling eval followed by terminate. In addition, current EvalNode implementation involves unnecessary memory consumption to keep EvalContext for all expressions which are not even aggregation eval.

If we change EvalNode::eval() to directly return a Datum value, it would reduce the memory consumption and CPU costs.