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https://issues.apache.org/jira/browse/TAJO-895?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Hyunsik Choi reassigned TAJO-895:
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Assignee: Hyunsik Choi
> ConstEval should not be included in target list of projectable nodes
> --------------------------------------------------------------------
>
> Key: TAJO-895
> URL: https://issues.apache.org/jira/browse/TAJO-895
> Project: Tajo
> Issue Type: Improvement
> Components: planner/optimizer
> Reporter: Hyunsik Choi
> Assignee: Hyunsik Choi
>
> In some applications, aliased constant values can be used in WHERE, GROUP BY,
> HAVING, ORDER BY clauses. For those cases, current planner evaluates constant
> value in target list of projectable nodes.
> {code}
> SELECT '1994' end as year, ... FROM lineitem WHERE group by year;
> {code}
> This approach works well so far, but there are rooms for significant
> improvement.
> The main problem is that constant target requires many workaround code in
> NamedExprManager, and TargetListManager. As a result, it makes code
> complexity higher. The second problem is that many constant values evaluated
> in each row consume unnecessary I/O and network bandwidth for storing and
> transmitting.
> The solution seems to be simple. In logical planning phase, we should rewrite
> column references which actually indicates constant values.
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