[jira] [Commented] (PHOENIX-1854) Investigate not setting ProjectedColumnExpression in TupleProjector expressions array

["James Taylor (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PHOENIX-1854?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15114091#comment-15114091 ] 

James Taylor commented on PHOENIX-1854:
---------------------------------------

Is this necessary, [~maryannxue]? If not, please close.

> Investigate not setting ProjectedColumnExpression in TupleProjector expressions array
> -------------------------------------------------------------------------------------
>
>                 Key: PHOENIX-1854
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-1854
>             Project: Phoenix
>          Issue Type: Improvement
>            Reporter: James Taylor
>            Assignee: Maryann Xue
>            Priority: Minor
>             Fix For: 4.8.0
>
>
> In implementing PHOENIX-1826, on the visit of a ProjectedColumnExpression, we dereference the TupleProjector expressions array and continue the visit on the expression. To prevent a stack overflow due to infinite recursion, we detect the case when the dereferenced ProjectedColumnExpression is the same as the expression being visited and do not continue the traversal.  See FIXME in OrderPreservingTracker.TrackOrderPreservingExpressionVisitor:
> {code}
>         @Override
>         public Info visit(ProjectedColumnExpression node) {
>             if (projector == null) {
>                 return super.visit(node);
>             }
>             Expression expression = projector.getExpressions()[node.getPosition()];
>             // FIXME: prevents infinite recursion for union all in subquery, but
>             // should a ProjectedColumnExpression be used in this case? Wouldn't
>             // it make more sense to not create this wrapper in this case?
>             if (expression == node) {
>                 return super.visit(node);
>             }
>             return expression.accept(this);
>         }
> {code}
> It's possible that this wrapping is not necessary in the first place.



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