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https://issues.apache.org/jira/browse/CALCITE-1943?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16127038#comment-16127038
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Dian Fu commented on CALCITE-1943:
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In one word, if we don't transform {{A.net_weight}} to {{PREV(A.net_weight,
0)}}, it will make it difficult to implement the following method in
{{RexVisitor}}.
{code}
R visitPatternFieldRef(RexPatternFieldRef fieldRef);
{code}
If the return result of this method is the specified field of the element, then
the negation will be impossible. If not, the comparation of {{A.net_weight >
PREV(B.net_weight, 1)}} will make non sense.
> Add back NavigationExpander and NavigationReplacer in SqlValidatorImpl
> ----------------------------------------------------------------------
>
> Key: CALCITE-1943
> URL: https://issues.apache.org/jira/browse/CALCITE-1943
> Project: Calcite
> Issue Type: Bug
> Reporter: Dian Fu
> Assignee: Julian Hyde
>
> {{NavigationExpander}} and {{NavigationReplacer}} was deleted as a fix of
> issue CALCITE-1871. Just create this ticket to track whether we should add
> them back.
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