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https://issues.apache.org/jira/browse/CALCITE-6869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17932551#comment-17932551
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Stamatis Zampetakis commented on CALCITE-6869:
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It seems a bit arbitrary to add a comment in the javadoc of a single rule when
there are many places in the code where we create project operators and thus
there is the likelihood of losing aliases. If we want to improve the
documentation we should rather do it at
https://calcite.apache.org/docs/algebra.html but as far as I see there are
already some mentions about it.
{noformat}
But if a relational expression has passed through several rewrite rules (see
RelOptRule), the field names of the resulting expression might not look much
like the originals. At that point it is better to reference fields by ordinal.
{noformat}
If we need improvements I believe the best place to do them is there and not
start touching every rule that handles projections.
> Add instructions for the alias loss problem in ProjectRemoveRule
> ----------------------------------------------------------------
>
> Key: CALCITE-6869
> URL: https://issues.apache.org/jira/browse/CALCITE-6869
> Project: Calcite
> Issue Type: Improvement
> Reporter: Zhen Chen
> Assignee: Zhen Chen
> Priority: Minor
> Labels: pull-request-available
>
> We should add a description of the alias loss problem and the current calcite
> solution in ProjectRemoveRule to avoid this issue being raised again.
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