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https://issues.apache.org/jira/browse/CALCITE-7059?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17980047#comment-17980047
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Stamatis Zampetakis commented on CALCITE-7059:
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I haven't fully reviewed the RelFieldTrimmer class to evaluate the feasibility
of the proposal but wanted to keep my thoughts somewhere in case I find time to
push this forward in the future.
> Generalize RelFieldTrimmer to handle plans with arbitrary operators
> -------------------------------------------------------------------
>
> Key: CALCITE-7059
> URL: https://issues.apache.org/jira/browse/CALCITE-7059
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.40.0
> Reporter: Stamatis Zampetakis
> Priority: Major
>
> Currently the
> [RelFieldTrimmer|https://github.com/apache/calcite/blob/597b1fd54fe5b8586525aed2bc4518ca54a25523/core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java]
> class is mostly tailored to handle plans using the built-in {{LogicalXx}}
> operators. Still there are many projects that have their own flavor of
> "logical" operators, which do not differ much from the built-in when it comes
> to field trimming, and are forced to extend or copy the trimmer code in order
> to use it.
> To further expand the usage of the trimmer and minimize unnecessary
> extensions we could envision the following enhancements.
> *Refactor references/usages of LogicalXx operators*
> In most cases a {{Logical}} operator is extending another more abstract one
> so we could favor the use of the abstract one in every place where a logical
> one is used.
> *Use {{RelNode#copy}} instead of the {{RelBuilder}} to create the new
> (trimmed) expressions*
> The trimmer currently makes use of a {{RelBuilder}} in various places to
> create the new operators. There are advantages in using the RelBuilder but
> when plans mix operators from different conventions (e.g., Enumerable and
> Jdbc) the builder and subsequently the trimmer cannot be used; the old and
> the new (trimmed) operator must be in the same convention.
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