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https://issues.apache.org/jira/browse/CALCITE-5984?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17763250#comment-17763250
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Julian Hyde commented on CALCITE-5984:
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I don't know. If there is a sane way to prevent trimming, please contribute it.
And contribute tests to demonstrate that trimming does not occur.
If there are some rules that cannot operate without trimming (I don't know,
just speculating) then I guess those rules would need to be disabled.
> Cannot fully disable trimming unused fields using Calcite configs
> -----------------------------------------------------------------
>
> Key: CALCITE-5984
> URL: https://issues.apache.org/jira/browse/CALCITE-5984
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.34.0
> Reporter: Wegdan Ghazi
> Priority: Major
>
> In Prepare#prepareSql there are 2 instances of trimming unused fields
> 1.
> [Prepare#trimUnusedFields|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/prepare/Prepare.java#L375]
> called
> [here|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/prepare/Prepare.java#L297]
>
> {code:java}
> // Trim unused fields.
> root = trimUnusedFields(root); {code}
> 2.
> {color:#172b4d}[TrimFieldsProgram|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/tools/Programs.java#L369]{color}
> called
> [here|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/prepare/Prepare.java#L312]
> within
> {code:java}
> root = optimize(root, getMaterializations(), getLattices());
> {code}
> I want to turn of the field trimming due to a personalisation I'm
> implementing to scan a specific API, which I would think is possible using
> [SqlConverter.Config|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/sql2rel/SqlToRelConverter.java#L6085C20-L6085C26]
> I attempted to disable the trimming using hooks [PROGRAM,
> SQL2REL_CONVERTER_CONFIG_BUILDER], which succeeded to remove the trimming
> program, yet on
> [Prepare#trimUnusedFields|https://github.com/apache/calcite/blob/64268b9dd70bcdc15a3421ab120b8e5ecba17339/core/src/main/java/org/apache/calcite/prepare/Prepare.java#L375]
> {code:java}
> // code placehprotected RelRoot trimUnusedFields(RelRoot root) {
> final SqlToRelConverter.Config config = SqlToRelConverter.config()
> .withTrimUnusedFields(shouldTrim(root.rel))
> .withExpand(THREAD_EXPAND.get())
>
> .withInSubQueryThreshold(castNonNull(THREAD_INSUBQUERY_THRESHOLD.get()));
> final SqlToRelConverter converter =
> getSqlToRelConverter(getSqlValidator(), catalogReader, config);
> final boolean ordered = !root.collation.getFieldCollations().isEmpty();
> final boolean dml = SqlKind.DML.contains(root.kind);
> return root.withRel(converter.trimUnusedFields(dml || ordered, root.rel));
> }
> {code}
> The config passed (and edited by the hook) gets overwritten and only
> _shouldTrim(root.rel)_ can enable/disable trimming, I would expect this to
> happen iff the config _withTrimUnusedFields_ is only set to {_}true{_}.
> Is this the intended behaviour? Any help is appreciated, thanks.
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