[jira] [Commented] (CALCITE-6357) Calcite enforces select arguments count to be same as row schema fields which causes aliases to be ignored

["Julian Hyde (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-6357?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17835833#comment-17835833 ] 

Julian Hyde commented on CALCITE-6357:
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If the number of fields does not match, that's probably a problem on your end. {{RelBuilder}} almost always requires number of fields to match.

Regarding column aliases. Calcite generally doesn't promise to preserve aliases, but in some cases you can force a rename. At [RelBuilder#2125|https://github.com/apache/calcite/blob/f14cf4c32b9079984a988bbad40230aa6a59b127/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2125] it seems that {{force}} is false. For the behavior you want, {{force}} would need to be true.

> Calcite enforces select arguments count to be same as row schema fields which causes aliases to be ignored
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-6357
>                 URL: https://issues.apache.org/jira/browse/CALCITE-6357
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Brachi Packter
>            Priority: Major
>
> Calcite RelBuilder.ProjectNamed checks if row size in the select is identical to schema fields, if no, it creates a project with fields as they appear in the select , meaning if they have aliases, they are returning with their aliases.
> Here, it checks if they are identical:
> https://github.com/apache/calcite/blob/f14cf4c32b9079984a988bbad40230aa6a59b127/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2063
> using RexUtil.isIdentity method:
> ```
>  public static boolean isIdentity(List<? extends RexNode> exps,
>       RelDataType inputRowType) {
>     return inputRowType.getFieldCount() == exps.size()
>         && containIdentity(exps, inputRowType, Litmus.IGNORE);
>   }
> ```
> This is the problematic part `inputRowType.getFieldCount() == exps.size()`
> If they are identical, and return with their aliases, it is ignored in the "rename" method later on
> https://github.com/apache/calcite/blob/f14cf4c32b9079984a988bbad40230aa6a59b127/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2125
> and alias is skipped
> https://github.com/apache/calcite/blob/f14cf4c32b9079984a988bbad40230aa6a59b127/core/src/main/java/org/apache/calcite/tools/RelBuilder.java#L2137
> This doesn't impact calcite queries, but in Apache Beam they are doing some optimization on top of it, https://github.com/apache/beam/blob/master/sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/impl/rule/BeamAggregateProjectMergeRule.java
> which causes aliases to be ignored, and data is returning suddenly without correct column field.
> I believe the isIdentity check can causes more issues if not fixed, we need to understand why is it enforced? isn't it valid to have different size of fields in select from what we have in the schema?
> In our case we have a one big row and we run on it different queries, each with different fields in the select.
> Beam issue 
> https://github.com/apache/beam/issues/30498 



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