[jira] [Commented] (CALCITE-4784) Ensure Correlate#requiredColumns is subset of columns in left relation

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

    [ https://issues.apache.org/jira/browse/CALCITE-4784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17416759#comment-17416759 ] 

Julian Hyde commented on CALCITE-4784:
--------------------------------------

If it’s a quick check, consider making it a precondition in the constructor. Invariants are good.

> Ensure Correlate#requiredColumns is subset of columns in left relation
> ----------------------------------------------------------------------
>
>                 Key: CALCITE-4784
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4784
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: Stamatis Zampetakis
>            Assignee: Stamatis Zampetakis
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.28.0
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> The {{Correlate}} [expression|https://github.com/apache/calcite/blob/f3baf348598fcc6bc4f97a0abee3f99309e5bf76/core/src/main/java/org/apache/calcite/rel/core/Correlate.java] has among others a field ({{requiredColumns}} for representing the set of columns that are used by the correlation.
> {code:java}
> public abstract class Correlate extends BiRel {
>   protected final CorrelationId correlationId;
>   protected final ImmutableBitSet requiredColumns;
>   protected final JoinRelType joinType;
>   /**
>    * Returns the required columns in left relation required for the correlation
>    * in the right.
>    *
>    * @return columns in left relation required for the correlation in the right
>    */
>   public ImmutableBitSet getRequiredColumns() {
>     return requiredColumns;
>   }
> {code}
> As the javadoc indicates (implicitly) these columns must be a subset of the columns of the left relation. This is currently not enforced when creating a correlation which can lead to invalid plans and runtime failures which are hard to investigate.
> I propose to introduce an additional check inside {{Correlate#isValid}} method for enforcing that required columns are valid.



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