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https://issues.apache.org/jira/browse/CALCITE-4784?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17417576#comment-17417576
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Stamatis Zampetakis commented on CALCITE-4784:
----------------------------------------------
There is already an {{assert isValid(...)}} call in the constructor of the
{{Correlate}} and in the constructors of other relational expressions so I am
inclined to keep the new check inside {{isValid}} method mostly for keeping
things uniform.
> 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: 20m
> 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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