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

["Stamatis Zampetakis (Jira)" <ji...@apache.org>]

Stamatis Zampetakis created CALCITE-4784:
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             Summary: 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
             Fix For: 1.28.0


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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