[jira] [Created] (CALCITE-4222) Clarify if null elements are allowed in RelTraitSet

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

Vladimir Sitnikov created CALCITE-4222:
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             Summary: Clarify if null elements are allowed in RelTraitSet
                 Key: CALCITE-4222
                 URL: https://issues.apache.org/jira/browse/CALCITE-4222
             Project: Calcite
          Issue Type: Sub-task
          Components: core
    Affects Versions: 1.25.0
            Reporter: Vladimir Sitnikov


Currently, one-half of the methods in {{RelTraitSet}} fails with NPE, and another half does have some null-checks. Then there are {{getDefault()}} and {{isDefault()}}

AFAIK the only way to create a traitset with null element currently is to implement {{org.apache.calcite.plan.RelTraitDef#getDefault}} to return {{null}} (which never happens in Calcite code).
However, such a traitset would likely fail with NPE in {{org.apache.calcite.plan.RelTraitSet#satisfies}} quite fast.

{{RelCollationTraitDef}} and {{RelDistributionTraitDef}} have non-null default value which might interfere with collation and distribution metadata. For instance, {{distribution}} metadata might return null, and then it would fail with NPE when replacing distribution trait.




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