[jira] [Created] (CALCITE-6368) Inconsistent handling of COALESCE during validation

["Claude Brisson (Jira)" <ji...@apache.org>]

Claude Brisson created CALCITE-6368:
---------------------------------------

             Summary: Inconsistent handling of COALESCE during validation
                 Key: CALCITE-6368
                 URL: https://issues.apache.org/jira/browse/CALCITE-6368
             Project: Calcite
          Issue Type: Bug
          Components: core
    Affects Versions: 1.36.0
            Reporter: Claude Brisson


{{SqlCoalesceFunction}} has a {{rewriteCall()}} method which will replace the call with an {{SqlCase}} call during the unconditional rewrites stage.

But expanding natural joins and {{USING}} conditions is done using {{COALESCE}} calls in a later validation stage.

As a result, the following query:

{code}
WITH A AS (SELECT 1 AS X)
  SELECT
    COALESCE(A0.X, A1.X),
    *
  FROM A AS A0 NATURAL JOIN A AS A1
{code}

is transformed by the validation step into:

{code}
WITH `A` AS (SELECT 1 AS `X`)
  SELECT
    CASE WHEN `A0`.`X` IS NOT NULL THEN `A0`.`X` ELSE `A1`.`X` END, 
    COALESCE(`A0`.`X`, `A1`.`X` AS `X0`) AS `X`
  FROM `A` AS `A0` NATURAL INNER JOIN `A` AS `A1`
{code}

Maybe, the expanded results of {{*}} with natural joins and of {{USING}} should pass through unconditional rewrites at creation.





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