[jira] [Created] (SPARK-59579) Keep the conditional-branch guards after the subexpression elimination shortcut peel

["Yang Jie (Jira)" <ji...@apache.org>]

Yang Jie created SPARK-59579:
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             Summary: Keep the conditional-branch guards after the subexpression elimination shortcut peel
                 Key: SPARK-59579
                 URL: https://issues.apache.org/jira/browse/SPARK-59579
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 5.0.0
            Reporter: Yang Jie


{{EquivalentExpressions.childrenToRecurse}} stops the descent for expressions whose children must not be evaluated ahead of time: {{CodegenFallback}}, {{ConditionalExpression}} (only {{alwaysEvaluatedInputs}} are recursed into) and {{HigherOrderFunction}}.

When {{spark.sql.subexpressionElimination.skipForShortcutExpr}} is enabled, {{skipForShortcut}} first peels the leading {{And}}/{{Or}} operands to reach the one operand that is always evaluated. {{And}}/{{Or}} are not {{ConditionalExpression}}s, so the peel walks past those cases, and the code then took {{peeled.children}} directly -- recursing into every child of the expression the peel landed on, conditional branches included.

Repro, with ANSI mode on and both {{spark.sql.subexpressionElimination.enabled}} and {{spark.sql.subexpressionElimination.skipForShortcutExpr}} set to true:

{code:sql}
select (case when id = 0 then false else (1 / id + 1 / id) > 0 end) and id >= 0
from range(0, 1, 1, 1)
{code}

{{1 / id}} is repeated inside one branch body only, so it is shared with no other branch and should be evaluated only when that branch runs. For id = 0 the other branch runs. Instead {{1 / id}} is collected as a common subexpression, hoisted to the top of the projection and evaluated for id = 0, raising DIVIDE_BY_ZERO.

The fix is to compute the always-evaluated operand once and ask both {{childrenToRecurse}} and {{commonChildrenToRecurse}} about that operand. Only the {{skipForShortcutExpr}} path changes, and the config default (false) stays.




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