mbutrovich commented on code in PR #4557:
URL: https://github.com/apache/datafusion-comet/pull/4557#discussion_r3349573678
##########
spark/src/main/scala/org/apache/comet/codegen/CometBatchKernelCodegen.scala:
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@@ -401,10 +401,15 @@ object CometBatchKernelCodegen extends Logging with
CometExprTraitShim {
* True iff every node in the tree propagates nulls (`NullIntolerant`,
`BoundReference`, or
* `Literal`). Gates the [[defaultBody]] short-circuit, which is only
correct when no node
* (`Coalesce`, `If`, `CaseWhen`, `Concat`, ...) breaks the propagation
chain.
+ *
+ * `TryEval` is rejected: it is `NullIntolerant` (null input -> null
output), but its
+ * `doGenCode` also yields null on non-null input when the child throws. The
short-circuit
+ * assumes non-null inputs imply non-null output and would feed a null
`ev.value` to the writer.
*/
private def allNullIntolerant(expr: Expression): Boolean =
!expr.exists {
case _: BoundReference | _: Literal => false
+ case _: TryEval => true
Review Comment:
This and #4579 are fixing the same latent bug in the codegen dispatcher's
NullIntolerant short-circuit. Both expose the case where an expression reports
`nullIntolerant=true` but can still emit null on non-null inputs: `TryEval`
here via the caught exception, `MakeTimestamp(failOnError=false)` in #4579 via
the caught `DateTimeException`. In both the short-circuit's else branch wrote
`ev.value` without re-checking `ev.isNull`.
I just approved #4579. Its fix is the general one: it keeps the null-input
fast skip and re-adds the post-eval `if (ev.isNull) setNull else write` guard
for any nullable NullIntolerant root, so it already covers `try_aes_decrypt`
(the `TryEval` root is nullable, and `TryEval.doGenCode` sets `ev.isNull=true`
on the caught exception, so the guarded write skips the binary writer and the
NPE never happens).
Once #4579 lands, the `allNullIntolerant`-rejects-`TryEval` change in
`CometBatchKernelCodegen.scala` here is redundant. Worse, it pushes `TryEval`
trees out of the now-correct short-circuit onto the default path, which loses
the null-input fast skip for no correctness benefit. Could you rebase on #4579
and drop the `CometBatchKernelCodegen.scala` edit, keeping the serde additions
(`statics.scala`, `QueryPlanSerde.scala`) and the SQL fixtures? That keeps the
two PRs from conflicting on `CometBatchKernelCodegen.scala`.
One thing I checked: the only AES path that produces null on non-null input
is the `TryEval` one, which is nullable, so #4579's guard engages. The non-try
`aes_decrypt` / `aes_encrypt` throw on bad input rather than returning null,
matching Spark, so the non-nullable direct-write path stays correct for those.
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