brucearctor commented on code in PR #69938:
URL: https://github.com/apache/doris/pull/69938#discussion_r4446644702
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/PushDownProject.java:
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@@ -338,6 +342,53 @@ private static List<NamedExpression> replaceSlot(
return pushedOutput;
}
+ /**
+ * Returns true if {@code expression} references any {@link ArrayItemSlot}
that is not bound
+ * by an enclosing {@link Lambda} within {@code expression} itself.
+ *
+ * <p>{@link Expression#getInputSlots()} deliberately excludes {@link
ArrayItemSlot}, so a
+ * sub-expression inside a lambda body (such as {@code element_at(p, 1)})
has an empty
+ * {@code getInputSlots()} set when it only depends on the lambda
parameter {@code p}.
+ * Pushing such a sub-expression out of its enclosing {@link Lambda} into
a child
+ * {@link LogicalProject} leaves {@code p} unbound outside {@code
visitArrayMap}, causing
+ * {@code ExpressionTranslator.visitArrayItemSlot} to return {@code null}.
+ */
+ @VisibleForTesting
+ static boolean hasFreeLambdaArgument(Expression expression) {
+ return hasFreeLambdaArgument(expression, ImmutableSet.of());
+ }
+
+ private static boolean hasFreeLambdaArgument(Expression expression,
Set<ExprId> boundLambdaArgs) {
+ if (!expression.containsType(ArrayItemSlot.class)) {
+ return false;
+ }
+ if (expression instanceof ArrayItemSlot) {
+ return !boundLambdaArgs.contains(((ArrayItemSlot)
expression).getExprId());
+ }
+ if (expression instanceof Lambda) {
+ Lambda lambda = (Lambda) expression;
+ // The array expression iterated by each lambda argument is
evaluated in the outer scope,
+ // before this lambda's own parameters are bound.
+ for (ArrayItemReference arg : lambda.getLambdaArguments()) {
+ if (hasFreeLambdaArgument(arg.getArrayExpression(),
boundLambdaArgs)) {
+ return true;
+ }
+ }
+ ImmutableSet.Builder<ExprId> nextBoundArgs =
ImmutableSet.<ExprId>builder()
+ .addAll(boundLambdaArgs);
Review Comment:
Addressed in be7eac6c:
1. Check `child.getOutputSet().containsAll(e.getInputSlots())` before
calling `hasFreeLambdaArgument(e)` (and `break` out of the child loop if
`hasFreeLambdaArgument(e)` is true), so cross-child candidates skip the lambda
scope scan entirely.
2. Track bound lambda parameter `ExprId`s with a single mutable
`HashSet<ExprId>` using scoped add/remove (`try ... finally`) instead of
copying `ImmutableSet` at each nested `Lambda`.
3. Added a deeply nested lambda chain test case in
`PushDownProjectTest#testHasFreeLambdaArgument`.
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