xuzifu666 commented on code in PR #5384:
URL: https://github.com/apache/calcite/pull/5384#discussion_r4455243398
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core/src/main/java/org/apache/calcite/rex/RexUtil.java:
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@@ -1823,20 +1832,44 @@ private static boolean isFlat(
* calls to an associative operator such as AND and OR.
*/
public static boolean isFlat(RexNode expr) {
- if (!(expr instanceof RexCall)) {
- return true;
+ // Use an explicit stack to avoid StackOverflowError on deeply nested
+ // expressions (e.g. CALCITE-5845)
+ final Deque<RexNode> stack = new ArrayDeque<>();
+ stack.push(expr);
+ while (!stack.isEmpty()) {
+ final RexNode current = stack.pop();
+ if (!(current instanceof RexCall)) {
+ continue;
+ }
+ final RexCall call = (RexCall) current;
+ if (!isFlat(call.getOperands(), call.getOperator())) {
Review Comment:
It's non-recursive and it only loops over an explicit `ArrayDeque`, and the
private list overload is the original non-recursive exists() check.
testIsFlatDeeplyNested verifies it: overflows against the old code on a 256KB
stack, passes in latest commit.
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