github-actions[bot] commented on code in PR #64293:
URL: https://github.com/apache/doris/pull/64293#discussion_r3379312883
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/CountLiteralRewrite.java:
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@@ -107,10 +114,29 @@ private boolean isCountLiteral(AggregateFunction aggFunc)
{
&& aggFunc.child(0).isLiteral();
}
+ private boolean isCountConstantExpression(AggregateFunction aggFunc) {
+ if (aggFunc.isDistinct()
+ || !(aggFunc instanceof Count)
+ || aggFunc.children().size() != 1) {
+ return false;
+ }
+ Expression arg = aggFunc.child(0);
+ return !arg.isLiteral()
+ && arg.foldable()
+ && !arg.containsNondeterministic()
+ && !arg.containsVolatileExpression()
+ && arg.getInputSlots().isEmpty()
+ && !arg.containsType(AggregateFunction.class,
SubqueryExpr.class,
+ TableGeneratingFunction.class, WindowExpression.class);
+ }
+
private Expression rewrite(Count count) {
if (count.child(0).isNullLiteral()) {
return new BigIntLiteral(0);
Review Comment:
This rewrite changes empty-input aggregate semantics because it moves the
original count argument into an upper project. For example, on an empty table
`SELECT count(json_extract('{"id":123}', '$.')) FROM t` should not evaluate the
aggregate argument for any input row and should return `0`, but after this
rewrite the plan evaluates `json_extract(..., '$.') IS NULL` once above
`count(*)`, and JSON path validation raises `Invalid Json Path for value: $.`
even though the aggregate input is empty. The same applies to any deterministic
row-independent expression that can fail when evaluated. Please avoid
evaluating the original argument above the aggregate for the zero-row case, or
otherwise restrict the rewrite to expressions that are proven safe to evaluate
independently, and add an empty-table negative/positive regression case.
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