bkietz commented on code in PR #39908:
URL: https://github.com/apache/arrow/pull/39908#discussion_r1476439011
##########
cpp/src/arrow/compute/expression.cc:
##########
@@ -750,15 +750,23 @@ Result<Datum> ExecuteScalarExpression(const Expression&
expr, const ExecBatch& i
auto call = CallNotNull(expr);
- std::vector<Datum> arguments(call->arguments.size());
-
+ size_t num_args = call->arguments.size();
+ std::vector<Datum> arguments(num_args);
bool all_scalar = true;
- for (size_t i = 0; i < arguments.size(); ++i) {
- ARROW_ASSIGN_OR_RAISE(
- arguments[i], ExecuteScalarExpression(call->arguments[i], input,
exec_context));
- if (arguments[i].is_array()) {
- all_scalar = false;
+
+ if (num_args) {
Review Comment:
I'd prefer to see this special case produce an input length rather than
modify all_scalar, to make the goal more clear:
```suggestion
std::vector<Datum> arguments(call->arguments.size());
bool all_scalar = true;
for (size_t i = 0; i < arguments.size(); ++i) {
ARROW_ASSIGN_OR_RAISE(
arguments[i], ExecuteScalarExpression(call->arguments[i], input,
exec_context));
if (arguments[i].is_array()) {
all_scalar = false;
}
}
int64_t input_length;
if (!arguments.empty() && all_scalar) {
// all inputs are scalar, so use a 1-long batch to avoid
// computing input.length equivalent outputs
input_length = 1;
} else {
input_length = input.length;
}
```
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