felipecrv commented on code in PR #15083:
URL: https://github.com/apache/arrow/pull/15083#discussion_r1063480145
##########
cpp/src/arrow/compute/exec/aggregate.cc:
##########
@@ -121,21 +129,36 @@ Result<Datum> GroupBy(const std::vector<Datum>&
arguments, const std::vector<Dat
ExecSpanIterator argument_iterator;
ExecBatch args_batch;
- if (!arguments.empty()) {
+ if (!aggregates.empty()) {
ARROW_ASSIGN_OR_RAISE(args_batch, ExecBatch::Make(arguments));
// Construct and initialize HashAggregateKernels
- auto argument_types = args_batch.GetTypes();
+ std::vector<std::vector<TypeHolder>>
aggs_argument_types(aggregates.size());
+ {
+ // Contains the flattened list of aggregate arguments. We use the size of
+ // each Aggregate::target to re-group the aggregate argument types.
+ auto argument_types = args_batch.GetTypes();
Review Comment:
It can't be a reference because `GetTypes` doesn't return a reference.
(Technically it can, but won't really prevent the construction of the vector
within the stack).
I think moving the elements from the vector like this will give us more:
`TypeHolder` contains a `shared_ptr` -- cheaper to move than to copy.
```diff
for (size_t j = 0; j < aggregates.size(); j++) {
const size_t num_agg_args = aggregates[j].target.size();
for (size_t k = 0; k < num_agg_args && i < argument_types.size();
k++, i++) {
- aggs_argument_types[j].push_back(argument_types[i]);
+ aggs_argument_types[j].push_back(std::move(argument_types[i]));
}
}
```
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