pitrou commented on code in PR #45822:
URL: https://github.com/apache/arrow/pull/45822#discussion_r2003173724
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cpp/src/arrow/compute/row/grouper.cc:
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@@ -417,35 +433,91 @@ struct GrouperImpl : public Grouper {
RETURN_NOT_OK(encoders_[i]->Encode(batch[i], batch.length,
key_buf_ptrs.data()));
}
- TypedBufferBuilder<uint32_t> group_ids_batch(ctx_->memory_pool());
- RETURN_NOT_OK(group_ids_batch.Resize(batch.length));
+ using MapIterator = typename decltype(map_)::iterator;
- for (int64_t i = 0; i < batch.length; ++i) {
- int32_t key_length = offsets_batch[i + 1] - offsets_batch[i];
- std::string key(
- reinterpret_cast<const char*>(key_bytes_batch.data() +
offsets_batch[i]),
- key_length);
-
- auto it_success = map_.emplace(key, num_groups_);
- auto group_id = it_success.first->second;
-
- if (it_success.second) {
- // new key; update offsets and key_bytes
- ++num_groups_;
- // Skip if there are no keys
- if (key_length > 0) {
- auto next_key_offset = static_cast<int32_t>(key_bytes_.size());
- key_bytes_.resize(next_key_offset + key_length);
- offsets_.push_back(next_key_offset + key_length);
- memcpy(key_bytes_.data() + next_key_offset, key.c_str(), key_length);
+ struct LookupResult {
+ bool inserted;
+ bool found;
+ MapIterator it;
+ };
+
+ auto generate_keys = [&](auto&& lookup_key, auto&& visit_group,
Review Comment:
I'll try to, but given they also access local state, I don't know how
ergonomic it will end up.
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