zanmato1984 commented on code in PR #45822:
URL: https://github.com/apache/arrow/pull/45822#discussion_r2010336968
##########
cpp/src/arrow/compute/row/grouper.cc:
##########
@@ -649,11 +726,29 @@ struct GrouperFastImpl : public Grouper {
cols_[icol] = col_base.Slice(offset, num_rows);
}
+ std::shared_ptr<arrow::Buffer> group_ids, null_bitmap;
+ // If we need to return the group ids, then allocate a buffer of group ids
+ // for all rows, otherwise each minibatch will reuse the same buffer.
+ const int64_t groups_ids_size =
+ (mode == GrouperMode::kPopulate) ? minibatch_size_max_ : num_rows;
+ ARROW_ASSIGN_OR_RAISE(group_ids, AllocateBuffer(sizeof(uint32_t) *
groups_ids_size,
+ ctx_->memory_pool()));
+ if (mode == GrouperMode::kLookup) {
+ ARROW_ASSIGN_OR_RAISE(null_bitmap,
+ AllocateBitmap(groups_ids_size,
ctx_->memory_pool()));
+ }
+
// Split into smaller mini-batches
//
for (uint32_t start_row = 0; start_row < num_rows;) {
uint32_t batch_size_next =
std::min(static_cast<uint32_t>(minibatch_size_),
static_cast<uint32_t>(num_rows) -
start_row);
+ uint32_t* batch_group_ids = group_ids->mutable_data_as<uint32_t>() +
+ ((mode == GrouperMode::kPopulate) ? 0 :
start_row);
+ if (mode == GrouperMode::kLookup) {
+ // Zero-initialize
+ memset(batch_group_ids, 0, batch_size_next * sizeof(uint32_t));
+ }
Review Comment:
Indeed. Then maybe a short comment would help?
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