Light-City commented on code in PR #37896:
URL: https://github.com/apache/arrow/pull/37896#discussion_r1358097865
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cpp/src/arrow/record_batch.cc:
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@@ -432,4 +433,43 @@ RecordBatchReader::~RecordBatchReader() {
ARROW_WARN_NOT_OK(this->Close(), "Implicitly called RecordBatchReader::Close
failed");
}
+Result<std::shared_ptr<RecordBatch>> ConcatenateRecordBatches(
+ const RecordBatchVector& batches, MemoryPool* pool) {
+ int64_t length = 0;
+ size_t n = batches.size();
+ if (n == 0) {
+ return Status::Invalid("Must pass at least one recordbatch");
+ }
+ if (n == 1) {
+ return batches[0];
+ }
+ int cols = batches[0]->num_columns();
+ auto schema = batches[0]->schema();
+ std::vector<std::shared_ptr<Array>> columns;
+ if (cols == 0) {
+ // special case: null batch, no data, just length
+ for (size_t i = 0; i < batches.size(); ++i) {
+ length += batches[i]->num_rows();
+ }
+ } else {
Review Comment:
The code looks very refreshing, but it does not handle the case of cols = 0.
In this case, cols = 0, length is not obtained.
For a batch, there may be cols = 0, the schema is empty, but there is
length. This kind of batch is used to process count(*) and does not store the
actual columns, only the number of rows.
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