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Allow to get number of rows in record batch #39

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Merged
Avogar merged 1 commit into from
Aug 9, 2023
Merged

Allow to get number of rows in record batch #39

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17 changes: 17 additions & 0 deletions cpp/src/arrow/ipc/reader.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1240,6 +1240,23 @@ class RecordBatchFileReaderImpl : public RecordBatchFileReader {
return total;
}

Result<int64_t> RecordBatchCountRows(int i) override {
DCHECK_GE(i, 0);
DCHECK_LT(i, num_record_batches());
ARROW_ASSIGN_OR_RAISE(auto outer_message,
ReadMessageFromBlock(GetRecordBatchBlock(i)));
auto metadata = outer_message->metadata();
const flatbuf::Message* message = nullptr;
RETURN_NOT_OK(
internal::VerifyMessage(metadata->data(), metadata->size(), &message));
auto batch = message->header_as_RecordBatch();
if (batch == nullptr) {
return Status::IOError(
"Header-type of flatbuffer-encoded Message is not RecordBatch.");
}
return batch->length();
}

Status Open(const std::shared_ptr<io::RandomAccessFile>& file, int64_t footer_offset,
const IpcReadOptions& options) {
owned_file_ = file;
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2 changes: 2 additions & 0 deletions cpp/src/arrow/ipc/reader.h
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Expand Up @@ -203,6 +203,8 @@ class ARROW_EXPORT RecordBatchFileReader
/// \brief Computes the total number of rows in the file.
virtual Result<int64_t> CountRows() = 0;

virtual Result<int64_t> RecordBatchCountRows(int i) = 0;

/// \brief Begin loading metadata for the desired batches into memory.
///
/// This method will also begin loading all dictionaries messages into memory.
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