mapleFU commented on code in PR #43763:
URL: https://github.com/apache/arrow/pull/43763#discussion_r1739641829
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cpp/src/arrow/compute/row/row_encoder_internal.h:
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@@ -270,14 +348,26 @@ class ARROW_EXPORT RowEncoder {
}
int32_t num_rows() const {
- return offsets_.size() == 0 ? 0 : static_cast<int32_t>(offsets_.size() -
1);
+ return offsets_.empty() ? 0 : static_cast<int32_t>(offsets_.size() - 1);
}
private:
ExecContext* ctx_{nullptr};
std::vector<std::shared_ptr<KeyEncoder>> encoders_;
+ // offsets_ vector stores the starting position (offset) of each encoded row
+ // within the bytes_ vector. This allows for quick access to individual rows.
+ //
+ // The size would be num_rows + 1 if not empty, the last element is the total
+ // length of the bytes_ vector.
Review Comment:
Unrelated to this issue: I'm thinking of an optimization here. We can define
a flag to indicate that all the columns are fixed-sized or null. If it's, we
can not maintain the offsets, just static compute a `fixed-row-size`, and using
fixed-row-size to seek for the row.
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