mapleFU commented on code in PR #43763:
URL: https://github.com/apache/arrow/pull/43763#discussion_r1739596248
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cpp/src/arrow/compute/row/row_encoder_internal.h:
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@@ -250,6 +263,51 @@ struct ARROW_EXPORT NullKeyEncoder : KeyEncoder {
}
};
+/// RowEncoder encodes ExecSpan to a variable length byte sequence
+/// created by concatenating the encoded form of each column. The encoding
+/// for each column depends on its data type.
+///
+/// This is used to encode columns into row-major format, which will be
beneficial for grouping and joining operations.
+///
+/// Unlike DuckDB and arrow-rs, currently this row format can not help
+/// sortings because the row-format is uncomparable.
+///
+/// The row format is composed of the the KeyColumn encodings for each,
+/// and the column is encoded as follows:
+/// 1. A null byte for each column, indicating whether the column is null.
+/// "1" for null, "0" for non-null.
+/// 2. The "fixed width" encoding for the column, it would exists whether
+/// the column is null or not.
+/// 3. The "variable width" encoding for the column, it would exists only
+/// for non-null string/binary columns.
Review Comment:
change to variable payload
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