Re: [PR] [Parquet] Minor: Update comments in page decompressor [arrow-rs]

["mapleFU (via GitHub)" <gi...@apache.org>]

mapleFU commented on code in PR #8764:
URL: https://github.com/apache/arrow-rs/pull/8764#discussion_r2488385460


##########
parquet/src/file/serialized_reader.rs:
##########
@@ -398,6 +396,8 @@ pub(crate) fn decode_page(
             let decompressed_size = uncompressed_page_size - offset;
             let mut decompressed = Vec::with_capacity(uncompressed_page_size);
             decompressed.extend_from_slice(&buffer[..offset]);
+            // decompressed size of zero corresponds to a page with only null values
+            // see https://github.com/apache/parquet-format/blob/master/README.md#data-pages

Review Comment:
   > I think the current wording is correct. In this case num_values is non-zero, so there are values, but they all just happen to be null (and thus are not encoded in the data).
   
   I mean, I don't know would a case that just `num_rows` ( not `num_values` ) == 0 would exists
   



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