etseidl commented on code in PR #197:
URL: https://github.com/apache/parquet-format/pull/197#discussion_r1302095236
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src/main/thrift/parquet.thrift:
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@@ -974,6 +1050,13 @@ struct ColumnIndex {
/** A list containing the number of null values for each page **/
5: optional list<i64> null_counts
+ /**
+ * Repetition and definition level histograms for the pages.
+ *
+ * This contains some redundancy with null_counts, however, to accommodate
the
+ * widest range of readers both should be populated.
+ **/
+ 6: optional list<RepetitionDefinitionLevelHistogram>
repetition_definition_level_histograms;
Review Comment:
> I think `SizeEstimationStatistics` is already in `ColumnChunk`, would a
page level `unencoded_variable_width_stored_bytes` helps pruning? Since here
the `repetition_definition_level_histograms` can help pruning like
`struct.list_child == null`?
My use case for the information isn't necessarily pruning (in the filtering
sense), but to figure out how large of a batch I can read from a set of files
and still remain within a memory budget.
> If we want this it's even more better to put
`unencoded_variable_width_stored_bytes` into `OffsetIndex`. It's much more like
`compressed_page_size` there.
This would be ideal...it's what I originally wanted to propose.
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