gszadovszky commented on code in PR #197:
URL: https://github.com/apache/parquet-format/pull/197#discussion_r1319479960
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src/main/thrift/parquet.thrift:
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@@ -977,6 +1073,15 @@ 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 when either the max
+ * definition and repetition level meet the requirements specified in
+ * RepetitionDefinitionLevelHistogram.
+ **/
+ 6: optional list<RepetitionDefinitionLevelHistogram>
repetition_definition_level_histograms
Review Comment:
@emkornfield
> @gszadovszky was item one a consideration in the original index design
(e.g. why wasn't a list of structs used?), it would be good to be consistent
with the original philosophy here.
I was not in the community at the design phase and could not find any docs
that mention this aspect. But since the whole design and a PoC was coming from
Impala I doubt if they would not consider and actually benchmark the different
aspects of the potential representations. What I do remember was about Thrift
structure vs. data page-like encoding (to save space) and the winner was the
Thrift structure because it was faster to read.
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