mapleFU commented on code in PR #197:
URL: https://github.com/apache/parquet-format/pull/197#discussion_r1302013630
##########
src/main/thrift/parquet.thrift:
##########
@@ -191,6 +191,64 @@ enum FieldRepetitionType {
REPEATED = 2;
}
+/**
+ * A histogram of repetition and definition levels for either a page or
column chunk.
+ *
+ * This is useful for:
+ * 1. Estimating the size of the data when materialized in memory
+ * 2. For filter push-down on nulls at various levels of nested structures
and
+ * list lengths.
+ */
+struct RepetitionDefinitionLevelHistogram {
+ /**
+ * When present, there is expected to be one element corresponding
+ to each repetition (i.e. size=max repetition_level+1)
Review Comment:
```suggestion
* to each repetition (i.e. size=max repetition_level+1)
```
##########
src/main/thrift/parquet.thrift:
##########
@@ -191,6 +191,64 @@ enum FieldRepetitionType {
REPEATED = 2;
}
+/**
+ * A histogram of repetition and definition levels for either a page or
column chunk.
+ *
+ * This is useful for:
+ * 1. Estimating the size of the data when materialized in memory
Review Comment:
(2) can be easily done with these statistics, but I wonder how can we
estimate the size of data with rep-def histogram...Is there any formulas?
##########
src/main/thrift/parquet.thrift:
##########
@@ -974,6 +1052,13 @@ 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
Review Comment:
```suggestion
* This contains some redundancy with null_counts, however, to
accommodate the
```
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