gszadovszky commented on code in PR #196:
URL: https://github.com/apache/parquet-format/pull/196#discussion_r1243891389
##########
src/main/thrift/parquet.thrift:
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@@ -966,6 +985,23 @@ struct ColumnIndex {
/** A list containing the number of null values for each page **/
5: optional list<i64> null_counts
+
+ /**
+ * A list of Boolean values to determine pages that contain only NaNs. Only
+ * present for columns of type FLOAT and DOUBLE. If true, all non-null
+ * values in a page are NaN. Writers are suggested to set the corresponding
+ * entries in min_values and max_values to NaN, so that all lists have the
same
+ * length and contain valid values. If false, then either all values in the
+ * page are null or there is at least one non-null non-NaN value in the page.
+ * As readers are supposed to ignore all NaN values in bounds, legacy readers
+ * who do not consider nan_pages yet are still able to use the column index
+ * but are not able to skip only-NaN pages.
+ */
+ 6: optional list<bool> nan_pages
Review Comment:
@pitrou, sorry `BoundaryOrder` was a mistype. I was talking about
[ColumnOrder](https://github.com/apache/parquet-format/blob/master/src/main/thrift/parquet.thrift#L863).
The only order we have currently is `TypeDefinedOrder` that is specified. We
were thinking about adding a `ColumnOrder` for FLOAT/DOUBLE with the definition
of a total ordering that includes NaN values, -0.0,
and +0.0 values.
Maybe you're right that the in case of the default string ordering is not
enough to a system it shall write its own indices. But there was an idea behind
ColumnOrder to maybe implement collations to support those systems.
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