mapleFU commented on code in PR #196:
URL: https://github.com/apache/parquet-format/pull/196#discussion_r1146114852
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README.md:
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@@ -163,18 +163,25 @@ following rules:
[Thrift definition](src/main/thrift/parquet.thrift) in the
`ColumnOrder` union. They are summarized here but the Thrift definition
is considered authoritative:
- * NaNs should not be written to min or max statistics fields.
- * If the computed max value is zero (whether negative or positive),
- `+0.0` should be written into the max statistics field.
- * If the computed min value is zero (whether negative or positive),
- `-0.0` should be written into the min statistics field.
-
- For backwards compatibility when reading files:
- * If the min is a NaN, it should be ignored.
- * If the max is a NaN, it should be ignored.
- * If the min is +0, the row group may contain -0 values as well.
- * If the max is -0, the row group may contain +0 values as well.
- * When looking for NaN values, min and max should be ignored.
+ * The following compatibility rules should be applied when reading
statistics:
+ * If the nan_count field is set to > 0 and both min and max are
Review Comment:
I got it, I think using both min-max is backward-capatible and can represent
"all-data-is-nan".
https://github.com/apache/parquet-format/blob/master/src/main/thrift/parquet.thrift#L944
can we import a status like that?
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