mapleFU commented on code in PR #8098:
URL: https://github.com/apache/arrow-rs/pull/8098#discussion_r2278260927
##########
parquet/src/file/properties.rs:
##########
@@ -1155,6 +1177,11 @@ impl ColumnProperties {
fn bloom_filter_properties(&self) -> Option<&BloomFilterProperties> {
self.bloom_filter_properties.as_ref()
}
+
+ /// Returns the statistics truncate length for this column.
+ fn statistics_truncate_length(&self) -> Option<Option<usize>> {
Review Comment:
> Why is this an `Option<Option<size>>`?
This is from the style of `ColumnProperties` api:
1. The api is defined as:
https://github.com/apache/arrow-rs/blob/48b723f118740dd6d8aa82249ffa975efa51200d/parquet/src/file/properties.rs#L1029-L1038
. `Optional` here means "whether the value is defined"
2. the caller side uses the code below:
https://github.com/apache/arrow-rs/blob/48b723f118740dd6d8aa82249ffa975efa51200d/parquet/src/file/properties.rs#L379-L385
Here it uses an `Option` to determine whether the value is defined. If
column and default column doesn't define this value, it would be `Option`.
And the `Option::None` truncate means "do not truncate". So here the first
layer means "defined", the second layer means whether to truncate the values
##########
parquet/src/file/properties.rs:
##########
@@ -1155,6 +1177,11 @@ impl ColumnProperties {
fn bloom_filter_properties(&self) -> Option<&BloomFilterProperties> {
self.bloom_filter_properties.as_ref()
}
+
+ /// Returns the statistics truncate length for this column.
+ fn statistics_truncate_length(&self) -> Option<Option<usize>> {
Review Comment:
I'll document it here
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