mapleFU commented on code in PR #35989:
URL: https://github.com/apache/arrow/pull/35989#discussion_r1252200622
##########
cpp/src/parquet/statistics.cc:
##########
@@ -552,12 +556,17 @@ class TypedStatisticsImpl : public TypedStatistics<DType>
{
void Merge(const TypedStatistics<DType>& other) override {
this->num_values_ += other.num_values();
+ // Merge always runs when Merge builder's page statistics
+ // into column chunk statistics, so it usually has null count.
Review Comment:
I know what you mean. This is a bit confusing:
1. `IncrementNullCount` will set `has_null_count_` to true ( but I think
it's not neccessary ). The `page_statistics_` would call `IncrementNullCount`
to set it( although at the first time `has_null_count_` would be true for it
2. `chunk_statistics_` will only call `merge`, once it meets a `Statistics`
without `has_null_count_`, it's `has_null_count_` would never be true.
##########
cpp/src/parquet/statistics.cc:
##########
@@ -552,12 +556,17 @@ class TypedStatisticsImpl : public TypedStatistics<DType>
{
void Merge(const TypedStatistics<DType>& other) override {
this->num_values_ += other.num_values();
+ // Merge always runs when Merge builder's page statistics
+ // into column chunk statistics, so it usually has null count.
Review Comment:
I know what you mean. This is a bit confusing:
1. `IncrementNullCount` will set `has_null_count_` to true ( but I think
it's not neccessary ). The `page_statistics_` would call `IncrementNullCount`
to set it( although at the first time `has_null_count_` would be true for it)
2. `chunk_statistics_` will only call `merge`, once it meets a `Statistics`
without `has_null_count_`, it's `has_null_count_` would never be true.
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