[GitHub] [arrow-rs] sunchao commented on a change in pull request #307: ensure null-counts are written for all-null columns

[GitBox]

sunchao commented on a change in pull request #307:
URL: https://github.com/apache/arrow-rs/pull/307#discussion_r635532034



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File path: parquet/src/column/writer.rs
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@@ -607,9 +607,11 @@ impl<T: DataType> ColumnWriterImpl<T> {
         let max_def_level = self.descr.max_def_level();
         let max_rep_level = self.descr.max_rep_level();
 
+        // always update column NULL count, no matter if page stats are used
+        self.num_column_nulls += self.num_page_nulls;

Review comment:
       hmm just curious why we don't need to update `self.num_page_nulls` 
accordingly, it is updated as follow:
   ```rust
               for &level in levels {
                   if level == self.descr.max_def_level() {
                       values_to_write += 1;
                   } else if calculate_page_stats {
                       self.num_page_nulls += 1
                   }
               }
   ```




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