[GitHub] vrozov commented on a change in pull request #1406: DRILL-6641: Fix columnValueCounts in ParquetGroupScanStatistics when ParquetGroupScan has RowGroupInfo without column statistics

[GitBox <gi...@apache.org>]

vrozov commented on a change in pull request #1406: DRILL-6641: Fix columnValueCounts in ParquetGroupScanStatistics when ParquetGroupScan has RowGroupInfo without column statistics
URL: https://github.com/apache/drill/pull/1406#discussion_r205825339
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/ParquetGroupScanStatistics.java
 ##########
 @@ -88,19 +88,14 @@ public void collect(List<RowGroupInfo> rowGroupInfos, ParquetTableMetadataBase p
       for (ColumnMetadata column : rowGroup.getColumns()) {
         SchemaPath schemaPath = SchemaPath.getCompoundPath(column.getName());
         Long previousCount = columnValueCounts.get(schemaPath);
-        if (previousCount != null) {
-          if (previousCount != GroupScan.NO_COLUMN_STATS && column.isNumNullsSet()) {
-            Long newCount = rowCount - column.getNulls();
-            columnValueCounts.put(schemaPath, columnValueCounts.get(schemaPath) + newCount);
-          }
+        previousCount = previousCount == null ? 0 : previousCount;
 
 Review comment:
   Unnecessary boxing/unboxing and hash lookups. Consider
   ```
           long newCount = GroupScan.NO_COLUMN_STATS;
           if (column.isNumNullsSet()) {
             newCount = rowCount - column.getNulls();
             Long previousCount = columnValueCounts.get(schemaPath);
             if (previousCount != null) {
               if (GroupScan.NO_COLUMN_STATS != previousCount) {
                 newCount += previousCount;
               } else {
                 continue;
               }
             }
           }
           columnValueCounts.put(schemaPath, newCount);
   ```

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