[GitHub] [drill] amansinha100 commented on a change in pull request #1728: DRILL-7089: Implement caching for TableMetadataProvider at query level and adapt statistics to use Drill metastore API

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amansinha100 commented on a change in pull request #1728: DRILL-7089: Implement caching for TableMetadataProvider at query level and adapt statistics to use Drill metastore API
URL: https://github.com/apache/drill/pull/1728#discussion_r272845354
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/metastore/ColumnStatisticsKind.java
 ##########
 @@ -106,6 +107,53 @@ public boolean isValueStatistic() {
     public boolean isExact() {
       return true;
     }
+  },
+
+  /**
+   * Column statistics kind which represents number of non-null values for the specific column.
+   */
+  NON_NULL_COUNT(Statistic.NNROWCOUNT) {
+    @Override
+    public Double mergeStatistics(List<? extends ColumnStatistics> statisticsList) {
+      double nonNullRowCount = 0;
+      for (ColumnStatistics statistics : statisticsList) {
+        Double nnRowCount = (Double) statistics.getStatistic(this);
+        if (nnRowCount != null) {
+          nonNullRowCount += nnRowCount;
+        }
+      }
+      return nonNullRowCount;
+    }
+  },
+
+  /**
+   * Column statistics kind which represents number of distinct values for the specific column.
+   */
+  NVD(Statistic.NDV) {
+    @Override
+    public Object mergeStatistics(List<? extends ColumnStatistics> statisticsList) {
+      throw new UnsupportedOperationException("Cannot merge statistics for NDV");
+    }
+  },
+
+  /**
+   * Column statistics kind which width of the specific column.
+   */
+  AVG_WIDTH(Statistic.AVG_WIDTH) {
+    @Override
+    public Object mergeStatistics(List<? extends ColumnStatistics> statisticsList) {
+      throw new UnsupportedOperationException("Cannot merge statistics for avg_width");
+    }
+  },
+
+  /**
+   * Column statistics kind which width of the specific column.
+   */
+  HISTOGRAM("histogram") {
+    @Override
+    public Object mergeStatistics(List<? extends ColumnStatistics> statisticsList) {
+      throw new UnsupportedOperationException("Cannot merge statistics for avg_width");
 
 Review comment:
   'statistics for histogram'

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