DRILL-7187: Improve selectivity estimation of BETWEEN predicates and arbitrary combination of range predicates.

Address review comments.

Modify unit test expected rowcount after rebasing.

close #1772

Author: Aman Sinha

exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/DrillStatsTable.java

@@ -120,7 +120,7 @@ public Double getNdv(SchemaPath col) {
     Long ndvCol = ndv.get(col);
     // Ndv estimation techniques like HLL may over-estimate, hence cap it at rowCount
     if (ndvCol != null) {
-      return Math.min(ndvCol, rowCount);
+      return (double) Math.min(ndvCol, rowCount);
     }
     return null;
   }
@@ -185,7 +185,6 @@ public Histogram getHistogram(SchemaPath column) {
     return histogram.get(column);
   }
 
-
   /**
    * Read the stats from storage and keep them in memory.
    */
@@ -337,7 +336,7 @@ public void setType(TypeProtos.MajorType type) {
       this.type = type;
     }
     @JsonGetter ("schema")
-    public double getSchema() {
+    public long getSchema() {
       return this.schema;
     }
     @JsonSetter ("schema")
@@ -494,6 +493,10 @@ public static Map<StatisticsKind, Object> getEstimatedColumnStats(DrillStatsTabl
       if (histogram != null) {
         statisticsValues.put(ColumnStatisticsKind.HISTOGRAM, histogram);
       }
+      Double rowcount = statsProvider.getRowCount();
+      if (rowcount != null) {
+        statisticsValues.put(ColumnStatisticsKind.ROWCOUNT, rowcount);
+      }
       return statisticsValues;
     }
     return Collections.emptyMap();

exec/java-exec/src/main/java/org/apache/drill/exec/planner/common/Histogram.java

@@ -35,7 +35,8 @@ public interface Histogram {
   /**
    * For a filter condition, estimate the selectivity (matching rows/total rows) for this histogram
    * @param filter
+   * @param totalRowCount
    * @return estimated selectivity or NULL if it could not be estimated for any reason
    */
-  Double estimatedSelectivity(final RexNode filter);
+  Double estimatedSelectivity(final RexNode filter, final long totalRowCount);
 }