Use AggregateDataCollecting for MEDIAN aggregate

h2/src/main/org/h2/expression/aggregate/Aggregate.java

@@ -402,7 +402,7 @@ public class Aggregate extends AbstractAggregate {
             return v;
         }
         case MEDIAN:
-            return AggregateDataMedian.getResultFromIndex(session, on, dataType);
+            return AggregateMedian.medianFromIndex(session, on, dataType);
         case ENVELOPE:
             return ((MVSpatialIndex) AggregateDataEnvelope.getGeometryColumnIndex(on)).getBounds(session);
         default:
@@ -459,6 +459,13 @@ public class Aggregate extends AbstractAggregate {
             }
             return ValueArray.get(array);
         }
+        case MEDIAN: {
+            Value[] array = ((AggregateDataCollecting) data).getArray();
+            if (array == null) {
+                return ValueNull.INSTANCE;
+            }
+            return AggregateMedian.median(session.getDatabase(), array, dataType);
+        }
         case MODE:
             if (orderByList != null) {
                 return ((AggregateDataMode) data).getOrderedValue(session.getDatabase(), dataType,
@@ -762,7 +769,7 @@ public class Aggregate extends AbstractAggregate {
                 if (distinct) {
                     return false;
                 }
-                return AggregateDataMedian.getMedianColumnIndex(on) != null;
+                return AggregateMedian.getMedianColumnIndex(on) != null;
             case ENVELOPE:
                 return AggregateDataEnvelope.getGeometryColumnIndex(on) != null;
             default:

h2/src/main/org/h2/expression/aggregate/AggregateData.java

@@ -26,6 +26,7 @@ abstract class AggregateData {
             return new AggregateDataSelectivity();
         case GROUP_CONCAT:
         case ARRAY_AGG:
+        case MEDIAN:
             return new AggregateDataCollecting();
         case COUNT_ALL:
             return new AggregateDataCountAll();
@@ -33,8 +34,6 @@ abstract class AggregateData {
             return new AggregateDataCount();
         case HISTOGRAM:
             return new AggregateDataHistogram();
-        case MEDIAN:
-            return new AggregateDataMedian();
         case MODE:
             return new AggregateDataMode();
         case ENVELOPE:

h2/src/main/org/h2/expression/aggregate/AggregateDataCollecting.java

@@ -20,8 +20,7 @@ import org.h2.value.ValueNull;
  * <p>
  * NULL values are not collected. {@link #getValue(Database, int, boolean)}
  * method returns {@code null}. Use {@link #getArray()} for instances of this
- * class instead. Notice that subclasses like {@link AggregateDataMedian} may
- * override {@link #getValue(Database, int, boolean)} to return useful result.
+ * class instead.
  * </p>
  */
 class AggregateDataCollecting extends AggregateData {

h2/src/main/org/h2/expression/aggregate/AggregateDataMedian.java → h2/src/main/org/h2/expression/aggregate/AggregateMedian.java

@@ -41,9 +41,10 @@ import org.h2.value.ValueTimestamp;
 import org.h2.value.ValueTimestampTimeZone;
 
 /**
- * Data stored while calculating a MEDIAN aggregate.
+ * MEDIAN aggregate.
  */
-class AggregateDataMedian extends AggregateDataCollecting {
+final class AggregateMedian {
+
     private static boolean isNullsLast(Index index) {
         IndexColumn ic = index.getIndexColumns()[0];
         int sortType = ic.sortType;
@@ -91,14 +92,34 @@ class AggregateDataMedian extends AggregateDataCollecting {
     }
 
     /**
-     * Get the result from the index.
+     * Get the median from the array of values.
+     *
+     * @param database the database
+     * @param array array with values
+     * @param dataType the data type
+     * @return the result
+     */
+    static Value median(Database database, Value[] array, int dataType) {
+        final CompareMode compareMode = database.getCompareMode();
+        Arrays.sort(array, compareMode);
+        int len = array.length;
+        int idx = len / 2;
+        Value v1 = array[idx];
+        if ((len & 1) == 1) {
+            return v1.convertTo(dataType);
+        }
+        return getMedian(array[idx - 1], v1, dataType, database.getMode(), compareMode);
+    }
+
+    /**
+     * Get the median from the index.
      *
      * @param session the session
      * @param on the expression
      * @param dataType the data type
      * @return the result
      */
-    static Value getResultFromIndex(Session session, Expression on, int dataType) {
+    static Value medianFromIndex(Session session, Expression on, int dataType) {
         Index index = getMedianColumnIndex(on);
         long count = index.getRowCount(session);
         if (count == 0) {
@@ -172,25 +193,9 @@ class AggregateDataMedian extends AggregateDataCollecting {
         return v;
     }
 
-    @Override
-    Value getValue(Database database, int dataType, boolean distinct) {
-        Value[] a = getArray();
-        if (a == null) {
-            return ValueNull.INSTANCE;
-        }
-        final CompareMode compareMode = database.getCompareMode();
-        Arrays.sort(a, compareMode);
-        int len = a.length;
-        int idx = len / 2;
-        Value v1 = a[idx];
-        if ((len & 1) == 1) {
-            return v1.convertTo(dataType);
-        }
-        return getMedian(a[idx - 1], v1, dataType, database.getMode(), compareMode);
-    }
-
     private static Value getMedian(Value v0, Value v1, int dataType, Mode databaseMode, CompareMode compareMode) {
-        if (v0.compareTo(v1, databaseMode, compareMode) == 0) {
+        int cmp = v0.compareTo(v1, databaseMode, compareMode);
+        if (cmp == 0) {
             return v0.convertTo(dataType);
         }
         switch (dataType) {
@@ -268,9 +273,12 @@ class AggregateDataMedian extends AggregateDataCollecting {
                     IntervalUtils.intervalToAbsolute((ValueInterval) v0)
                             .add(IntervalUtils.intervalToAbsolute((ValueInterval) v1)).shiftRight(1));
         default:
-            // Just return first
-            return v0.convertTo(dataType);
+            // Just return smaller
+            return (cmp < 0 ? v0 : v1).convertTo(dataType);
+        }
     }
+
+    private AggregateMedian() {
     }
 
 }