If matching root doc's inner objects don't match the nested_filter …

…then the `missing` value should be used to sort the root doc.

Closes elastic#3020

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/ByteValuesComparator.java

@@ -66,4 +66,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = (byte) missingValue;
+    }
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/DoubleValuesComparator.java

@@ -66,4 +66,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = missingValue;
+    }
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/DoubleValuesComparatorBase.java

@@ -61,6 +61,11 @@ public final FieldComparator<T> setNextReader(AtomicReaderContext context) throw
         return this;
     }
 
+    @Override
+    public int compareBottomMissing() {
+        return compare(bottom, missingValue);
+    }
+
     static final int compare(double left, double right) {
         return Double.compare(left, right);
     }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/FloatValuesComparator.java

@@ -66,4 +66,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = (float) missingValue;
+    }
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/IntValuesComparator.java

@@ -72,4 +72,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = (int) missingValue;
+    }
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/LongValuesComparator.java

@@ -65,4 +65,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = missingValue;
+    }
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/LongValuesComparatorBase.java

@@ -72,6 +72,11 @@ public final FieldComparator<T> setNextReader(AtomicReaderContext context) throw
         return this;
     }
 
+    @Override
+    public int compareBottomMissing() {
+        return compare(bottom, missingValue);
+    }
+
     private static final class MultiValueWrapper extends LongValues.Filtered {
 
         private final SortMode sortMode;

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/NumberComparatorBase.java

@@ -42,4 +42,19 @@ public abstract class NumberComparatorBase<T> extends FieldComparator<T> {
      * @param divisor   The specified divisor
      */
     public abstract void divide(int slot, int divisor);
+
+    /**
+     * Assigns the underlying missing value to the specified slot, if the actual implementation supports missing value.
+     *
+     * @param slot The slot to assign the the missing value to.
+     */
+    public abstract void missing(int slot);
+
+    /**
+     * Compares the missing value to the bottom.
+     *
+     * @return any N < 0 if the bottom value is not competitive with the missing value, any N > 0 if the
+     * bottom value is competitive with the missing value and 0 if they are equal.
+     */
+    public abstract int compareBottomMissing();
 }

src/main/java/org/elasticsearch/index/fielddata/fieldcomparator/ShortValuesComparator.java

@@ -68,4 +68,9 @@ public void add(int slot, int doc) {
     public void divide(int slot, int divisor) {
         values[slot] /= divisor;
     }
+
+    @Override
+    public void missing(int slot) {
+        values[slot] = (short) missingValue;
+    }
 }