Address MinAndMax generics warnings

The MinAndMax encapsulates min and max values for a shard. It uses generics to make sure that the values are of the same type and are also comparable. Though there are warnings whenever this class is currently used, which are addressed with this commit.

Relates to elastic#49092

server/src/main/java/org/elasticsearch/action/search/CanMatchPreFilterSearchPhase.java

@@ -122,7 +122,7 @@ private static List<SearchShardIterator> sortShards(GroupShardsIterator<SearchSh
         return IntStream.range(0, shardsIts.size())
             .boxed()
             .sorted(shardComparator(shardsIts, minAndMaxes,  order))
-            .map(ord -> shardsIts.get(ord))
+            .map(shardsIts::get)
             .collect(Collectors.toList());
     }
 

server/src/main/java/org/elasticsearch/search/sort/FieldSortBuilder.java

@@ -434,7 +434,7 @@ public static FieldSortBuilder getPrimaryFieldSortOrNull(SearchSourceBuilder sou
      * {@link SortField}. This is needed for {@link SortField} that converts values from one type to another using
      * {@link FieldSortBuilder#setNumericType(String)} )} (e.g.: long to double).
      */
-    private static Function<byte[], Comparable> numericPointConverter(SortField sortField, NumberFieldType numberFieldType) {
+    private static Function<byte[], Comparable<?>> numericPointConverter(SortField sortField, NumberFieldType numberFieldType) {
         switch (IndexSortConfig.getSortFieldType(sortField)) {
             case LONG:
                 return v -> numberFieldType.parsePoint(v).longValue();
@@ -457,7 +457,7 @@ private static Function<byte[], Comparable> numericPointConverter(SortField sort
      * Return a {@link Function} that converts a serialized date point into a {@link Long} according to the provided
      * {@link NumericType}.
      */
-    private static Function<byte[], Comparable> datePointConverter(DateFieldType dateFieldType, String numericTypeStr) {
+    private static Function<byte[], Comparable<?>> datePointConverter(DateFieldType dateFieldType, String numericTypeStr) {
         if (numericTypeStr != null) {
             NumericType numericType = resolveNumericType(numericTypeStr);
             if (dateFieldType.resolution() == MILLISECONDS && numericType == NumericType.DATE_NANOSECONDS) {
@@ -491,7 +491,7 @@ public static MinAndMax<?> getMinMaxOrNull(QueryShardContext context, FieldSortB
             case INT:
             case DOUBLE:
             case FLOAT:
-                final Function<byte[], Comparable> converter;
+                final Function<byte[], Comparable<?>> converter;
                 if (fieldType instanceof NumberFieldType) {
                     converter = numericPointConverter(sortField, (NumberFieldType) fieldType);
                 } else if (fieldType instanceof DateFieldType) {
@@ -502,9 +502,7 @@ public static MinAndMax<?> getMinMaxOrNull(QueryShardContext context, FieldSortB
                 if (PointValues.size(reader, fieldName) == 0) {
                     return null;
                 }
-                final Comparable min = converter.apply(PointValues.getMinPackedValue(reader, fieldName));
-                final Comparable max = converter.apply(PointValues.getMaxPackedValue(reader, fieldName));
-                return MinAndMax.newMinMax(min, max);
+                return extractMinAndMax(reader, fieldName, converter);
 
             case STRING:
             case STRING_VAL:
@@ -520,6 +518,14 @@ public static MinAndMax<?> getMinMaxOrNull(QueryShardContext context, FieldSortB
         return null;
     }
 
+    @SuppressWarnings("unchecked")
+    private static <T extends Comparable<T>> MinAndMax<T> extractMinAndMax(IndexReader reader, String fieldName,
+                                                              Function<byte[], Comparable<?>> converter) throws IOException {
+        final T min = (T)converter.apply(PointValues.getMinPackedValue(reader, fieldName));
+        final T max = (T)converter.apply(PointValues.getMaxPackedValue(reader, fieldName));
+        return MinAndMax.newMinMax(min, max);
+    }
+
     /**
      * Throws an exception if max children is not located at top level nested sort.
      */
@@ -601,12 +607,12 @@ public static FieldSortBuilder fromXContent(XContentParser parser, String fieldN
     private static final ObjectParser<FieldSortBuilder, Void> PARSER = new ObjectParser<>(NAME);
 
     static {
-        PARSER.declareField(FieldSortBuilder::missing, p -> p.objectText(),  MISSING, ValueType.VALUE);
+        PARSER.declareField(FieldSortBuilder::missing, XContentParser::objectText,  MISSING, ValueType.VALUE);
         PARSER.declareString(FieldSortBuilder::unmappedType , UNMAPPED_TYPE);
         PARSER.declareString((b, v) -> b.order(SortOrder.fromString(v)) , ORDER_FIELD);
         PARSER.declareString((b, v) -> b.sortMode(SortMode.fromString(v)), SORT_MODE);
         PARSER.declareObject(FieldSortBuilder::setNestedSort, (p, c) -> NestedSortBuilder.fromXContent(p), NESTED_FIELD);
-        PARSER.declareString((b, v) -> b.setNumericType(v), NUMERIC_TYPE);
+        PARSER.declareString(FieldSortBuilder::setNumericType, NUMERIC_TYPE);
     }
 
     @Override

server/src/main/java/org/elasticsearch/search/sort/MinAndMax.java

@@ -29,9 +29,9 @@
 import java.util.Objects;
 
 /**
- * A class that encapsulates a minimum and a maximum {@link Comparable}.
+ * A class that encapsulates a minimum and a maximum, that are of the same type and {@link Comparable}.
  */
-public class MinAndMax<T extends Comparable<? super T>> implements Writeable {
+public class MinAndMax<T extends Comparable<T>> implements Writeable {
     private final T minValue;
     private final T maxValue;
 
@@ -40,9 +40,10 @@ private MinAndMax(T minValue, T maxValue) {
         this.maxValue = Objects.requireNonNull(maxValue);
     }
 
+    @SuppressWarnings("unchecked")
     public MinAndMax(StreamInput in) throws IOException {
-        this.minValue = (T) Lucene.readSortValue(in);
-        this.maxValue = (T) Lucene.readSortValue(in);
+        this.minValue = (T)Lucene.readSortValue(in);
+        this.maxValue = (T)Lucene.readSortValue(in);
     }
 
     @Override
@@ -54,27 +55,28 @@ public void writeTo(StreamOutput out) throws IOException {
     /**
      * Return the minimum value.
      */
-    public T getMin() {
+    T getMin() {
         return minValue;
     }
 
     /**
      * Return the maximum value.
      */
-    public T getMax() {
+    T getMax() {
         return maxValue;
     }
 
-    public static <T extends Comparable<? super T>> MinAndMax<T> newMinMax(T min, T max) {
+    public static <T extends Comparable<T>> MinAndMax<T> newMinMax(T min, T max) {
         return new MinAndMax<>(min, max);
     }
 
     /**
      * Return a {@link Comparator} for {@link MinAndMax} values according to the provided {@link SortOrder}.
      */
     public static Comparator<MinAndMax<?>> getComparator(SortOrder order) {
-        Comparator<MinAndMax> cmp = order == SortOrder.ASC  ?
-            Comparator.comparing(v -> (Comparable) v.getMin()) : Comparator.comparing(v -> (Comparable) v.getMax());
+        Comparator<MinAndMax<?>> cmp = order == SortOrder.ASC  ?
+            Comparator.comparing(MinAndMax::getMin) : Comparator.comparing(MinAndMax::getMax);
+
         if (order == SortOrder.DESC) {
             cmp = cmp.reversed();
         }