Move getPointReaderOrNull into AggregatorBase

server/src/main/java/org/elasticsearch/index/mapper/DateFieldMapper.java

@@ -64,6 +64,7 @@
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
+import java.util.function.Function;
 import java.util.function.LongSupplier;
 
 import static org.elasticsearch.common.time.DateUtils.toLong;
@@ -490,6 +491,14 @@ public Relation isFieldWithinQuery(IndexReader reader,
             }
         }
 
+        @Override
+        public Function<byte[], Number> pointReaderIfPossible() {
+            if (isSearchable()) {
+                return resolution()::parsePointAsMillis;
+            }
+            return null;
+        }
+
         @Override
         public IndexFieldData.Builder fielddataBuilder(String fullyQualifiedIndexName) {
             failIfNoDocValues();

server/src/main/java/org/elasticsearch/index/mapper/MappedFieldType.java

@@ -53,6 +53,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.function.Function;
 
 /**
  * This defines the core properties and functions to operate on a field.
@@ -129,7 +130,7 @@ public int hashCode() {
 
     /** Returns the name of this type, as would be specified in mapping properties */
     public abstract String typeName();
-    
+
     /** Returns the field family type, as used in field capabilities */
     public String familyTypeName() {
         return typeName();
@@ -173,6 +174,17 @@ public boolean isSearchable() {
         return isIndexed;
     }
 
+    /**
+     * If the field supports using the indexed data to speed up operations related to ordering of data, such as sorting or aggs, return
+     * a function for doing that.  If it is unsupported for this field type, there is no need to override this method.
+     *
+     * @return null if the optimization cannot be applied, otherwise a function to use for the optimization
+     */
+    @Nullable
+    public Function<byte[], Number> pointReaderIfPossible() {
+        return null;
+    }
+
     /** Returns true if the field is aggregatable.
      *
      */

server/src/main/java/org/elasticsearch/index/mapper/NumberFieldMapper.java

@@ -66,6 +66,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.function.Function;
 
 /** A {@link FieldMapper} for numeric types: byte, short, int, long, float and double. */
 public class NumberFieldMapper extends FieldMapper {
@@ -971,6 +972,14 @@ public Query rangeQuery(Object lowerTerm, Object upperTerm, boolean includeLower
             return query;
         }
 
+        @Override
+        public Function<byte[], Number> pointReaderIfPossible() {
+            if (isSearchable()) {
+                return this::parsePoint;
+            }
+            return null;
+        }
+
         @Override
         public IndexFieldData.Builder fielddataBuilder(String fullyQualifiedIndexName) {
             failIfNoDocValues();

server/src/main/java/org/elasticsearch/search/aggregations/AggregatorBase.java

@@ -19,11 +19,13 @@
 package org.elasticsearch.search.aggregations;
 
 import org.apache.lucene.index.LeafReaderContext;
+import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.ScoreMode;
 import org.elasticsearch.common.breaker.CircuitBreaker;
 import org.elasticsearch.common.breaker.CircuitBreakingException;
 import org.elasticsearch.indices.breaker.CircuitBreakerService;
 import org.elasticsearch.search.SearchShardTarget;
+import org.elasticsearch.search.aggregations.support.ValuesSourceConfig;
 import org.elasticsearch.search.internal.SearchContext;
 import org.elasticsearch.search.internal.SearchContext.Lifetime;
 import org.elasticsearch.search.query.QueryPhaseExecutionException;
@@ -34,6 +36,7 @@
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 /**
  * Base implementation for concrete aggregators.
@@ -106,6 +109,26 @@ public ScoreMode scoreMode() {
         addRequestCircuitBreakerBytes(DEFAULT_WEIGHT);
     }
 
+    /**
+     * Returns a converter for point values if it's safe to use the indexed data instead of
+     * doc values.  Generally, this means that the query has no filters or scripts, the aggregation is
+     * top level, and the underlying field is indexed, and the index is sorted in the right order.
+     *
+     * If those conditions aren't met, return <code>null</code> to indicate a point reader cannot
+     * be used in this case.
+     *
+     * @param config The config for the values source metric.
+     */
+    public final Function<byte[], Number> pointReaderIfAvailable(ValuesSourceConfig config) {
+        if (context.query() != null && context.query().getClass() != MatchAllDocsQuery.class) {
+            return null;
+        }
+        if (parent != null) {
+            return null;
+        }
+        return config.getPointReaderOrNull();
+    }
+
     /**
      * Increment or decrement the number of bytes that have been allocated to service
      * this request and potentially trigger a {@link CircuitBreakingException}. The

server/src/main/java/org/elasticsearch/search/aggregations/metrics/MaxAggregator.java

@@ -44,8 +44,6 @@
 import java.util.Map;
 import java.util.function.Function;
 
-import static org.elasticsearch.search.aggregations.metrics.MinAggregator.getPointReaderOrNull;
-
 class MaxAggregator extends NumericMetricsAggregator.SingleValue {
 
     final ValuesSource.Numeric valuesSource;
@@ -68,7 +66,7 @@ class MaxAggregator extends NumericMetricsAggregator.SingleValue {
             maxes.fill(0, maxes.size(), Double.NEGATIVE_INFINITY);
         }
         this.formatter = config.format();
-        this.pointConverter = getPointReaderOrNull(context, parent, config);
+        this.pointConverter = pointReaderIfAvailable(config);
         if (pointConverter != null) {
             pointField = config.fieldContext().field();
         } else {
@@ -96,7 +94,7 @@ public LeafBucketCollector getLeafCollector(LeafReaderContext ctx,
             Number segMax = findLeafMaxValue(ctx.reader(), pointField, pointConverter);
             if (segMax != null) {
                 /*
-                 * There is no parent aggregator (see {@link MinAggregator#getPointReaderOrNull}
+                 * There is no parent aggregator (see {@link AggregatorBase#getPointReaderOrNull}
                  * so the ordinal for the bucket is always 0.
                  */
                 assert maxes.size() == 1;

server/src/main/java/org/elasticsearch/search/aggregations/metrics/MinAggregator.java

@@ -22,17 +22,13 @@
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.PointValues;
 import org.apache.lucene.search.CollectionTerminatedException;
-import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.ScoreMode;
 import org.apache.lucene.util.Bits;
 import org.elasticsearch.common.lease.Releasables;
 import org.elasticsearch.common.util.BigArrays;
 import org.elasticsearch.common.util.DoubleArray;
 import org.elasticsearch.index.fielddata.NumericDoubleValues;
 import org.elasticsearch.index.fielddata.SortedNumericDoubleValues;
-import org.elasticsearch.index.mapper.DateFieldMapper;
-import org.elasticsearch.index.mapper.MappedFieldType;
-import org.elasticsearch.index.mapper.NumberFieldMapper;
 import org.elasticsearch.search.DocValueFormat;
 import org.elasticsearch.search.MultiValueMode;
 import org.elasticsearch.search.aggregations.Aggregator;
@@ -71,7 +67,7 @@ class MinAggregator extends NumericMetricsAggregator.SingleValue {
             mins.fill(0, mins.size(), Double.POSITIVE_INFINITY);
         }
         this.format = config.format();
-        this.pointConverter = getPointReaderOrNull(context, parent, config);
+        this.pointConverter = pointReaderIfAvailable(config);
         if (pointConverter != null) {
             pointField = config.fieldContext().field();
         } else {
@@ -159,40 +155,6 @@ public void doClose() {
     }
 
 
-    /**
-     * Returns a converter for point values if early termination is applicable to
-     * the context or <code>null</code> otherwise.
-     *
-     * @param context The {@link SearchContext} of the aggregation.
-     * @param parent The parent aggregator.
-     * @param config The config for the values source metric.
-     */
-    static Function<byte[], Number> getPointReaderOrNull(SearchContext context, Aggregator parent,
-                                                                ValuesSourceConfig config) {
-        if (context.query() != null &&
-                context.query().getClass() != MatchAllDocsQuery.class) {
-            return null;
-        }
-        if (parent != null) {
-            return null;
-        }
-        if (config.fieldContext() != null && config.script() == null && config.missing() == null) {
-            MappedFieldType fieldType = config.fieldContext().fieldType();
-            if (fieldType == null || fieldType.isSearchable() == false) {
-                return null;
-            }
-            Function<byte[], Number> converter = null;
-            if (fieldType instanceof NumberFieldMapper.NumberFieldType) {
-                converter = ((NumberFieldMapper.NumberFieldType) fieldType)::parsePoint;
-            } else if (fieldType.getClass() == DateFieldMapper.DateFieldType.class) {
-                DateFieldMapper.DateFieldType dft = (DateFieldMapper.DateFieldType) fieldType;
-                converter = dft.resolution()::parsePointAsMillis;
-            }
-            return converter;
-        }
-        return null;
-    }
-
     /**
      * Returns the minimum value indexed in the <code>fieldName</code> field or <code>null</code>
      * if the value cannot be inferred from the indexed {@link PointValues}.

server/src/main/java/org/elasticsearch/search/aggregations/support/ValuesSourceConfig.java

@@ -30,6 +30,7 @@
 import org.elasticsearch.search.DocValueFormat;
 
 import java.time.ZoneId;
+import java.util.function.Function;
 import java.util.function.LongSupplier;
 
 /**
@@ -372,6 +373,23 @@ public boolean hasGlobalOrdinals() {
         return valuesSource.hasGlobalOrdinals();
     }
 
+    /**
+     * This method is used when an aggregation can optimize by using the indexed data instead of the doc values.  We check to see if the
+     * indexed data will match the values source output (meaning there isn't a script or a missing value, since both could modify the
+     * value at read time).  If the settings allow for it, we then ask the {@link ValuesSourceType} to build the actual point reader
+     * based on the field type.  This allows for a point of extensibility in plugins.
+     *
+     * @return null if we cannot apply the optimization, otherwise the point reader function.
+     */
+    @Nullable
+    public Function<byte[], Number> getPointReaderOrNull() {
+        MappedFieldType fieldType = fieldType();
+        if (fieldType != null && script() == null && missing() == null) {
+            return fieldType.pointReaderIfPossible();
+        }
+        return null;
+    }
+
     /**
      * Returns a human readable description of this values source, for use in error messages and similar.
      */