From 9805b8359b408e5bde4e0507646b09c6c17515e0 Mon Sep 17 00:00:00 2001
From: Colin Goodheart-Smithe <colin.goodheart-smithe@elasticsearch.com>
Date: Thu, 12 Feb 2015 15:47:06 +0000
Subject: [PATCH] can now reference single value metrics directly instead of
 having to add '.value' to the path

---
 .../reducers/derivative/DerivativeReducer.java | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/elasticsearch/search/aggregations/reducers/derivative/DerivativeReducer.java b/src/main/java/org/elasticsearch/search/aggregations/reducers/derivative/DerivativeReducer.java
index 76d3bd9b3ac..9a707687cc2 100644
--- a/src/main/java/org/elasticsearch/search/aggregations/reducers/derivative/DerivativeReducer.java
+++ b/src/main/java/org/elasticsearch/search/aggregations/reducers/derivative/DerivativeReducer.java
@@ -25,12 +25,14 @@ import com.google.common.collect.Lists;
 import org.elasticsearch.common.io.stream.StreamInput;
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.search.aggregations.Aggregation;
+import org.elasticsearch.search.aggregations.AggregationExecutionException;
 import org.elasticsearch.search.aggregations.Aggregator;
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.InternalAggregation.ReduceContext;
 import org.elasticsearch.search.aggregations.InternalAggregation.Type;
 import org.elasticsearch.search.aggregations.InternalAggregations;
 import org.elasticsearch.search.aggregations.bucket.histogram.InternalHistogram;
+import org.elasticsearch.search.aggregations.metrics.InternalNumericMetricsAggregation;
 import org.elasticsearch.search.aggregations.reducers.InternalSimpleValue;
 import org.elasticsearch.search.aggregations.reducers.Reducer;
 import org.elasticsearch.search.aggregations.reducers.ReducerFactory;
@@ -90,8 +92,7 @@ public class DerivativeReducer extends Reducer {
         Double lastBucketValue = null;
         // NOCOMMIT this needs to be improved so that the aggs are cloned correctly to ensure aggs are fully immutable.
         for (InternalHistogram.Bucket bucket : buckets) {
-            double thisBucketValue = (double) bucket.getProperty(histo.getName(), AggregationPath.parse(bucketsPath)
-                    .getPathElementsAsStringList());
+            double thisBucketValue = resolveBucketValue(histo, bucket);
             if (lastBucketValue != null) {
                 double diff = thisBucketValue - lastBucketValue;
 
@@ -109,6 +110,19 @@ public class DerivativeReducer extends Reducer {
         return factory.create(histo.getName(), newBuckets, null, 1, null, null, false, new ArrayList<Reducer>(), histo.getMetaData()); // NOCOMMIT get order, minDocCount, emptyBucketInfo etc. from histo
     }
 
+    private double resolveBucketValue(InternalHistogram<? extends InternalHistogram.Bucket> histo, InternalHistogram.Bucket bucket) {
+        Object propertyValue = bucket.getProperty(histo.getName(), AggregationPath.parse(bucketsPath)
+                .getPathElementsAsStringList());
+        if (propertyValue instanceof Number) {
+            return ((Number) propertyValue).doubleValue();
+        } else if (propertyValue instanceof InternalNumericMetricsAggregation.SingleValue) {
+            return ((InternalNumericMetricsAggregation.SingleValue) propertyValue).value();
+        } else {
+            throw new AggregationExecutionException(DerivativeParser.BUCKETS_PATH.getPreferredName()
+                    + "must reference either a number value or a single value numeric metric aggregation");
+        }
+    }
+
     @Override
     public void doReadFrom(StreamInput in) throws IOException {
         bucketsPath = in.readString();