[Aggregations] Meta data support

This commit adds the ability to associate a bit of state with each
individual aggregation.

The aggregation response can be hard to stitch back together without
having a reference to the aggregation request. In many cases this is not
available, many json serializer frameworks cache types globally or have a
static deserialisation override mechanism. In these cases making the
original request available, if at all possible, would be a hack.

The old facets returned `_type` which was just enough metadata to know
what the originating facet type in the request was.

This PR takes `_type` one step further by introducing ANY arbitrary meta
data. This could be further <strike>ab</strike>used for instance by
generic/automated aggregations that include UI state (color information,
thresholds, user input states, etc) per aggregation.

Author: Mpdreamz

docs/reference/search/aggregations.asciidoc

@@ -42,6 +42,7 @@ The following snippet captures the basic structure of aggregations:
         "<aggregation_type>" : {
             <aggregation_body>
         }
+        [,"meta" : {  [<meta_data_body>] } ]?
         [,"aggregations" : { [<sub_aggregation>]+ } ]?
     }
     [,"<aggregation_name_2>" : { ... } ]*
@@ -148,6 +149,49 @@ $ curl -XGET 'http://localhost:9200/twitter/tweet/_search?search_type=count' -d
 Setting `search_type` to `count` avoids executing the fetch phase of the search making the request more efficient.  See 
 <<search-request-search-type>> for more information on the `search_type` parameter.
 
+[float]
+=== Metadata
+
+You can associate a piece of metadata with individual aggregations at request time that will be returned in place
+at response time.
+
+Consider this example where we want to associate the color blue with our `terms` aggregation.
+
+[source,js]
+--------------------------------------------------
+{
+    ...
+    aggs": {
+        "titles": {
+            "terms": {
+                "field": "title"
+            },
+            "meta": {
+                "color": "blue"
+            },
+        }
+    }
+}
+--------------------------------------------------
+
+Then that piece of metadata will be returned in place for our `titles` terms aggregation
+
+[source,js]
+--------------------------------------------------
+{
+    ...
+    "aggregations": {
+        "titles": {
+            "meta": {
+                "color" : "blue"
+            },
+            "buckets": [
+            ]
+        }
+    }
+}
+--------------------------------------------------
+
 include::aggregations/metrics.asciidoc[]
 
 include::aggregations/bucket.asciidoc[]

src/main/java/org/elasticsearch/search/aggregations/Aggregation.java

@@ -18,6 +18,8 @@
  */
 package org.elasticsearch.search.aggregations;
 
+import java.util.Map;
+
 /**
  * An aggregation
  */
@@ -28,4 +30,8 @@ public interface Aggregation {
      */
     String getName();
 
+    /**
+     * Get the optional byte array metadata that was set on the aggregation
+     */
+    Map<String, Object> getMetaData();
 }

src/main/java/org/elasticsearch/search/aggregations/AggregationBuilder.java

@@ -38,6 +38,7 @@ public abstract class AggregationBuilder<B extends AggregationBuilder<B>> extend
 
     private List<AbstractAggregationBuilder> aggregations;
     private BytesReference aggregationsBinary;
+    private Map<String, Object> metaData;
 
     /**
      * Sole constructor, typically used by sub-classes.
@@ -101,10 +102,21 @@ public B subAggregation(Map<String, Object> aggs) {
         }
     }
 
+    /**
+     * Sets the meta data to be included in the aggregation response
+     */
+    public B setMetaData(Map<String, Object> metaData) {
+        this.metaData = metaData;
+        return (B)this;
+    }
+
     @Override
     public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject(getName());
 
+        if (this.metaData != null) {
+            builder.field("meta", this.metaData);
+        }
         builder.field(type);
         internalXContent(builder, params);
 

src/main/java/org/elasticsearch/search/aggregations/Aggregator.java

@@ -44,6 +44,7 @@ public boolean apply(Aggregator aggregator) {
             return aggregator.shouldCollect();
         }
     };
+    private final Map<String, Object> metaData;
 
     /**
      * Returns whether any of the parent aggregators has {@link BucketAggregationMode#PER_BUCKET} as a bucket aggregation mode.
@@ -60,6 +61,10 @@ public static boolean hasParentBucketAggregator(Aggregator parent) {
 
     public static final ParseField COLLECT_MODE = new ParseField("collect_mode");
 
+    public Map<String, Object> getMetaData() {
+        return this.metaData;
+    }
+
     /**
      * Defines the nature of the aggregator's aggregation execution when nested in other aggregators and the buckets they create.
      */
@@ -177,9 +182,11 @@ public int nextDoc() throws IOException {
      * @param estimatedBucketsCount When served as a sub-aggregator, indicate how many buckets the parent aggregator will generate.
      * @param context               The aggregation context
      * @param parent                The parent aggregator (may be {@code null} for top level aggregators)
+     * @param metaData              The metaData associated with this aggregator
      */
-    protected Aggregator(String name, BucketAggregationMode bucketAggregationMode, AggregatorFactories factories, long estimatedBucketsCount, AggregationContext context, Aggregator parent) {
+    protected Aggregator(String name, BucketAggregationMode bucketAggregationMode, AggregatorFactories factories, long estimatedBucketsCount, AggregationContext context, Aggregator parent, Map<String, Object> metaData) {
         this.name = name;
+        this.metaData = metaData;
         this.parent = parent;
         this.estimatedBucketCount = estimatedBucketsCount;
         this.context = context;
@@ -217,6 +224,7 @@ public void gatherAnalysis(BucketAnalysisCollector results, long bucketOrdinal)
             }
         };
     }
+
     protected void preCollection() {
         Iterable<Aggregator> collectables = Iterables.filter(Arrays.asList(subAggregators), COLLECTABLE_AGGREGATOR);
         List<BucketCollector> nextPassCollectors = new ArrayList<>();
@@ -362,9 +370,6 @@ public void gatherAnalysis(BucketAnalysisCollector results, long bucketOrdinal)
         results.add(buildAggregation(bucketOrdinal));
     }
 
-    
-    
-
     public abstract InternalAggregation buildEmptyAggregation();
 
     protected final InternalAggregations buildEmptySubAggregations() {

src/main/java/org/elasticsearch/search/aggregations/AggregatorFactories.java

@@ -75,7 +75,7 @@ public Aggregator[] createSubAggregators(Aggregator parent, final long estimated
                 continue;
             }
             // the aggregator doesn't support multiple ordinals, let's wrap it so that it does.
-            aggregators[i] = new Aggregator(first.name(), BucketAggregationMode.MULTI_BUCKETS, AggregatorFactories.EMPTY, 1, first.context(), first.parent()) {
+            aggregators[i] = new Aggregator(first.name(), BucketAggregationMode.MULTI_BUCKETS, AggregatorFactories.EMPTY, 1, first.context(), first.parent(), first.getMetaData()) {
 
                 ObjectArray<Aggregator> aggregators;
 

src/main/java/org/elasticsearch/search/aggregations/AggregatorFactory.java

@@ -20,6 +20,8 @@
 
 import org.elasticsearch.search.aggregations.support.AggregationContext;
 
+import java.util.Map;
+
 /**
  * A factory that knows how to create an {@link Aggregator} of a specific type.
  */
@@ -29,6 +31,7 @@ public abstract class AggregatorFactory {
     protected String type;
     protected AggregatorFactory parent;
     protected AggregatorFactories factories = AggregatorFactories.EMPTY;
+    protected Map<String, Object> metaData;
 
     /**
      * Constructs a new aggregator factory.
@@ -79,9 +82,17 @@ public AggregatorFactory parent() {
      *
      * @return                      The created aggregator
      */
-    public abstract Aggregator create(AggregationContext context, Aggregator parent, long expectedBucketsCount);
+    protected abstract Aggregator createInternal(AggregationContext context, Aggregator parent, long expectedBucketsCount, Map<String, Object> metaData);
+
+    public Aggregator create(AggregationContext context, Aggregator parent, long expectedBucketsCount) {
+        Aggregator aggregator = createInternal(context, parent, expectedBucketsCount, this.metaData);
+        return aggregator;
+    }
 
     public void doValidate() {
     }
 
+    public void setMetaData(Map<String, Object> metaData) {
+        this.metaData = metaData;
+    }
 }

src/main/java/org/elasticsearch/search/aggregations/AggregatorParsers.java

@@ -26,6 +26,7 @@
 import org.elasticsearch.search.internal.SearchContext;
 
 import java.io.IOException;
+import java.util.Map;
 import java.util.Set;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -100,6 +101,8 @@ private AggregatorFactories parseAggregators(XContentParser parser, SearchContex
             AggregatorFactory factory = null;
             AggregatorFactories subFactories = null;
 
+            Map<String, Object> metaData = null;
+
             while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
                 if (token != XContentParser.Token.FIELD_NAME) {
                     throw new SearchParseException(context, "Expected [" + XContentParser.Token.FIELD_NAME + "] under a [" + XContentParser.Token.START_OBJECT + "], but got a [" + token + "] in [" + aggregationName + "]");
@@ -112,6 +115,9 @@ private AggregatorFactories parseAggregators(XContentParser parser, SearchContex
                 }
 
                 switch (fieldName) {
+                    case "meta":
+                        metaData = parser.map();
+                        break;
                     case "aggregations":
                     case "aggs":
                         if (subFactories != null) {
@@ -135,6 +141,10 @@ private AggregatorFactories parseAggregators(XContentParser parser, SearchContex
                 throw new SearchParseException(context, "Missing definition for aggregation [" + aggregationName + "]");
             }
 
+            if (metaData != null) {
+                factory.setMetaData(metaData);
+            }
+
             if (subFactories != null) {
                 factory.subFactories(subFactories);
             }

src/main/java/org/elasticsearch/search/aggregations/InternalAggregation.java

@@ -18,6 +18,7 @@
  */
 package org.elasticsearch.search.aggregations;
 
+import org.elasticsearch.Version;
 import org.elasticsearch.common.bytes.BytesArray;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.io.stream.StreamInput;
@@ -31,12 +32,14 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Map;
 
 /**
  * An internal implementation of {@link Aggregation}. Serves as a base class for all aggregation implementations.
  */
 public abstract class InternalAggregation implements Aggregation, ToXContent, Streamable {
 
+
     /**
      * The aggregation type that holds all the string types that are associated with an aggregation:
      * <ul>
@@ -111,6 +114,8 @@ public ScriptService scriptService() {
 
     protected String name;
 
+    protected Map<String, Object> metaData;
+
     /** Constructs an un initialized addAggregation (used for serialization) **/
     protected InternalAggregation() {}
 
@@ -119,8 +124,9 @@ protected InternalAggregation() {}
      *
      * @param name The name of the get.
      */
-    protected InternalAggregation(String name) {
+    protected InternalAggregation(String name, Map<String, Object> metaData) {
         this.name = name;
+        this.metaData = metaData;
     }
 
     @Override
@@ -158,21 +164,50 @@ protected static void writeSize(int size, StreamOutput out) throws IOException {
         }
         out.writeVInt(size);
     }
-    
+
+    public Map<String, Object> getMetaData() {
+        return metaData;
+    }
+
     @Override
     public final XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject(name);
+        if (this.metaData != null) {
+            builder.field(CommonFields.META);
+            builder.map(this.metaData);
+        }
         doXContentBody(builder, params);
         builder.endObject();
         return builder;
     }
 
     public abstract XContentBuilder doXContentBody(XContentBuilder builder, Params params) throws IOException;
 
+    public final void writeTo(StreamOutput out) throws IOException {
+        out.writeString(name);
+        if (out.getVersion().onOrAfter(Version.V_1_5_0)) {
+            out.writeGenericValue(metaData);
+        }
+        doWriteTo(out);
+    }
+
+    protected abstract void doWriteTo(StreamOutput out) throws IOException;
+
+    public final void readFrom(StreamInput in) throws IOException {
+        name = in.readString();
+        if (in.getVersion().onOrAfter(Version.V_1_5_0)) {
+            metaData = in.readMap();
+        }
+        doReadFrom(in);
+    }
+
+    protected abstract void doReadFrom(StreamInput in) throws IOException;
+
     /**
      * Common xcontent fields that are shared among addAggregation
      */
     public static final class CommonFields {
+        public static final XContentBuilderString META = new XContentBuilderString("meta");
         public static final XContentBuilderString BUCKETS = new XContentBuilderString("buckets");
         public static final XContentBuilderString VALUE = new XContentBuilderString("value");
         public static final XContentBuilderString VALUES = new XContentBuilderString("values");

src/main/java/org/elasticsearch/search/aggregations/NonCollectingAggregator.java

@@ -23,15 +23,16 @@
 import org.elasticsearch.search.aggregations.support.AggregationContext;
 
 import java.io.IOException;
+import java.util.Map;
 
 /**
  * An aggregator that is not collected, this can typically be used when running an aggregation over a field that doesn't have
  * a mapping.
  */
 public abstract class NonCollectingAggregator extends Aggregator {
 
-    protected NonCollectingAggregator(String name, AggregationContext context, Aggregator parent) {
-        super(name, BucketAggregationMode.MULTI_BUCKETS, AggregatorFactories.EMPTY, 0, context, parent);
+    protected NonCollectingAggregator(String name, AggregationContext context, Aggregator parent, Map<String, Object> metaData) {
+        super(name, BucketAggregationMode.MULTI_BUCKETS, AggregatorFactories.EMPTY, 0, context, parent, metaData);
     }
 
     private void fail() {

src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java

@@ -26,6 +26,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Map;
 
 /**
  *
@@ -35,8 +36,8 @@ public abstract class BucketsAggregator extends Aggregator {
     private IntArray docCounts;
 
     public BucketsAggregator(String name, BucketAggregationMode bucketAggregationMode, AggregatorFactories factories,
-                             long estimatedBucketsCount, AggregationContext context, Aggregator parent) {
-        super(name, bucketAggregationMode, factories, estimatedBucketsCount, context, parent);
+                             long estimatedBucketsCount, AggregationContext context, Aggregator parent, Map<String, Object> metaData) {
+        super(name, bucketAggregationMode, factories, estimatedBucketsCount, context, parent, metaData);
         docCounts = bigArrays.newIntArray(estimatedBucketsCount, true);
     }