Ensure source filtering automatons are only compiled once (#20857)

This change adds a overloaded `XContentMapValues#filter` method that returns
a function enclosing the compiled automatons that can be reused across filter
calls. This for instance prevents compiling automatons over and over again when
hits are filtered or in the SourceFieldMapper for each document.

Closes #20839

19 files changed, 128 insertions, 149 deletions

diff --git a/buildSrc/src/main/resources/checkstyle_suppressions.xml b/buildSrc/src/main/resources/checkstyle_suppressions.xml
index b3d9b6a3f7..28f4360f33 100644
--- a/buildSrc/src/main/resources/checkstyle_suppressions.xml
+++ b/buildSrc/src/main/resources/checkstyle_suppressions.xml
@@ -880,7 +880,6 @@
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]indices[/\\]store[/\\]IndicesStoreIntegrationIT.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]indices[/\\]store[/\\]IndicesStoreTests.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]indices[/\\]template[/\\]SimpleIndexTemplateIT.java" checks="LineLength" />
-  <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]mget[/\\]SimpleMgetIT.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]monitor[/\\]jvm[/\\]JvmGcMonitorServiceSettingsTests.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]plugins[/\\]PluginInfoTests.java" checks="LineLength" />
   <suppress files="core[/\\]src[/\\]test[/\\]java[/\\]org[/\\]elasticsearch[/\\]plugins[/\\]PluginsServiceTests.java" checks="LineLength" />
diff --git a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
index cf7b482181..d2d9bb3b82 100644
--- a/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
+++ b/core/src/main/java/org/elasticsearch/action/explain/ExplainRequestBuilder.java
@@ -99,12 +99,9 @@ public class ExplainRequestBuilder extends SingleShardOperationRequestBuilder<Ex
      * Indicates whether the response should contain the stored _source
      */
     public ExplainRequestBuilder setFetchSource(boolean fetch) {
-        FetchSourceContext context = request.fetchSourceContext();
-        if (context == null) {
-            request.fetchSourceContext(new FetchSourceContext(fetch));
-        } else {
-            context.fetchSource(fetch);
-        }
+        FetchSourceContext fetchSourceContext = request.fetchSourceContext() != null ? request.fetchSourceContext()
+            : FetchSourceContext.FETCH_SOURCE;
+        request.fetchSourceContext(new FetchSourceContext(fetch, fetchSourceContext.includes(), fetchSourceContext.excludes()));
         return this;
     }
 
@@ -129,14 +126,9 @@ public class ExplainRequestBuilder extends SingleShardOperationRequestBuilder<Ex
      * @param excludes An optional list of exclude (optionally wildcarded) pattern to filter the returned _source
      */
     public ExplainRequestBuilder setFetchSource(@Nullable String[] includes, @Nullable String[] excludes) {
-        FetchSourceContext context = request.fetchSourceContext();
-        if (context == null) {
-            request.fetchSourceContext(new FetchSourceContext(includes, excludes));
-        } else {
-            context.fetchSource(true);
-            context.includes(includes);
-            context.excludes(excludes);
-        }
+        FetchSourceContext fetchSourceContext = request.fetchSourceContext() != null ? request.fetchSourceContext()
+            : FetchSourceContext.FETCH_SOURCE;
+        request.fetchSourceContext(new FetchSourceContext(fetchSourceContext.fetchSource(), includes, excludes));
         return this;
     }
 }
diff --git a/core/src/main/java/org/elasticsearch/action/get/GetRequestBuilder.java b/core/src/main/java/org/elasticsearch/action/get/GetRequestBuilder.java
index f56905d86e..973b130bed 100644
--- a/core/src/main/java/org/elasticsearch/action/get/GetRequestBuilder.java
+++ b/core/src/main/java/org/elasticsearch/action/get/GetRequestBuilder.java
@@ -99,12 +99,8 @@ public class GetRequestBuilder extends SingleShardOperationRequestBuilder<GetReq
      * @return this for chaining
      */
     public GetRequestBuilder setFetchSource(boolean fetch) {
-        FetchSourceContext context = request.fetchSourceContext();
-        if (context == null) {
-            request.fetchSourceContext(new FetchSourceContext(fetch));
-        } else {
-            context.fetchSource(fetch);
-        }
+        FetchSourceContext context = request.fetchSourceContext() == null ? FetchSourceContext.FETCH_SOURCE : request.fetchSourceContext();
+        request.fetchSourceContext(new FetchSourceContext(fetch, context.includes(), context.excludes()));
         return this;
     }
 
@@ -129,14 +125,8 @@ public class GetRequestBuilder extends SingleShardOperationRequestBuilder<GetReq
      * @param excludes An optional list of exclude (optionally wildcarded) pattern to filter the returned _source
      */
     public GetRequestBuilder setFetchSource(@Nullable String[] includes, @Nullable String[] excludes) {
-        FetchSourceContext context = request.fetchSourceContext();
-        if (context == null) {
-            request.fetchSourceContext(new FetchSourceContext(includes, excludes));
-        } else {
-            context.fetchSource(true);
-            context.includes(includes);
-            context.excludes(excludes);
-        }
+        FetchSourceContext context = request.fetchSourceContext() == null ? FetchSourceContext.FETCH_SOURCE : request.fetchSourceContext();
+        request.fetchSourceContext(new FetchSourceContext(context.fetchSource(), includes, excludes));
         return this;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java b/core/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
index a0fa4025ec..1308d56aca 100644
--- a/core/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
+++ b/core/src/main/java/org/elasticsearch/action/get/MultiGetRequest.java
@@ -370,7 +370,7 @@ public class MultiGetRequest extends ActionRequest<MultiGetRequest> implements I
             long version = Versions.MATCH_ANY;
             VersionType versionType = VersionType.INTERNAL;
 
-            FetchSourceContext fetchSourceContext = null;
+            FetchSourceContext fetchSourceContext = FetchSourceContext.FETCH_SOURCE;
 
             while ((token = parser.nextToken()) != XContentParser.Token.END_OBJECT) {
                 if (token == XContentParser.Token.FIELD_NAME) {
@@ -401,9 +401,11 @@ public class MultiGetRequest extends ActionRequest<MultiGetRequest> implements I
                         versionType = VersionType.fromString(parser.text());
                     } else if ("_source".equals(currentFieldName)) {
                         if (parser.isBooleanValue()) {
-                            fetchSourceContext = new FetchSourceContext(parser.booleanValue());
+                            fetchSourceContext = new FetchSourceContext(parser.booleanValue(), fetchSourceContext.includes(),
+                                fetchSourceContext.excludes());
                         } else if (token == XContentParser.Token.VALUE_STRING) {
-                            fetchSourceContext = new FetchSourceContext(new String[]{parser.text()});
+                            fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource(),
+                                new String[]{parser.text()}, fetchSourceContext.excludes());
                         } else {
                             throw new ElasticsearchParseException("illegal type for _source: [{}]", token);
                         }
@@ -422,7 +424,8 @@ public class MultiGetRequest extends ActionRequest<MultiGetRequest> implements I
                         while ((token = parser.nextToken()) != XContentParser.Token.END_ARRAY) {
                             includes.add(parser.text());
                         }
-                        fetchSourceContext = new FetchSourceContext(includes.toArray(Strings.EMPTY_ARRAY));
+                        fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource(), includes.toArray(Strings.EMPTY_ARRAY)
+                            , fetchSourceContext.excludes());
                     }
 
                 } else if (token == XContentParser.Token.START_OBJECT) {
@@ -450,7 +453,7 @@ public class MultiGetRequest extends ActionRequest<MultiGetRequest> implements I
                             }
                         }
 
-                        fetchSourceContext = new FetchSourceContext(
+                        fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource(),
                                 includes == null ? Strings.EMPTY_ARRAY : includes.toArray(new String[includes.size()]),
                                 excludes == null ? Strings.EMPTY_ARRAY : excludes.toArray(new String[excludes.size()]));
                     }
@@ -463,7 +466,7 @@ public class MultiGetRequest extends ActionRequest<MultiGetRequest> implements I
                 aFields = defaultFields;
             }
             items.add(new Item(index, type, id).routing(routing).storedFields(aFields).parent(parent).version(version).versionType(versionType)
-                    .fetchSourceContext(fetchSourceContext == null ? defaultFetchSource : fetchSourceContext));
+                    .fetchSourceContext(fetchSourceContext == FetchSourceContext.FETCH_SOURCE ? defaultFetchSource : fetchSourceContext));
         }
     }
 
diff --git a/core/src/main/java/org/elasticsearch/action/update/UpdateHelper.java b/core/src/main/java/org/elasticsearch/action/update/UpdateHelper.java
index 3649f17c48..15c2d3a86b 100644
--- a/core/src/main/java/org/elasticsearch/action/update/UpdateHelper.java
+++ b/core/src/main/java/org/elasticsearch/action/update/UpdateHelper.java
@@ -307,7 +307,7 @@ public class UpdateHelper extends AbstractComponent {
         if (request.fetchSource() != null && request.fetchSource().fetchSource()) {
             sourceRequested = true;
             if (request.fetchSource().includes().length > 0 || request.fetchSource().excludes().length > 0) {
-                Object value = sourceLookup.filter(request.fetchSource().includes(), request.fetchSource().excludes());
+                Object value = sourceLookup.filter(request.fetchSource());
                 try {
                     final int initialCapacity = Math.min(1024, sourceAsBytes.length());
                     BytesStreamOutput streamOutput = new BytesStreamOutput(initialCapacity);
diff --git a/core/src/main/java/org/elasticsearch/action/update/UpdateRequest.java b/core/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
index 3ec2398d2f..f3db4e4ea1 100644
--- a/core/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
+++ b/core/src/main/java/org/elasticsearch/action/update/UpdateRequest.java
@@ -400,7 +400,8 @@ public class UpdateRequest extends InstanceShardOperationRequest<UpdateRequest>
      *            the returned _source
      */
     public UpdateRequest fetchSource(@Nullable String include, @Nullable String exclude) {
-        this.fetchSourceContext = new FetchSourceContext(include, exclude);
+        FetchSourceContext context = this.fetchSourceContext == null ? FetchSourceContext.FETCH_SOURCE : this.fetchSourceContext;
+        this.fetchSourceContext = new FetchSourceContext(context.fetchSource(), new String[] {include}, new String[]{exclude});
         return this;
     }
 
@@ -417,7 +418,8 @@ public class UpdateRequest extends InstanceShardOperationRequest<UpdateRequest>
      *            filter the returned _source
      */
     public UpdateRequest fetchSource(@Nullable String[] includes, @Nullable String[] excludes) {
-        this.fetchSourceContext = new FetchSourceContext(includes, excludes);
+        FetchSourceContext context = this.fetchSourceContext == null ? FetchSourceContext.FETCH_SOURCE : this.fetchSourceContext;
+        this.fetchSourceContext = new FetchSourceContext(context.fetchSource(), includes, excludes);
         return this;
     }
 
@@ -425,7 +427,8 @@ public class UpdateRequest extends InstanceShardOperationRequest<UpdateRequest>
      * Indicates whether the response should contain the updated _source.
      */
     public UpdateRequest fetchSource(boolean fetchSource) {
-        this.fetchSourceContext = new FetchSourceContext(fetchSource);
+        FetchSourceContext context = this.fetchSourceContext == null ? FetchSourceContext.FETCH_SOURCE : this.fetchSourceContext;
+        this.fetchSourceContext = new FetchSourceContext(fetchSource, context.includes(), context.excludes());
         return this;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/common/xcontent/support/XContentMapValues.java b/core/src/main/java/org/elasticsearch/common/xcontent/support/XContentMapValues.java
index fa211bb08e..f1eb9228d0 100644
--- a/core/src/main/java/org/elasticsearch/common/xcontent/support/XContentMapValues.java
+++ b/core/src/main/java/org/elasticsearch/common/xcontent/support/XContentMapValues.java
@@ -33,6 +33,7 @@ import java.util.Arrays;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 /**
  *
@@ -155,6 +156,14 @@ public class XContentMapValues {
      * then {@code a.b} will be kept in the filtered map.
      */
     public static Map<String, Object> filter(Map<String, ?> map, String[] includes, String[] excludes) {
+        return filter(includes, excludes).apply(map);
+    }
+
+    /**
+     * Returns a function that filters a document map based on the given include and exclude rules.
+     * @see #filter(Map, String[], String[]) for details
+     */
+    public static Function<Map<String, ?>, Map<String, Object>> filter(String[] includes, String[] excludes) {
         CharacterRunAutomaton matchAllAutomaton = new CharacterRunAutomaton(Automata.makeAnyString());
 
         CharacterRunAutomaton include;
@@ -178,10 +187,10 @@ public class XContentMapValues {
         // NOTE: We cannot use Operations.minus because of the special case that
         // we want all sub properties to match as soon as an object matches
 
-        return filter(map,
-                include, include.getInitialState(),
-                exclude, exclude.getInitialState(),
-                matchAllAutomaton);
+        return (map) -> filter(map,
+            include, include.getInitialState(),
+            exclude, exclude.getInitialState(),
+            matchAllAutomaton);
     }
 
     /** Make matches on objects also match dots in field names.
diff --git a/core/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java b/core/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
index 63d4d958b3..9242f5e94c 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/SourceFieldMapper.java
@@ -45,6 +45,7 @@ import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 import static org.elasticsearch.common.xcontent.support.XContentMapValues.lenientNodeBooleanValue;
 
@@ -56,6 +57,7 @@ public class SourceFieldMapper extends MetadataFieldMapper {
     public static final String NAME = "_source";
 
     public static final String CONTENT_TYPE = "_source";
+    private final Function<Map<String, ?>, Map<String, Object>> filter;
 
     public static class Defaults {
         public static final String NAME = SourceFieldMapper.NAME;
@@ -190,6 +192,8 @@ public class SourceFieldMapper extends MetadataFieldMapper {
         this.enabled = enabled;
         this.includes = includes;
         this.excludes = excludes;
+        final boolean filtered = (includes != null && includes.length > 0) || (excludes != null && excludes.length > 0);
+        this.filter = enabled && filtered && fieldType().stored() ? XContentMapValues.filter(includes, excludes) : null;
         this.complete = enabled && includes == null && excludes == null;
     }
 
@@ -239,12 +243,10 @@ public class SourceFieldMapper extends MetadataFieldMapper {
             return;
         }
 
-        boolean filtered = (includes != null && includes.length > 0) || (excludes != null && excludes.length > 0);
-        if (filtered) {
+        if (filter != null) {
             // we don't update the context source if we filter, we want to keep it as is...
-
             Tuple<XContentType, Map<String, Object>> mapTuple = XContentHelper.convertToMap(source, true);
-            Map<String, Object> filteredSource = XContentMapValues.filter(mapTuple.v2(), includes, excludes);
+            Map<String, Object> filteredSource = filter.apply(mapTuple.v2());
             BytesStreamOutput bStream = new BytesStreamOutput();
             XContentType contentType = mapTuple.v1();
             XContentBuilder builder = XContentFactory.contentBuilder(contentType, bStream).map(filteredSource);
diff --git a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/tophits/TopHitsAggregationBuilder.java b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/tophits/TopHitsAggregationBuilder.java
index 9f740b695b..70f1adc771 100644
--- a/core/src/main/java/org/elasticsearch/search/aggregations/metrics/tophits/TopHitsAggregationBuilder.java
+++ b/core/src/main/java/org/elasticsearch/search/aggregations/metrics/tophits/TopHitsAggregationBuilder.java
@@ -283,11 +283,9 @@ public class TopHitsAggregationBuilder extends AbstractAggregationBuilder<TopHit
      * every hit
      */
     public TopHitsAggregationBuilder fetchSource(boolean fetch) {
-        if (this.fetchSourceContext == null) {
-            this.fetchSourceContext = new FetchSourceContext(fetch);
-        } else {
-            this.fetchSourceContext.fetchSource(fetch);
-        }
+        FetchSourceContext fetchSourceContext = this.fetchSourceContext != null ? this.fetchSourceContext
+            : FetchSourceContext.FETCH_SOURCE;
+        this.fetchSourceContext = new FetchSourceContext(fetch, fetchSourceContext.includes(), fetchSourceContext.excludes());
         return this;
     }
 
@@ -322,7 +320,9 @@ public class TopHitsAggregationBuilder extends AbstractAggregationBuilder<TopHit
      *            pattern to filter the returned _source
      */
     public TopHitsAggregationBuilder fetchSource(@Nullable String[] includes, @Nullable String[] excludes) {
-        fetchSourceContext = new FetchSourceContext(includes, excludes);
+        FetchSourceContext fetchSourceContext = this.fetchSourceContext != null ? this.fetchSourceContext
+            : FetchSourceContext.FETCH_SOURCE;
+        this.fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource(), includes, excludes);
         return this;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java b/core/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java
index c64a5fd552..1f88da63cc 100644
--- a/core/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java
+++ b/core/src/main/java/org/elasticsearch/search/builder/SearchSourceBuilder.java
@@ -637,11 +637,9 @@ public final class SearchSourceBuilder extends ToXContentToBytes implements Writ
      * every hit
      */
     public SearchSourceBuilder fetchSource(boolean fetch) {
-        if (this.fetchSourceContext == null) {
-            this.fetchSourceContext = new FetchSourceContext(fetch);
-        } else {
-            this.fetchSourceContext.fetchSource(fetch);
-        }
+        FetchSourceContext fetchSourceContext = this.fetchSourceContext != null ? this.fetchSourceContext
+            : FetchSourceContext.FETCH_SOURCE;
+        this.fetchSourceContext = new FetchSourceContext(fetch, fetchSourceContext.includes(), fetchSourceContext.excludes());
         return this;
     }
 
@@ -675,7 +673,9 @@ public final class SearchSourceBuilder extends ToXContentToBytes implements Writ
      *            filter the returned _source
      */
     public SearchSourceBuilder fetchSource(@Nullable String[] includes, @Nullable String[] excludes) {
-        fetchSourceContext = new FetchSourceContext(includes, excludes);
+        FetchSourceContext fetchSourceContext = this.fetchSourceContext != null ? this.fetchSourceContext
+            : FetchSourceContext.FETCH_SOURCE;
+        this.fetchSourceContext = new FetchSourceContext(fetchSourceContext.fetchSource(), includes, excludes);
         return this;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java b/core/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
index 41ea0e294d..ef6fd979a6 100644
--- a/core/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
+++ b/core/src/main/java/org/elasticsearch/search/fetch/FetchPhase.java
@@ -99,11 +99,9 @@ public class FetchPhase implements SearchPhase {
         } else {
             for (String fieldName : context.storedFieldsContext().fieldNames()) {
                 if (fieldName.equals(SourceFieldMapper.NAME)) {
-                    if (context.hasFetchSourceContext()) {
-                        context.fetchSourceContext().fetchSource(true);
-                    } else {
-                        context.fetchSourceContext(new FetchSourceContext(true));
-                    }
+                    FetchSourceContext fetchSourceContext = context.hasFetchSourceContext() ? context.fetchSourceContext()
+                        : FetchSourceContext.FETCH_SOURCE;
+                    context.fetchSourceContext(new FetchSourceContext(true, fetchSourceContext.includes(), fetchSourceContext.excludes()));
                     continue;
                 }
                 if (Regex.isSimpleMatchPattern(fieldName)) {
diff --git a/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceContext.java b/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceContext.java
index 212f8d724d..1eec405502 100644
--- a/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceContext.java
+++ b/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceContext.java
@@ -30,12 +30,15 @@ import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
+import org.elasticsearch.common.xcontent.support.XContentMapValues;
 import org.elasticsearch.rest.RestRequest;
 
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Map;
+import java.util.function.Function;
 
 /**
  * Context used to fetch the {@code _source}.
@@ -47,39 +50,13 @@ public class FetchSourceContext implements Writeable, ToXContent {
 
     public static final FetchSourceContext FETCH_SOURCE = new FetchSourceContext(true);
     public static final FetchSourceContext DO_NOT_FETCH_SOURCE = new FetchSourceContext(false);
-    private boolean fetchSource;
-    private String[] includes;
-    private String[] excludes;
+    private final boolean fetchSource;
+    private final String[] includes;
+    private final String[] excludes;
+    private Function<Map<String, ?>, Map<String, Object>> filter;
 
     public static FetchSourceContext parse(XContentParser parser) throws IOException {
-        FetchSourceContext fetchSourceContext = new FetchSourceContext();
-        fetchSourceContext.fromXContent(parser, ParseFieldMatcher.STRICT);
-        return fetchSourceContext;
-    }
-
-    public FetchSourceContext() {
-    }
-
-    public FetchSourceContext(boolean fetchSource) {
-        this(fetchSource, Strings.EMPTY_ARRAY, Strings.EMPTY_ARRAY);
-    }
-
-    public FetchSourceContext(String include) {
-        this(include, null);
-    }
-
-    public FetchSourceContext(String include, String exclude) {
-        this(true,
-                include == null ? Strings.EMPTY_ARRAY : new String[]{include},
-                exclude == null ? Strings.EMPTY_ARRAY : new String[]{exclude});
-    }
-
-    public FetchSourceContext(String[] includes) {
-        this(true, includes, Strings.EMPTY_ARRAY);
-    }
-
-    public FetchSourceContext(String[] includes, String[] excludes) {
-        this(true, includes, excludes);
+        return fromXContent(parser, ParseFieldMatcher.STRICT);
     }
 
     public FetchSourceContext(boolean fetchSource, String[] includes, String[] excludes) {
@@ -88,6 +65,10 @@ public class FetchSourceContext implements Writeable, ToXContent {
         this.excludes = excludes == null ? Strings.EMPTY_ARRAY : excludes;
     }
 
+    public FetchSourceContext(boolean fetchSource) {
+        this(fetchSource, Strings.EMPTY_ARRAY, Strings.EMPTY_ARRAY);
+    }
+
     public FetchSourceContext(StreamInput in) throws IOException {
         fetchSource = in.readBoolean();
         includes = in.readStringArray();
@@ -105,29 +86,14 @@ public class FetchSourceContext implements Writeable, ToXContent {
         return this.fetchSource;
     }
 
-    public FetchSourceContext fetchSource(boolean fetchSource) {
-        this.fetchSource = fetchSource;
-        return this;
-    }
-
     public String[] includes() {
         return this.includes;
     }
 
-    public FetchSourceContext includes(String[] includes) {
-        this.includes = includes;
-        return this;
-    }
-
     public String[] excludes() {
         return this.excludes;
     }
 
-    public FetchSourceContext excludes(String[] excludes) {
-        this.excludes = excludes;
-        return this;
-    }
-
     public static FetchSourceContext parseFromRestRequest(RestRequest request) {
         Boolean fetchSource = null;
         String[] source_excludes = null;
@@ -161,7 +127,7 @@ public class FetchSourceContext implements Writeable, ToXContent {
         return null;
     }
 
-    public void fromXContent(XContentParser parser, ParseFieldMatcher parseFieldMatcher) throws IOException {
+    public static FetchSourceContext fromXContent(XContentParser parser, ParseFieldMatcher parseFieldMatcher) throws IOException {
         XContentParser.Token token = parser.currentToken();
         boolean fetchSource = true;
         String[] includes = Strings.EMPTY_ARRAY;
@@ -226,9 +192,7 @@ public class FetchSourceContext implements Writeable, ToXContent {
             throw new ParsingException(parser.getTokenLocation(), "Expected one of [" + XContentParser.Token.VALUE_BOOLEAN + ", "
                     + XContentParser.Token.START_OBJECT + "] but found [" + token + "]", parser.getTokenLocation());
         }
-        this.fetchSource = fetchSource;
-        this.includes = includes;
-        this.excludes = excludes;
+        return new FetchSourceContext(fetchSource, includes, excludes);
     }
 
     @Override
@@ -265,4 +229,15 @@ public class FetchSourceContext implements Writeable, ToXContent {
         result = 31 * result + (excludes != null ? Arrays.hashCode(excludes) : 0);
         return result;
     }
+
+    /**
+     * Returns a filter function that expects the source map as an input and returns
+     * the filtered map.
+     */
+    public Function<Map<String, ?>, Map<String, Object>> getFilter() {
+        if (filter == null) {
+            filter = XContentMapValues.filter(includes, excludes);
+        }
+        return filter;
+    }
 }
diff --git a/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhase.java b/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhase.java
index fe5a9f286c..3171ca4b00 100644
--- a/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhase.java
+++ b/core/src/main/java/org/elasticsearch/search/fetch/subphase/FetchSourceSubPhase.java
@@ -48,7 +48,7 @@ public final class FetchSourceSubPhase implements FetchSubPhase {
                     "for index [" + context.indexShard().shardId().getIndexName() + "]");
         }
 
-        Object value = source.filter(fetchSourceContext.includes(), fetchSourceContext.excludes());
+        final Object value = source.filter(fetchSourceContext);
         try {
             final int initialCapacity = Math.min(1024, source.internalSourceRef().length());
             BytesStreamOutput streamOutput = new BytesStreamOutput(initialCapacity);
diff --git a/core/src/main/java/org/elasticsearch/search/lookup/SourceLookup.java b/core/src/main/java/org/elasticsearch/search/lookup/SourceLookup.java
index 910f5daf7a..01610c6405 100644
--- a/core/src/main/java/org/elasticsearch/search/lookup/SourceLookup.java
+++ b/core/src/main/java/org/elasticsearch/search/lookup/SourceLookup.java
@@ -27,6 +27,7 @@ import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.common.xcontent.support.XContentMapValues;
 import org.elasticsearch.index.fieldvisitor.FieldsVisitor;
+import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 
 import java.util.Collection;
 import java.util.List;
@@ -130,8 +131,8 @@ public class SourceLookup implements Map {
         return XContentMapValues.extractRawValues(path, loadSourceIfNeeded());
     }
 
-    public Object filter(String[] includes, String[] excludes) {
-        return XContentMapValues.filter(loadSourceIfNeeded(), includes, excludes);
+    public Object filter(FetchSourceContext context) {
+        return context.getFilter().apply(loadSourceIfNeeded());
     }
 
     public Object extractValue(String path) {
diff --git a/core/src/test/java/org/elasticsearch/index/query/InnerHitBuilderTests.java b/core/src/test/java/org/elasticsearch/index/query/InnerHitBuilderTests.java
index 5f8c847e41..19252a6b80 100644
--- a/core/src/test/java/org/elasticsearch/index/query/InnerHitBuilderTests.java
+++ b/core/src/test/java/org/elasticsearch/index/query/InnerHitBuilderTests.java
@@ -236,7 +236,7 @@ public class InnerHitBuilderTests extends ESTestCase {
         if (randomBoolean()) {
             randomFetchSourceContext = new FetchSourceContext(randomBoolean());
         } else {
-            randomFetchSourceContext = new FetchSourceContext(
+            randomFetchSourceContext = new FetchSourceContext(true,
                     generateRandomStringArray(12, 16, false),
                     generateRandomStringArray(12, 16, false)
             );
@@ -322,7 +322,7 @@ public class InnerHitBuilderTests extends ESTestCase {
                     if (randomBoolean()) {
                         randomFetchSourceContext = new FetchSourceContext(randomBoolean());
                     } else {
-                        randomFetchSourceContext = new FetchSourceContext(
+                        randomFetchSourceContext = new FetchSourceContext(true,
                                 generateRandomStringArray(12, 16, false),
                                 generateRandomStringArray(12, 16, false)
                         );
diff --git a/core/src/test/java/org/elasticsearch/mget/SimpleMgetIT.java b/core/src/test/java/org/elasticsearch/mget/SimpleMgetIT.java
index e022bd7521..c8e14867d3 100644
--- a/core/src/test/java/org/elasticsearch/mget/SimpleMgetIT.java
+++ b/core/src/test/java/org/elasticsearch/mget/SimpleMgetIT.java
@@ -60,7 +60,8 @@ public class SimpleMgetIT extends ESIntegTestCase {
         assertThat(mgetResponse.getResponses()[1].getIndex(), is("nonExistingIndex"));
         assertThat(mgetResponse.getResponses()[1].isFailed(), is(true));
         assertThat(mgetResponse.getResponses()[1].getFailure().getMessage(), is("no such index"));
-        assertThat(((ElasticsearchException) mgetResponse.getResponses()[1].getFailure().getFailure()).getIndex().getName(), is("nonExistingIndex"));
+        assertThat(((ElasticsearchException) mgetResponse.getResponses()[1].getFailure().getFailure()).getIndex().getName(),
+            is("nonExistingIndex"));
 
 
         mgetResponse = client().prepareMultiGet()
@@ -70,7 +71,8 @@ public class SimpleMgetIT extends ESIntegTestCase {
         assertThat(mgetResponse.getResponses()[0].getIndex(), is("nonExistingIndex"));
         assertThat(mgetResponse.getResponses()[0].isFailed(), is(true));
         assertThat(mgetResponse.getResponses()[0].getFailure().getMessage(), is("no such index"));
-        assertThat(((ElasticsearchException) mgetResponse.getResponses()[0].getFailure().getFailure()).getIndex().getName(), is("nonExistingIndex"));
+        assertThat(((ElasticsearchException) mgetResponse.getResponses()[0].getFailure().getFailure()).getIndex().getName(),
+            is("nonExistingIndex"));
 
 
     }
@@ -119,9 +121,11 @@ public class SimpleMgetIT extends ESIntegTestCase {
         MultiGetRequestBuilder request = client().prepareMultiGet();
         for (int i = 0; i < 100; i++) {
             if (i % 2 == 0) {
-                request.add(new MultiGetRequest.Item(indexOrAlias(), "type", Integer.toString(i)).fetchSourceContext(new FetchSourceContext("included", "*.hidden_field")));
+                request.add(new MultiGetRequest.Item(indexOrAlias(), "type", Integer.toString(i))
+                    .fetchSourceContext(new FetchSourceContext(true, new String[] {"included"}, new String[] {"*.hidden_field"})));
             } else {
-                request.add(new MultiGetRequest.Item(indexOrAlias(), "type", Integer.toString(i)).fetchSourceContext(new FetchSourceContext(false)));
+                request.add(new MultiGetRequest.Item(indexOrAlias(), "type", Integer.toString(i))
+                    .fetchSourceContext(new FetchSourceContext(false)));
             }
         }
 
diff --git a/core/src/test/java/org/elasticsearch/search/AbstractSearchTestCase.java b/core/src/test/java/org/elasticsearch/search/AbstractSearchTestCase.java
index 048416c25e..e98b469f95 100644
--- a/core/src/test/java/org/elasticsearch/search/AbstractSearchTestCase.java
+++ b/core/src/test/java/org/elasticsearch/search/AbstractSearchTestCase.java
@@ -153,19 +153,20 @@ public abstract class AbstractSearchTestCase extends ESTestCase {
                     fetchSourceContext = new FetchSourceContext(randomBoolean());
                     break;
                 case 1:
-                    fetchSourceContext = new FetchSourceContext(includes, excludes);
+                    fetchSourceContext = new FetchSourceContext(true, includes, excludes);
                     break;
                 case 2:
-                    fetchSourceContext = new FetchSourceContext(randomAsciiOfLengthBetween(5, 20), randomAsciiOfLengthBetween(5, 20));
+                    fetchSourceContext = new FetchSourceContext(true, new String[]{randomAsciiOfLengthBetween(5, 20)},
+                        new String[]{randomAsciiOfLengthBetween(5, 20)});
                     break;
                 case 3:
                     fetchSourceContext = new FetchSourceContext(true, includes, excludes);
                     break;
                 case 4:
-                    fetchSourceContext = new FetchSourceContext(includes);
+                    fetchSourceContext = new FetchSourceContext(true, includes, null);
                     break;
                 case 5:
-                    fetchSourceContext = new FetchSourceContext(randomAsciiOfLengthBetween(5, 20));
+                    fetchSourceContext = new FetchSourceContext(true, new String[] {randomAsciiOfLengthBetween(5, 20)}, null);
                     break;
                 default:
                     throw new IllegalStateException();
diff --git a/core/src/test/java/org/elasticsearch/search/aggregations/metrics/TopHitsTests.java b/core/src/test/java/org/elasticsearch/search/aggregations/metrics/TopHitsTests.java
index 3f2b4c4462..98e2833903 100644
--- a/core/src/test/java/org/elasticsearch/search/aggregations/metrics/TopHitsTests.java
+++ b/core/src/test/java/org/elasticsearch/search/aggregations/metrics/TopHitsTests.java
@@ -107,26 +107,27 @@ public class TopHitsTests extends BaseAggregationTestCase<TopHitsAggregationBuil
                 excludes[i] = randomAsciiOfLengthBetween(5, 20);
             }
             switch (branch) {
-            case 0:
-                fetchSourceContext = new FetchSourceContext(randomBoolean());
-                break;
-            case 1:
-                fetchSourceContext = new FetchSourceContext(includes, excludes);
-                break;
-            case 2:
-                fetchSourceContext = new FetchSourceContext(randomAsciiOfLengthBetween(5, 20), randomAsciiOfLengthBetween(5, 20));
-                break;
-            case 3:
-                fetchSourceContext = new FetchSourceContext(true, includes, excludes);
-                break;
-            case 4:
-                fetchSourceContext = new FetchSourceContext(includes);
-                break;
-            case 5:
-                fetchSourceContext = new FetchSourceContext(randomAsciiOfLengthBetween(5, 20));
-                break;
-            default:
-                throw new IllegalStateException();
+                case 0:
+                    fetchSourceContext = new FetchSourceContext(randomBoolean());
+                    break;
+                case 1:
+                    fetchSourceContext = new FetchSourceContext(true, includes, excludes);
+                    break;
+                case 2:
+                    fetchSourceContext = new FetchSourceContext(true, new String[]{randomAsciiOfLengthBetween(5, 20)},
+                        new String[]{randomAsciiOfLengthBetween(5, 20)});
+                    break;
+                case 3:
+                    fetchSourceContext = new FetchSourceContext(true, includes, excludes);
+                    break;
+                case 4:
+                    fetchSourceContext = new FetchSourceContext(true, includes, null);
+                    break;
+                case 5:
+                    fetchSourceContext = new FetchSourceContext(true, new String[] {randomAsciiOfLengthBetween(5, 20)}, null);
+                    break;
+                default:
+                    throw new IllegalStateException();
             }
             factory.fetchSource(fetchSourceContext);
         }
diff --git a/core/src/test/java/org/elasticsearch/search/fetch/subphase/InnerHitsIT.java b/core/src/test/java/org/elasticsearch/search/fetch/subphase/InnerHitsIT.java
index 1e43ffe532..1c9a915b2a 100644
--- a/core/src/test/java/org/elasticsearch/search/fetch/subphase/InnerHitsIT.java
+++ b/core/src/test/java/org/elasticsearch/search/fetch/subphase/InnerHitsIT.java
@@ -666,7 +666,7 @@ public class InnerHitsIT extends ESIntegTestCase {
                         .innerHit(new InnerHitBuilder())).get();
         assertNoFailures(response);
         assertHitCount(response, 1);
-        SearchHit hit = response.getHits().getAt(0); 
+        SearchHit hit = response.getHits().getAt(0);
         assertThat(hit.id(), equalTo("1"));
         SearchHits messages = hit.getInnerHits().get("comments.messages");
         assertThat(messages.getTotalHits(), equalTo(1L));
@@ -982,7 +982,8 @@ public class InnerHitsIT extends ESIntegTestCase {
         // other features (like in the query dsl or aggs) in order for consistency:
         SearchResponse response = client().prepareSearch()
                 .setQuery(nestedQuery("comments", matchQuery("comments.message", "fox"), ScoreMode.None)
-                .innerHit(new InnerHitBuilder().setFetchSourceContext(new FetchSourceContext("comments.message"))))
+                .innerHit(new InnerHitBuilder().setFetchSourceContext(new FetchSourceContext(true,
+                    new String[]{"comments.message"}, null))))
                 .get();
         assertNoFailures(response);
         assertHitCount(response, 1);