Add rest_total_hits_as_int in the search APIs

This change adds the support for a search query parameter named `rest_total_hits_as_int`.
This parameter will be used in the next major version (7.0) to restore the total hits as a number
in the response. This param is added in this version (6.x) to handle mixed cluster queries where nodes
are in multiple versions (7.0 and 6.latest). The param does not change anything in 6x since total hits
is always a number in 6x so it is just ignored.

Author: jimczi

modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/RestMultiSearchTemplateAction.java

@@ -29,15 +29,24 @@
 import org.elasticsearch.rest.action.search.RestSearchAction;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Set;
 
 import static org.elasticsearch.rest.RestRequest.Method.GET;
 import static org.elasticsearch.rest.RestRequest.Method.POST;
 
 public class RestMultiSearchTemplateAction extends BaseRestHandler {
 
-    private static final Set<String> RESPONSE_PARAMS = Collections.singleton(RestSearchAction.TYPED_KEYS_PARAM);
+    private static final Set<String> RESPONSE_PARAMS;
+
+    static {
+        final Set<String> responseParams = new HashSet<>(
+            Arrays.asList(RestSearchAction.TYPED_KEYS_PARAM, RestSearchAction.TOTAL_HIT_AS_INT_PARAM)
+        );
+        RESPONSE_PARAMS = Collections.unmodifiableSet(responseParams);
+    }
 
     private final boolean allowExplicitIndex;
 

modules/lang-mustache/src/main/java/org/elasticsearch/script/mustache/RestSearchTemplateAction.java

@@ -30,15 +30,24 @@
 import org.elasticsearch.rest.action.search.RestSearchAction;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Set;
 
 import static org.elasticsearch.rest.RestRequest.Method.GET;
 import static org.elasticsearch.rest.RestRequest.Method.POST;
 
 public class RestSearchTemplateAction extends BaseRestHandler {
 
-    private static final Set<String> RESPONSE_PARAMS = Collections.singleton(RestSearchAction.TYPED_KEYS_PARAM);
+    private static final Set<String> RESPONSE_PARAMS;
+
+    static {
+        final Set<String> responseParams = new HashSet<>(
+            Arrays.asList(RestSearchAction.TYPED_KEYS_PARAM, RestSearchAction.TOTAL_HIT_AS_INT_PARAM)
+        );
+        RESPONSE_PARAMS = Collections.unmodifiableSet(responseParams);
+    }
 
     public RestSearchTemplateAction(Settings settings, RestController controller) {
         super(settings);

modules/lang-mustache/src/test/resources/rest-api-spec/test/lang_mustache/30_search_template.yml

@@ -124,3 +124,30 @@
   - match: { hits.total: 1 }
   - length: { hits.hits: 1 }
   - length: { profile: 1 }
+
+---
+"Test with rest_total_hits_as_int":
+  - skip:
+      version: " - 6.5.99"
+      reason: rest_total_hits_as_int was introduced in 6.6.0
+
+  - do:
+      index:
+        index:  test
+        type:   type
+        id:     1
+        body:   {}
+
+  - do:
+      put_script:
+        id: "template_1"
+        body: { "script": { "lang": "mustache", "source": { "query": { "match_all": {} } } } }
+
+  - match: { acknowledged: true }
+
+  - do:
+      search_template:
+        rest_total_hits_as_int: true
+        body: { "id": "template_1", "params": {} }
+
+  - match: { hits.total: 0 }

modules/lang-mustache/src/test/resources/rest-api-spec/test/lang_mustache/50_multi_search_template.yml

@@ -156,3 +156,47 @@ setup:
   - match:  { responses.0.hits.total:     2  }
   - match:  { responses.1.hits.total:     1  }
   - match:  { responses.2.hits.total:     1  }
+
+
+  - do:
+      put_script:
+        id: stored_template_1
+        body: { "script": { "lang" : "mustache", "source": { "query": {"match": {"{{field}}": "{{value}}" }}}}}
+  - match: { acknowledged: true }
+
+---
+"Test with rest_total_hits_as_int":
+  - skip:
+      version: " - 6.5.99"
+      reason: rest_total_hits_as_int was introduced in 6.6.0
+
+  - do:
+      put_script:
+        id: stored_template_1
+        body: { "script": { "lang": "mustache", "source": { "query": {"match": {"{{field}}": "{{value}}" }}}}}
+  - match: { acknowledged: true }
+
+  - do:
+      msearch_template:
+        rest_total_hits_as_int: true
+        body:
+        - index: index_*
+        - id: stored_template_1
+          params:
+            field: "foo"
+            value: "foo"
+        - index: _all
+        - id: stored_template_1
+          params:
+            field: "foo"
+            value: "bar"
+        - index: index_2
+        - id: stored_template_1
+          params:
+            field: "foo"
+            value: "foo"
+
+  - match:  { responses.0.hits.total:     2  }
+  - match:  { responses.1.hits.total:     1  }
+  - match:  { responses.2.hits.total:     1  }
+

rest-api-spec/src/main/resources/rest-api-spec/api/msearch.json

@@ -38,6 +38,11 @@
           "type" : "number",
           "description" : "The number of concurrent shard requests each sub search executes concurrently. This value should be used to limit the impact of the search on the cluster in order to limit the number of concurrent shard requests",
           "default" : "The default grows with the number of nodes in the cluster but is at most 256."
+        },
+        "rest_total_hits_as_int" : {
+          "type" : "boolean",
+          "description" : "This parameter is ignored in this version. It is used in the next major version to control whether the rest response should render the total.hits as an object or a number",
+          "default" : false
         }
       }
     },

rest-api-spec/src/main/resources/rest-api-spec/api/msearch_template.json

@@ -28,6 +28,11 @@
         "max_concurrent_searches" : {
           "type" : "number",
           "description" : "Controls the maximum number of concurrent searches the multi search api will execute"
+        },
+        "rest_total_hits_as_int" : {
+          "type" : "boolean",
+          "description" : "This parameter is ignored in this version. It is used in the next major version to control whether the rest response should render the total.hits as an object or a number",
+          "default" : false
         }
       }
     },

rest-api-spec/src/main/resources/rest-api-spec/api/scroll.json

@@ -19,6 +19,11 @@
         "scroll_id": {
           "type" : "string",
           "description" : "The scroll ID for scrolled search"
+        },
+        "rest_total_hits_as_int" : {
+          "type" : "boolean",
+          "description" : "This parameter is ignored in this version. It is used in the next major version to control whether the rest response should render the total.hits as an object or a number",
+          "default" : false
         }
       }
     },

rest-api-spec/src/main/resources/rest-api-spec/api/search.json

@@ -182,6 +182,11 @@
           "type" : "number",
           "description" : "A threshold that enforces a pre-filter roundtrip to prefilter search shards based on query rewriting if the number of shards the search request expands to exceeds the threshold. This filter roundtrip can limit the number of shards significantly if for instance a shard can not match any documents based on it's rewrite method ie. if date filters are mandatory to match but the shard bounds and the query are disjoint.",
           "default" : 128
+        },
+        "rest_total_hits_as_int" : {
+          "type" : "boolean",
+          "description" : "This parameter is ignored in this version. It is used in the next major version to control whether the rest response should render the total.hits as an object or a number",
+          "default" : false
         }
       }
     },

rest-api-spec/src/main/resources/rest-api-spec/api/search_template.json

@@ -62,6 +62,11 @@
         "typed_keys": {
           "type" : "boolean",
           "description" : "Specify whether aggregation and suggester names should be prefixed by their respective types in the response"
+        },
+        "rest_total_hits_as_int" : {
+          "type" : "boolean",
+          "description" : "This parameter is ignored in this version. It is used in the next major version to control whether the rest response should render the total.hits as an object or a number",
+          "default" : false
         }
       }
     },

rest-api-spec/src/main/resources/rest-api-spec/test/msearch/10_basic.yml

@@ -96,3 +96,28 @@ setup:
   - match:  { responses.3.error.root_cause.0.reason: "/no.such.index/" }
   - match:  { responses.3.error.root_cause.0.index: index_3 }
   - match:  { responses.4.hits.total:     4  }
+
+---
+"Search with rest_total_hits_as_int":
+  - skip:
+      version: " - 6.5.99"
+      reason: rest_total_hits_as_int was introduced in 6.6.0
+
+  - do:
+      msearch:
+        rest_total_hits_as_int: true
+        body:
+          - index: index_*
+          - query:
+              match: {foo: foo}
+          - index: index_2
+          - query:
+              match_all: {}
+          - index: index_1
+          - query:
+              match: {foo: foo}
+
+  - match:  { responses.0.hits.total:     2  }
+  - match:  { responses.1.hits.total:     1  }
+  - match:  { responses.2.hits.total:     1  }
+

rest-api-spec/src/main/resources/rest-api-spec/test/scroll/10_basic.yml

@@ -236,3 +236,66 @@
           query:
             match_all: {}
           size: 0
+
+---
+"Scroll with rest_total_as_int":
+  - skip:
+      version: " - 6.5.99"
+      reason: rest_total_hits_as_int was introduced in 6.6.0
+  - do:
+      indices.create:
+        index: test_scroll
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     42
+        body:   { foo: 1 }
+
+  - do:
+      index:
+        index:  test_scroll
+        type:   test
+        id:     43
+        body:   { foo: 2 }
+
+  - do:
+      indices.refresh: {}
+
+  - do:
+      search:
+        index: test_scroll
+        size: 1
+        scroll: 1m
+        sort: foo
+        rest_total_hits_as_int: true
+        body:
+          query:
+            match_all: {}
+
+  - set: {_scroll_id: scroll_id}
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      1    }
+  - match: {hits.hits.0._id: "42" }
+
+  - do:
+      scroll:
+        rest_total_hits_as_int: true
+        body: { "scroll_id": "$scroll_id", "scroll": "1m"}
+
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      1    }
+  - match: {hits.hits.0._id: "43" }
+
+  - do:
+      scroll:
+        rest_total_hits_as_int: true
+        scroll_id: $scroll_id
+        scroll: 1m
+
+  - match: {hits.total:      2    }
+  - length: {hits.hits:      0    }
+
+  - do:
+      clear_scroll:
+        scroll_id: $scroll_id

rest-api-spec/src/main/resources/rest-api-spec/test/search/20_default_values.yml

@@ -75,3 +75,13 @@ setup:
             match:
               foo: bar
 
+---
+"Search with rest_total_hits_as_int":
+  - skip:
+      version: " - 6.5.99"
+      reason: rest_total_hits_as_int was introduced in 6.6.0
+  - do:
+      search:
+        rest_total_hits_as_int: true
+
+  - match: {hits.total: 2}

server/src/main/java/org/elasticsearch/rest/action/search/RestMultiSearchAction.java

@@ -38,7 +38,9 @@
 import org.elasticsearch.search.builder.SearchSourceBuilder;
 
 import java.io.IOException;
+import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
 
@@ -47,7 +49,14 @@
 
 public class RestMultiSearchAction extends BaseRestHandler {
 
-    private static final Set<String> RESPONSE_PARAMS = Collections.singleton(RestSearchAction.TYPED_KEYS_PARAM);
+    private static final Set<String> RESPONSE_PARAMS;
+
+    static {
+        final Set<String> responseParams = new HashSet<>(
+            Arrays.asList(RestSearchAction.TYPED_KEYS_PARAM, RestSearchAction.TOTAL_HIT_AS_INT_PARAM)
+        );
+        RESPONSE_PARAMS = Collections.unmodifiableSet(responseParams);
+    }
 
     private final boolean allowExplicitIndex;
 

server/src/main/java/org/elasticsearch/rest/action/search/RestSearchAction.java

@@ -43,6 +43,7 @@
 import java.io.IOException;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.HashSet;
 import java.util.Set;
 import java.util.function.IntConsumer;
 
@@ -54,7 +55,13 @@
 public class RestSearchAction extends BaseRestHandler {
 
     public static final String TYPED_KEYS_PARAM = "typed_keys";
-    private static final Set<String> RESPONSE_PARAMS = Collections.singleton(TYPED_KEYS_PARAM);
+    public static final String TOTAL_HIT_AS_INT_PARAM = "rest_total_hits_as_int";
+    private static final Set<String> RESPONSE_PARAMS;
+
+    static {
+        final Set<String> responseParams = new HashSet<>(Arrays.asList(TYPED_KEYS_PARAM, TOTAL_HIT_AS_INT_PARAM));
+        RESPONSE_PARAMS = Collections.unmodifiableSet(responseParams);
+    }
 
     public RestSearchAction(Settings settings, RestController controller) {
         super(settings);

server/src/main/java/org/elasticsearch/rest/action/search/RestSearchScrollAction.java

@@ -29,12 +29,16 @@
 import org.elasticsearch.search.Scroll;
 
 import java.io.IOException;
+import java.util.Collections;
+import java.util.Set;
 
 import static org.elasticsearch.common.unit.TimeValue.parseTimeValue;
 import static org.elasticsearch.rest.RestRequest.Method.GET;
 import static org.elasticsearch.rest.RestRequest.Method.POST;
 
 public class RestSearchScrollAction extends BaseRestHandler {
+    Set<String> RESPONSE_PARAMS = Collections.singleton(RestSearchAction.TOTAL_HIT_AS_INT_PARAM);
+
     public RestSearchScrollAction(Settings settings, RestController controller) {
         super(settings);
 
@@ -70,4 +74,9 @@ public RestChannelConsumer prepareRequest(final RestRequest request, final NodeC
             }});
         return channel -> client.searchScroll(searchScrollRequest, new RestStatusToXContentListener<>(channel));
     }
+
+    @Override
+    protected Set<String> responseParams() {
+        return RESPONSE_PARAMS;
+    }
 }