[STORE] Removed the search_type=scan in the find_in_batches method

Since the `search_type` parameter has been deprecated in Elasticsearch 2
and removed in Elasticsearch 5, the `find_in_batches` method has been
updated to stop using the parameter, and to use the new way of setting
up search context for scrolling with the `sort:_doc` option.

See: https://www.elastic.co/guide/en/elasticsearch/reference/2.1/breaking_21_search_changes.html#_literal_search_type_scan_literal_deprecated

Author: karmi

elasticsearch-persistence/README.md

@@ -581,7 +581,7 @@ retrieve big collections of model instances, using the Elasticsearch's _Scan API
 
 ```ruby
 Article.find_each(_source_include: 'title') { |a| puts "===> #{a.title.upcase}" }
-# GET http://localhost:9200/articles/article/_search?scroll=5m&search_type=scan&size=20
+# GET http://localhost:9200/articles/article/_search?scroll=5m&size=20
 # GET http://localhost:9200/_search/scroll?scroll=5m&scroll_id=c2Nhb...
 # ===> TEST
 # GET http://localhost:9200/_search/scroll?scroll=5m&scroll_id=c2Nhb...

elasticsearch-persistence/lib/elasticsearch/persistence/model/find.rb

@@ -55,7 +55,7 @@ def count(query_or_definition=nil, options={})
             gateway.count( query_or_definition, options )
           end
 
-          # Returns all models efficiently via the Elasticsearch's scan/scroll API
+          # Returns all models efficiently via the Elasticsearch's scroll API
           #
           # You can restrict the models being returned with a query.
           #
@@ -117,20 +117,17 @@ def find_in_batches(options={}, &block)
 
             body = options
 
-            # Get the initial scroll_id
+            # Get the initial batch of documents and the scroll_id
             #
             response = gateway.client.search( { index: gateway.index_name,
                                          type:  gateway.document_type,
-                                         search_type: 'scan',
-                                         scroll:      scroll,
-                                         size:        20,
-                                         body:        body }.merge(search_params) )
+                                         scroll: scroll,
+                                         sort:   ['_doc'],
+                                         size:   20,
+                                         body:   body }.merge(search_params) )
 
-            # Get the initial batch of documents
-            #
-            response = gateway.client.scroll( { scroll_id: response['_scroll_id'], scroll: scroll } )
 
-            # Break when receiving an empty array of hits
+            # Scroll the search object and break when receiving an empty array of hits
             #
             while response['hits']['hits'].any? do
               yield Repository::Response::Results.new(gateway, response)
@@ -149,7 +146,7 @@ def find_in_batches(options={}, &block)
           #
           #     Person.find_each { |person| puts person.name }
           #
-          #     # # GET http://localhost:9200/people/person/_search?scroll=5m&search_type=scan&size=20
+          #     # # GET http://localhost:9200/people/person/_search?scroll=5m&size=20
           #     # # GET http://localhost:9200/_search/scroll?scroll=5m&scroll_id=c2Nhbj...
           #     # Test 0
           #     # Test 1

elasticsearch-persistence/test/unit/model_find_test.rb

@@ -83,27 +83,29 @@ class DummyFindModel
       DummyFindModel.all( { query: { match: { title: 'test' } } }, { routing: 'abc123' } )
     end
 
-    context "finding via scan/scroll" do
+    context "finding via scroll" do
       setup do
         @gateway
         .expects(:deserialize)
-        .with('_source' => {'foo' => 'bar'})
         .returns('_source' => {'foo' => 'bar'})
+        .at_least_once
 
+        # 1. Initial batch of documents and the scroll_id
         @gateway.client
           .expects(:search)
           .with do |arguments|
-            assert_equal 'scan', arguments[:search_type]
             assert_equal 'foo',  arguments[:index]
             assert_equal 'bar',  arguments[:type]
             true
           end
-          .returns(MultiJson.load('{"_scroll_id":"abc123==", "hits":{"hits":[]}}'))
+          .returns(MultiJson.load('{"_scroll_id":"abc123==", "hits":{"hits":[{"_source":{"foo":"bar_1"}}]}}'))
 
+        # 2. Second batch of documents and the scroll_id
+        # 3. Last, empty batch of documents
         @gateway.client
           .expects(:scroll)
           .twice
-          .returns(MultiJson.load('{"_scroll_id":"abc456==", "hits":{"hits":[{"_source":{"foo":"bar"}}]}}'))
+          .returns(MultiJson.load('{"_scroll_id":"abc456==", "hits":{"hits":[{"_source":{"foo":"bar_2"}}]}}'))
           .then
           .returns(MultiJson.load('{"_scroll_id":"abc789==", "hits":{"hits":[]}}'))
       end