Add support for query string parameters

Per ES docs: search_type, request_cache, and the allow_partial_search_results
should not be in the body. They should be sent as query string parameters. My
understanding is that chewy should act like this:

  $ IssuesIndex.request_cache(true).render
  # good (new)
  $ {:index=>["issues"], :type=>["issue"], :body=>{}, :request_cache=>true}
  # bad (old)
  $ {:index=>["issues"], :type=>["issue"], :body=>{:request_cache=>true}

I believe this resolves issue toptal#586 and part of issue toptal#642.

(https://www.elastic.co/guide/en/elasticsearch/reference/6.4/search-request-body.html#_parameters_4)

lib/chewy/search/parameters.rb

@@ -10,6 +10,7 @@ module Search
     # @see Chewy::Search::Request#parameters
     # @see Chewy::Search::Parameters::Storage
     class Parameters
+      QUERY_STRING_PARAMS = %i[search_type request_cache].freeze
       # Default storage classes warehouse. It is probably possible to
       # add your own classes here if necessary, but I'm not sure it will work.
       #
@@ -101,11 +102,7 @@ def merge!(other)
       #
       # @return [Hash] request body
       def render
-        body = @storages.except(:filter, :query, :none, :function_score, :score_mode).values.inject({}) do |result, storage|
-          result.merge!(storage.render || {})
-        end
-        body.merge!(render_query || {})
-        body.present? ? {body: body} : {}
+        {}.merge(render_body).merge(render_query_string_params)
       end
 
     protected
@@ -126,6 +123,22 @@ def assert_storages(names)
         names
       end
 
+      def render_query_string_params
+        stores = @storages.select { |storage_name, _| QUERY_STRING_PARAMS.include?(storage_name) }
+        stores.values.inject({}) do |result, storage|
+          result.merge!(storage.render || {})
+        end
+      end
+
+      def render_body
+        exceptions = %i[filter query none function_score score_mode] + QUERY_STRING_PARAMS
+        body = @storages.except(*exceptions).values.inject({}) do |result, storage|
+          result.merge!(storage.render || {})
+        end
+        body.merge!(render_query || {})
+        body.present? ? {body: body} : {}
+      end
+
       def render_query
         none = @storages[:none].render
 

spec/chewy/search/parameters_spec.rb

@@ -102,6 +102,16 @@ def storage_object_ids(params)
     specify { expect(subject.render).to eq(body: {from: 10, sort: ['foo']}) }
     specify { expect(described_class.new.render).to eq({}) }
 
+    context do
+      subject { described_class.new(request_cache: true) }
+      specify { expect(subject.render).to eq(request_cache: true) }
+    end
+
+    context do
+      subject { described_class.new(search_type: 'query_then_fetch') }
+      specify { expect(subject.render).to eq(search_type: 'query_then_fetch') }
+    end
+
     context do
       subject { described_class.new(query: {foo: 'bar'}, filter: {moo: 'baz'}) }
       specify { expect(subject.render).to eq(body: {query: {bool: {must: {foo: 'bar'}, filter: {moo: 'baz'}}}}) }

spec/chewy/search/request_spec.rb

@@ -151,13 +151,20 @@
   end
 
   describe '#request_cache' do
-    specify { expect(subject.request_cache(true).render[:body]).to include(request_cache: true) }
-    specify { expect(subject.request_cache(true).request_cache(false).render[:body]).to include(request_cache: false) }
-    specify { expect(subject.request_cache(true).request_cache(nil).render[:body]).to be_blank }
+    specify { expect(subject.request_cache(true).render).to include(request_cache: true) }
+    specify { expect(subject.request_cache(true).request_cache(false).render).to include(request_cache: false) }
+    specify { expect(subject.request_cache(true).request_cache(nil).render[:request_cache]).to be_blank }
     specify { expect { subject.request_cache(true) }.not_to change { subject.render } }
   end
 
-  %i[search_type preference timeout].each do |name|
+  describe '#search_type' do
+    specify { expect(subject.search_type('foo').render).to include(search_type: 'foo') }
+    specify { expect(subject.search_type('foo').search_type('bar').render).to include(search_type: 'bar') }
+    specify { expect(subject.search_type('foo').search_type(nil).render[:search_type]).to be_blank }
+    specify { expect { subject.search_type('foo') }.not_to change { subject.render } }
+  end
+
+  %i[preference timeout].each do |name|
     describe "##{name}" do
       specify { expect(subject.send(name, :foo).render[:body]).to include(name => 'foo') }
       specify { expect(subject.send(name, :foo).send(name, :bar).render[:body]).to include(name => 'bar') }