[Backport 7.x] Use filter_path for improving the search helpers performances (#1201)

test/unit/helpers/search.test.js

@@ -11,6 +11,7 @@ const { connection } = require('../../utils')
 test('Search should have an additional documents property', async t => {
   const MockConnection = connection.buildMockConnection({
     onRequest (params) {
+      t.strictEqual(params.querystring, 'filter_path=hits.hits._source')
       return {
         body: {
           hits: {
@@ -44,6 +45,7 @@ test('Search should have an additional documents property', async t => {
 test('kGetHits fallback', async t => {
   const MockConnection = connection.buildMockConnection({
     onRequest (params) {
+      t.strictEqual(params.querystring, 'filter_path=hits.hits._source')
       return { body: {} }
     }
   })
@@ -59,3 +61,73 @@ test('kGetHits fallback', async t => {
   })
   t.deepEqual(result, [])
 })
+
+test('Merge filter paths (snake_case)', async t => {
+  const MockConnection = connection.buildMockConnection({
+    onRequest (params) {
+      t.strictEqual(params.querystring, 'filter_path=foo%2Chits.hits._source')
+      return {
+        body: {
+          hits: {
+            hits: [
+              { _source: { one: 'one' } },
+              { _source: { two: 'two' } },
+              { _source: { three: 'three' } }
+            ]
+          }
+        }
+      }
+    }
+  })
+
+  const client = new Client({
+    node: 'http://localhost:9200',
+    Connection: MockConnection
+  })
+
+  const result = await client.helpers.search({
+    index: 'test',
+    filter_path: 'foo',
+    body: { foo: 'bar' }
+  })
+  t.deepEqual(result, [
+    { one: 'one' },
+    { two: 'two' },
+    { three: 'three' }
+  ])
+})
+
+test('Merge filter paths (camelCase)', async t => {
+  const MockConnection = connection.buildMockConnection({
+    onRequest (params) {
+      t.strictEqual(params.querystring, 'filter_path=foo%2Chits.hits._source')
+      return {
+        body: {
+          hits: {
+            hits: [
+              { _source: { one: 'one' } },
+              { _source: { two: 'two' } },
+              { _source: { three: 'three' } }
+            ]
+          }
+        }
+      }
+    }
+  })
+
+  const client = new Client({
+    node: 'http://localhost:9200',
+    Connection: MockConnection
+  })
+
+  const result = await client.helpers.search({
+    index: 'test',
+    filterPath: 'foo',
+    body: { foo: 'bar' }
+  })
+  t.deepEqual(result, [
+    { one: 'one' },
+    { two: 'two' },
+    { three: 'three' }
+  ])
+})