Keep track of neccessary scroll pages to skip useless last request (ruflin#1273)

Author: Tobion

CHANGELOG.md

@@ -20,6 +20,7 @@ All notable changes to this project will be documented in this file based on the
 - added support for the "explain" flag of AnalyzeAPI [#1254](https://github.com/ruflin/Elastica/pull/1254)
 - added support for the "request_cache" search option [#1243](https://github.com/ruflin/Elastica/pull/1243)
 - skip sending "retry_on_conflict=0" default query param to improve compatibility with Amazon Elasticsearch [#1047](https://github.com/ruflin/Elastica/pull/1047)
+- optimized `\Elastica\Scroll` to avoid one request [#1273](https://github.com/ruflin/Elastica/pull/1273)
 
 ### Deprecated
 

lib/Elastica/Scroll.php

@@ -32,12 +32,14 @@ class Scroll implements \Iterator
 
     /**
      * 0: scroll<br>
-     * 1: scroll id<br>
-     * 2: search type.
+     * 1: scroll id
      *
      * @var array
      */
-    protected $_options = [null, null, null];
+    protected $_options = [null, null];
+
+    private $totalPages = 0;
+    private $currentPage = 0;
 
     /**
      * Constructor.
@@ -70,13 +72,21 @@ public function current()
      */
     public function next()
     {
-        $this->_saveOptions();
+        if ($this->currentPage < $this->totalPages) {
+            $this->_saveOptions();
 
-        $this->_search->setOption(Search::OPTION_SCROLL, $this->expiryTime);
-        $this->_search->setOption(Search::OPTION_SCROLL_ID, $this->_nextScrollId);
-        $this->_setScrollId($this->_search->search());
+            $this->_search->setOption(Search::OPTION_SCROLL, $this->expiryTime);
+            $this->_search->setOption(Search::OPTION_SCROLL_ID, $this->_nextScrollId);
 
-        $this->_revertOptions();
+            $this->_setScrollId($this->_search->search());
+
+            $this->_revertOptions();
+        } else {
+            // If there are no pages left, we do not need to query ES.
+            // Reset scroll ID so valid() returns false.
+            $this->_nextScrollId = null;
+            $this->_currentResultSet = null;
+        }
     }
 
     /**
@@ -100,10 +110,7 @@ public function key()
      */
     public function valid()
     {
-        return
-            $this->_nextScrollId !== null
-            && $this->_currentResultSet !== null
-            && $this->_currentResultSet->count() > 0;
+        return $this->_nextScrollId !== null;
     }
 
     /**
@@ -114,8 +121,8 @@ public function valid()
     public function rewind()
     {
         // reset state
-        $this->_nextScrollId = null;
-        $this->_options = [null, null, null];
+        $this->_options = [null, null];
+        $this->currentPage = 0;
 
         // initial search
         $this->_saveOptions();
@@ -135,11 +142,9 @@ public function rewind()
     protected function _setScrollId(ResultSet $resultSet)
     {
         $this->_currentResultSet = $resultSet;
-
-        $this->_nextScrollId = null;
-        if ($resultSet->getResponse()->isOk()) {
-            $this->_nextScrollId = $resultSet->getResponse()->getScrollId();
-        }
+        $this->currentPage++;
+        $this->totalPages = $resultSet->count() > 0 ? ceil($resultSet->getTotalHits() / $resultSet->count()) : 0;
+        $this->_nextScrollId = $resultSet->getResponse()->isOk() ? $resultSet->getResponse()->getScrollId() : null;
     }
 
     /**