Resolve Issue : Search REST API returns wrong total_count

lib/internal/Magento/Framework/Search/Adapter/Mysql/Adapter.php

@@ -7,6 +7,7 @@
 
 use Magento\Framework\App\ResourceConnection;
 use Magento\Framework\DB\Ddl\Table;
+use Magento\Framework\DB\Select;
 use Magento\Framework\Search\Adapter\Mysql\Aggregation\Builder as AggregationBuilder;
 use Magento\Framework\Search\AdapterInterface;
 use Magento\Framework\Search\RequestInterface;
@@ -49,6 +50,16 @@ class Adapter implements AdapterInterface
      */
     private $temporaryStorageFactory;
 
+    /**
+     * Query Select Parts to be skipped when prepare query for count
+     *
+     * @var array
+     */
+    private $countSqlSkipParts = [
+        \Magento\Framework\DB\Select::LIMIT_COUNT => true,
+        \Magento\Framework\DB\Select::LIMIT_OFFSET => true,
+    ];
+
     /**
      * @param Mapper $mapper
      * @param ResponseFactory $responseFactory
@@ -86,7 +97,7 @@ public function query(RequestInterface $request)
         $response = [
             'documents' => $documents,
             'aggregations' => $aggregations,
-            'total' => count($documents)
+            'total' => $this->getSize($query)
         ];
         return $this->responseFactory->create($response);
     }
@@ -115,4 +126,39 @@ private function getConnection()
     {
         return $this->resource->getConnection();
     }
+
+    /**
+     * Get rows size
+     *
+     * @param Select $query
+     * @return int
+     */
+    private function getSize(Select $query): int
+    {
+        $sql = $this->getSelectCountSql($query);
+        $parentSelect = $this->getConnection()->select();
+        $parentSelect->from(['core_select' => $sql]);
+        $parentSelect->reset(\Magento\Framework\DB\Select::COLUMNS);
+        $parentSelect->columns('COUNT(*)');
+        $totalRecords = $this->getConnection()->fetchOne($parentSelect);
+
+        return intval($totalRecords);
+    }
+
+    /**
+     * Reset limit and offset
+     *
+     * @param Select $query
+     * @return Select
+     */
+    private function getSelectCountSql(Select $query): Select
+    {
+        foreach ($this->countSqlSkipParts as $part => $toSkip) {
+            if ($toSkip) {
+                $query->reset($part);
+            }
+        }
+
+        return $query;
+    }
 }

lib/internal/Magento/Framework/Search/Test/Unit/Adapter/Mysql/AdapterTest.php

@@ -161,10 +161,16 @@ public function testQuery()
         $select = $this->getMockBuilder(\Magento\Framework\DB\Select::class)
             ->disableOriginalConstructor()
             ->getMock();
-        $this->connectionAdapter->expects($this->once())
+
+        $this->connectionAdapter->expects($this->exactly(2))
             ->method('select')
             ->willReturn($select);
 
+        $this->connectionAdapter->expects($this->once())
+            ->method('fetchOne')
+            ->with($select)
+            ->willReturn($selectResult['total']);
+
         $table = $this->getMockBuilder(\Magento\Framework\DB\Ddl\Table::class)
             ->disableOriginalConstructor()
             ->getMock();