Transfer result cache to count query.

src/Tools/Pagination/Paginator.php

@@ -7,6 +7,7 @@
 use ArrayIterator;
 use Countable;
 use Doctrine\Common\Collections\Collection;
+use Doctrine\DBAL\Cache\CacheException;
 use Doctrine\ORM\Internal\SQLResultCasing;
 use Doctrine\ORM\NoResultException;
 use Doctrine\ORM\Query;
@@ -249,6 +250,17 @@ private function getCountQuery(): Query
             $countQuery->setHint(CountWalker::HINT_DISTINCT, true);
         }
 
+        $qcp = $this->query->getQueryCacheProfile();
+        if ($qcp !== null) {
+            try {
+                $countQuery->setResultCacheId($qcp->getCacheKey());
+            } catch (CacheException $cacheException) {
+                // Continue without the cache key if one was not set.
+            }
+
+            $countQuery->setResultCacheLifetime($qcp->getLifetime());
+        }
+
         if ($this->useOutputWalker($countQuery)) {
             $platform = $countQuery->getEntityManager()->getConnection()->getDatabasePlatform(); // law of demeter win
 

tests/Tests/ORM/Tools/Pagination/PaginatorTest.php

@@ -4,6 +4,7 @@
 
 namespace Doctrine\Tests\ORM\Tools\Pagination;
 
+use Doctrine\DBAL\Cache\QueryCacheProfile;
 use Doctrine\DBAL\Connection;
 use Doctrine\DBAL\Driver;
 use Doctrine\DBAL\Result;
@@ -85,6 +86,43 @@ public function testExtraParametersAreStrippedWhenWalkerRemovingOriginalSelectEl
         ], $receivedParams);
     }
 
+    public function testPaginatorCountWillUseCacheFromOriginalQuery(): void
+    {
+        $paramInWhere   = 1;
+        $returnedCounts = [50];
+
+        $this->hydrator->method('hydrateAll')->willReturn([$returnedCounts]);
+
+        $lifetime = 10;
+        $key      = 'the-key';
+
+        $query = new Query($this->em);
+        $query->setDQL(
+            'SELECT u
+            FROM Doctrine\\Tests\\Models\\CMS\\CmsUser u
+            WHERE u.id = :paramInWhere'
+        );
+        $query->setParameters(['paramInWhere' => $paramInWhere]);
+        $query->setMaxResults(1);
+        $query->enableResultCache($lifetime, $key);
+        $queryCacheProfile = $query->getQueryCacheProfile();
+        $paginator         = (new Paginator($query, true))->setUseOutputWalkers(false);
+
+        $resultStub = $this->createStub(Result::class);
+        $this->connection
+            ->method('executeQuery')
+            ->willReturnCallback(static function (string $sql, array $params, array $types, ?QueryCacheProfile $qcp) use ($key, $lifetime, $queryCacheProfile, $resultStub): Result {
+                self::assertNotNull($qcp);
+                self::assertNotSame($queryCacheProfile, $qcp);
+                self::assertSame($lifetime, $qcp->getLifetime());
+                self::assertSame($key, $qcp->getCacheKey());
+
+                return $resultStub;
+            });
+
+        $paginator->count();
+    }
+
     public function testPaginatorNotCaringAboutExtraParametersWithoutOutputWalkers(): void
     {
         $result = $this->getMockBuilder(Result::class)->disableOriginalConstructor()->getMock();