diff --git a/.travis.yml b/.travis.yml
index e88053559..57b2cb1f6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,6 +20,7 @@ before_script:
   - if [ "$DEPENDENCIES" != "low" ]; then composer update; fi;
   - if [ "$DEPENDENCIES" == "low" ]; then composer update --prefer-lowest; fi;
   - if [[ $PHPSTAN = 1 ]]; then composer require --dev --prefer-stable phpstan/phpstan:^0.7 symfony/console:^3.0; fi
+  - if [ "$MYSQL_VERSION" == "5.7" ]; then bash ./tests/travis/install-mysql-5.7.sh; fi;
   - if [[ $DB == "mysql" || $DB == "mariadb" ]]; then mysql -e "CREATE SCHEMA doctrine_tests; GRANT ALL PRIVILEGES ON doctrine_tests.* to travis@'%'"; fi;
 
 script:
@@ -47,6 +48,13 @@ matrix:
         - DB=pgsql
         - PHPSTAN=1
 
+    - php: 7.1
+      env: DB=mysql MYSQL_VERSION=5.7
+      sudo: required
+    - php: nightly
+      env: DB=mysql MYSQL_VERSION=5.7
+      sudo: required
+
   allow_failures:
     - php: nightly
 
diff --git a/composer.json b/composer.json
index a4b43de3b..d320b0b4d 100644
--- a/composer.json
+++ b/composer.json
@@ -18,7 +18,7 @@
         "ext-pdo": "*",
         "doctrine/collections": "^1.4",
         "doctrine/dbal": ">=2.5-dev,<2.7-dev",
-        "doctrine/instantiator": "~1.0.1",
+        "doctrine/instantiator": "~1.1",
         "doctrine/common": "^2.7.1",
         "doctrine/cache": "~1.6",
         "doctrine/annotations": "~1.4",
diff --git a/lib/Doctrine/ORM/Tools/Pagination/LimitSubqueryOutputWalker.php b/lib/Doctrine/ORM/Tools/Pagination/LimitSubqueryOutputWalker.php
index 5d59722ed..034b33b2c 100644
--- a/lib/Doctrine/ORM/Tools/Pagination/LimitSubqueryOutputWalker.php
+++ b/lib/Doctrine/ORM/Tools/Pagination/LimitSubqueryOutputWalker.php
@@ -43,6 +43,8 @@ use Doctrine\ORM\Query\AST\SelectStatement;
  */
 class LimitSubqueryOutputWalker extends SqlWalker
 {
+    private const ORDER_BY_PATH_EXPRESSION = '/(?<![a-z0-9_])%s\.%s(?![a-z0-9_])/i';
+
     /**
      * @var \Doctrine\DBAL\Platforms\AbstractPlatform
      */
@@ -354,69 +356,95 @@ class LimitSubqueryOutputWalker extends SqlWalker
     /**
      * Generates new SQL for statements with an order by clause
      *
-     * @param array           $sqlIdentifier
-     * @param string          $innerSql
-     * @param string          $sql
-     * @param OrderByClause   $orderByClause
+     * @param array              $sqlIdentifier
+     * @param string             $innerSql
+     * @param string             $sql
+     * @param OrderByClause|null $orderByClause
      *
      * @return string
      */
-    private function preserveSqlOrdering(array $sqlIdentifier, $innerSql, $sql, $orderByClause)
-    {
-        // If the sql statement has an order by clause, we need to wrap it in a new select distinct
-        // statement
-        if (! $orderByClause instanceof OrderByClause) {
+    private function preserveSqlOrdering(
+        array $sqlIdentifier,
+        string $innerSql,
+        string $sql,
+        ?OrderByClause $orderByClause
+    ) : string {
+        // If the sql statement has an order by clause, we need to wrap it in a new select distinct statement
+        if (! $orderByClause) {
             return $sql;
         }
 
-        // Rebuild the order by clause to work in the scope of the new select statement
-        /* @var array $orderBy an array of rebuilt order by items */
-        $orderBy = $this->rebuildOrderByClauseForOuterScope($orderByClause);
-
-        // Build the select distinct statement
-        $sql = sprintf(
-            'SELECT DISTINCT %s FROM (%s) dctrn_result ORDER BY %s',
-            implode(', ', $sqlIdentifier),
-            $innerSql,
-            implode(', ', $orderBy)
+        // now only select distinct identifier
+        return \sprintf(
+            'SELECT DISTINCT %s FROM (%s) dctrn_result',
+            \implode(', ', $sqlIdentifier),
+            $this->recreateInnerSql($orderByClause, $sqlIdentifier, $innerSql)
         );
-
-        return $sql;
     }
 
     /**
-     * Generates a new order by clause that works in the scope of a select query wrapping the original
+     * Generates a new SQL statement for the inner query to keep the correct sorting
      *
      * @param OrderByClause $orderByClause
-     * @return array
+     * @param array         $identifiers
+     * @param string        $innerSql
+     *
+     * @return string
      */
-    private function rebuildOrderByClauseForOuterScope(OrderByClause $orderByClause)
-    {
-        $dqlAliasToSqlTableAliasMap
-            = $searchPatterns
-            = $replacements
-            = $dqlAliasToClassMap
-            = $selectListAdditions
-            = $orderByItems
-            = [];
+    private function recreateInnerSql(
+        OrderByClause $orderByClause,
+        array $identifiers,
+        string $innerSql
+    ) : string {
+        [$searchPatterns, $replacements] = $this->generateSqlAliasReplacements();
 
-        // Generate DQL alias -> SQL table alias mapping
-        foreach(array_keys($this->rsm->aliasMap) as $dqlAlias) {
-            $dqlAliasToClassMap[$dqlAlias] = $class = $this->queryComponents[$dqlAlias]['metadata'];
-            $dqlAliasToSqlTableAliasMap[$dqlAlias] = $this->getSQLTableAlias($class->getTableName(), $dqlAlias);
+        $orderByItems = [];
+
+        foreach ($orderByClause->orderByItems as $orderByItem) {
+            // Walk order by item to get string representation of it and
+            // replace path expressions in the order by clause with their column alias
+            $orderByItemString = \preg_replace(
+                $searchPatterns,
+                $replacements,
+                $this->walkOrderByItem($orderByItem)
+            );
+
+            $orderByItems[] = $orderByItemString;
+            $identifier     = \substr($orderByItemString, 0, \strrpos($orderByItemString, ' '));
+
+            if (! \in_array($identifier, $identifiers, true)) {
+                $identifiers[] = $identifier;
+            }
         }
 
-        // Pattern to find table path expressions in the order by clause
-        $fieldSearchPattern = '/(?<![a-z0-9_])%s\.%s(?![a-z0-9_])/i';
+        return $sql = \sprintf(
+            'SELECT DISTINCT %s FROM (%s) dctrn_result_inner ORDER BY %s',
+            \implode(', ', $identifiers),
+            $innerSql,
+            \implode(', ', $orderByItems)
+        );
+    }
+
+    /**
+     * @return string[][]
+     */
+    private function generateSqlAliasReplacements() : array
+    {
+        $aliasMap = $searchPatterns = $replacements = $metadataList = [];
+
+        // Generate DQL alias -> SQL table alias mapping
+        foreach (\array_keys($this->rsm->aliasMap) as $dqlAlias) {
+            $metadataList[$dqlAlias] = $class = $this->queryComponents[$dqlAlias]['metadata'];
+            $aliasMap[$dqlAlias] = $this->getSQLTableAlias($class->getTableName(), $dqlAlias);
+        }
 
         // Generate search patterns for each field's path expression in the order by clause
-        foreach($this->rsm->fieldMappings as $fieldAlias => $fieldName) {
+        foreach ($this->rsm->fieldMappings as $fieldAlias => $fieldName) {
             $dqlAliasForFieldAlias = $this->rsm->columnOwnerMap[$fieldAlias];
-            $class = $dqlAliasToClassMap[$dqlAliasForFieldAlias];
+            $class = $metadataList[$dqlAliasForFieldAlias];
 
-            // If the field is from a joined child table, we won't be ordering
-            // on it.
-            if (!isset($class->fieldMappings[$fieldName])) {
+            // If the field is from a joined child table, we won't be ordering on it.
+            if (! isset($class->fieldMappings[$fieldName])) {
                 continue;
             }
 
@@ -425,37 +453,29 @@ class LimitSubqueryOutputWalker extends SqlWalker
             // Get the proper column name as will appear in the select list
             $columnName = $this->quoteStrategy->getColumnName(
                 $fieldName,
-                $dqlAliasToClassMap[$dqlAliasForFieldAlias],
+                $metadataList[$dqlAliasForFieldAlias],
                 $this->em->getConnection()->getDatabasePlatform()
             );
 
             // Get the SQL table alias for the entity and field
-            $sqlTableAliasForFieldAlias = $dqlAliasToSqlTableAliasMap[$dqlAliasForFieldAlias];
+            $sqlTableAliasForFieldAlias = $aliasMap[$dqlAliasForFieldAlias];
+
             if (isset($fieldMapping['declared']) && $fieldMapping['declared'] !== $class->name) {
                 // Field was declared in a parent class, so we need to get the proper SQL table alias
                 // for the joined parent table.
                 $otherClassMetadata = $this->em->getClassMetadata($fieldMapping['declared']);
-                if (!$otherClassMetadata->isMappedSuperclass) {
+
+                if (! $otherClassMetadata->isMappedSuperclass) {
                     $sqlTableAliasForFieldAlias = $this->getSQLTableAlias($otherClassMetadata->getTableName(), $dqlAliasForFieldAlias);
                 }
             }
 
-            // Compose search/replace patterns
-            $searchPatterns[] = sprintf($fieldSearchPattern, $sqlTableAliasForFieldAlias, $columnName);
-            $replacements[] = $fieldAlias;
+            // Compose search and replace patterns
+            $searchPatterns[] = \sprintf(self::ORDER_BY_PATH_EXPRESSION, $sqlTableAliasForFieldAlias, $columnName);
+            $replacements[]   = $fieldAlias;
         }
 
-        foreach($orderByClause->orderByItems as $orderByItem) {
-            // Walk order by item to get string representation of it
-            $orderByItemString = $this->walkOrderByItem($orderByItem);
-
-            // Replace path expressions in the order by clause with their column alias
-            $orderByItemString = preg_replace($searchPatterns, $replacements, $orderByItemString);
-
-            $orderByItems[] = $orderByItemString;
-        }
-
-        return $orderByItems;
+        return [$searchPatterns, $replacements];
     }
 
     /**
diff --git a/tests/Doctrine/Tests/ORM/Tools/Pagination/LimitSubqueryOutputWalkerTest.php b/tests/Doctrine/Tests/ORM/Tools/Pagination/LimitSubqueryOutputWalkerTest.php
index 7e65ab7bc..39ee1360d 100644
--- a/tests/Doctrine/Tests/ORM/Tools/Pagination/LimitSubqueryOutputWalkerTest.php
+++ b/tests/Doctrine/Tests/ORM/Tools/Pagination/LimitSubqueryOutputWalkerTest.php
@@ -8,9 +8,9 @@ use Doctrine\DBAL\Platforms\PostgreSqlPlatform;
 use Doctrine\ORM\Query;
 use Doctrine\ORM\Tools\Pagination\LimitSubqueryOutputWalker;
 
-class LimitSubqueryOutputWalkerTest extends PaginationTestCase
+final class LimitSubqueryOutputWalkerTest extends PaginationTestCase
 {
-    public function testLimitSubquery()
+    public function testLimitSubquery() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT p, c, a FROM Doctrine\Tests\ORM\Tools\Pagination\MyBlogPost p JOIN p.category c JOIN p.author a');
@@ -18,12 +18,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_0 FROM (SELECT m0_.id AS id_0, m0_.title AS title_1, c1_.id AS id_2, a2_.id AS id_3, a2_.name AS name_4, m0_.author_id AS author_id_5, m0_.category_id AS category_id_6 FROM MyBlogPost m0_ INNER JOIN Category c1_ ON m0_.category_id = c1_.id INNER JOIN Author a2_ ON m0_.author_id = a2_.id) dctrn_result", $limitQuery->getSQL()
         );
     }
 
-    public function testLimitSubqueryWithSortPg()
+    public function testLimitSubqueryWithSortPg() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform);
@@ -33,14 +33,14 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_0, MIN(sclr_5) AS dctrn_minrownum FROM (SELECT m0_.id AS id_0, m0_.title AS title_1, c1_.id AS id_2, a2_.id AS id_3, a2_.name AS name_4, ROW_NUMBER() OVER(ORDER BY m0_.title ASC) AS sclr_5, m0_.author_id AS author_id_6, m0_.category_id AS category_id_7 FROM MyBlogPost m0_ INNER JOIN Category c1_ ON m0_.category_id = c1_.id INNER JOIN Author a2_ ON m0_.author_id = a2_.id) dctrn_result GROUP BY id_0 ORDER BY dctrn_minrownum ASC", $limitQuery->getSQL()
         );
 
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithScalarSortPg()
+    public function testLimitSubqueryWithScalarSortPg() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform);
@@ -51,7 +51,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_1, MIN(sclr_3) AS dctrn_minrownum FROM (SELECT COUNT(g0_.id) AS sclr_0, u1_.id AS id_1, g0_.id AS id_2, ROW_NUMBER() OVER(ORDER BY COUNT(g0_.id) ASC) AS sclr_3 FROM User u1_ INNER JOIN user_group u2_ ON u1_.id = u2_.user_id INNER JOIN groups g0_ ON g0_.id = u2_.group_id) dctrn_result GROUP BY id_1 ORDER BY dctrn_minrownum ASC",
             $limitQuery->getSQL()
         );
@@ -59,7 +59,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithMixedSortPg()
+    public function testLimitSubqueryWithMixedSortPg() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform);
@@ -70,7 +70,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_1, MIN(sclr_3) AS dctrn_minrownum FROM (SELECT COUNT(g0_.id) AS sclr_0, u1_.id AS id_1, g0_.id AS id_2, ROW_NUMBER() OVER(ORDER BY COUNT(g0_.id) ASC, u1_.id DESC) AS sclr_3 FROM User u1_ INNER JOIN user_group u2_ ON u1_.id = u2_.user_id INNER JOIN groups g0_ ON g0_.id = u2_.group_id) dctrn_result GROUP BY id_1 ORDER BY dctrn_minrownum ASC",
             $limitQuery->getSQL()
         );
@@ -78,7 +78,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithHiddenScalarSortPg()
+    public function testLimitSubqueryWithHiddenScalarSortPg() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform);
@@ -89,7 +89,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_1, MIN(sclr_3) AS dctrn_minrownum FROM (SELECT COUNT(g0_.id) AS sclr_0, u1_.id AS id_1, g0_.id AS id_2, ROW_NUMBER() OVER(ORDER BY COUNT(g0_.id) ASC, u1_.id DESC) AS sclr_3 FROM User u1_ INNER JOIN user_group u2_ ON u1_.id = u2_.user_id INNER JOIN groups g0_ ON g0_.id = u2_.group_id) dctrn_result GROUP BY id_1 ORDER BY dctrn_minrownum ASC",
             $limitQuery->getSQL()
         );
@@ -97,7 +97,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryPg()
+    public function testLimitSubqueryPg() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform);
@@ -107,7 +107,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithSortOracle()
+    public function testLimitSubqueryWithSortOracle() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new OraclePlatform);
@@ -118,14 +118,14 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT ID_0, MIN(SCLR_5) AS dctrn_minrownum FROM (SELECT m0_.id AS ID_0, m0_.title AS TITLE_1, c1_.id AS ID_2, a2_.id AS ID_3, a2_.name AS NAME_4, ROW_NUMBER() OVER(ORDER BY m0_.title ASC) AS SCLR_5, m0_.author_id AS AUTHOR_ID_6, m0_.category_id AS CATEGORY_ID_7 FROM MyBlogPost m0_ INNER JOIN Category c1_ ON m0_.category_id = c1_.id INNER JOIN Author a2_ ON m0_.author_id = a2_.id) dctrn_result GROUP BY ID_0 ORDER BY dctrn_minrownum ASC", $limitQuery->getSQL()
         );
 
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithScalarSortOracle()
+    public function testLimitSubqueryWithScalarSortOracle() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new OraclePlatform);
@@ -137,7 +137,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT ID_1, MIN(SCLR_3) AS dctrn_minrownum FROM (SELECT COUNT(g0_.id) AS SCLR_0, u1_.id AS ID_1, g0_.id AS ID_2, ROW_NUMBER() OVER(ORDER BY COUNT(g0_.id) ASC) AS SCLR_3 FROM User u1_ INNER JOIN user_group u2_ ON u1_.id = u2_.user_id INNER JOIN groups g0_ ON g0_.id = u2_.group_id) dctrn_result GROUP BY ID_1 ORDER BY dctrn_minrownum ASC",
             $limitQuery->getSQL()
         );
@@ -145,7 +145,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryWithMixedSortOracle()
+    public function testLimitSubqueryWithMixedSortOracle() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new OraclePlatform);
@@ -157,7 +157,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT ID_1, MIN(SCLR_3) AS dctrn_minrownum FROM (SELECT COUNT(g0_.id) AS SCLR_0, u1_.id AS ID_1, g0_.id AS ID_2, ROW_NUMBER() OVER(ORDER BY COUNT(g0_.id) ASC, u1_.id DESC) AS SCLR_3 FROM User u1_ INNER JOIN user_group u2_ ON u1_.id = u2_.user_id INNER JOIN groups g0_ ON g0_.id = u2_.group_id) dctrn_result GROUP BY ID_1 ORDER BY dctrn_minrownum ASC",
             $limitQuery->getSQL()
         );
@@ -165,7 +165,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testLimitSubqueryOracle()
+    public function testLimitSubqueryOracle() : void
     {
         $odp = $this->entityManager->getConnection()->getDatabasePlatform();
         $this->entityManager->getConnection()->setDatabasePlatform(new OraclePlatform);
@@ -176,21 +176,21 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT ID_0 FROM (SELECT m0_.id AS ID_0, m0_.title AS TITLE_1, c1_.id AS ID_2, a2_.id AS ID_3, a2_.name AS NAME_4, m0_.author_id AS AUTHOR_ID_5, m0_.category_id AS CATEGORY_ID_6 FROM MyBlogPost m0_ INNER JOIN Category c1_ ON m0_.category_id = c1_.id INNER JOIN Author a2_ ON m0_.author_id = a2_.id) dctrn_result", $limitQuery->getSQL()
         );
 
         $this->entityManager->getConnection()->setDatabasePlatform($odp);
     }
 
-    public function testCountQueryMixedResultsWithName()
+    public function testCountQueryMixedResultsWithName() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a, sum(a.name) as foo FROM Doctrine\Tests\ORM\Tools\Pagination\Author a');
         $limitQuery = clone $query;
         $limitQuery->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             "SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, sum(a0_.name) AS sclr_2 FROM Author a0_) dctrn_result", $limitQuery->getSQL()
         );
     }
@@ -198,7 +198,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
     /**
      * @group DDC-3336
      */
-    public function testCountQueryWithArithmeticOrderByCondition()
+    public function testCountQueryWithArithmeticOrderByCondition() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a FROM Doctrine\Tests\ORM\Tools\Pagination\Author a ORDER BY (1 - 1000) * 1 DESC'
@@ -208,12 +208,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
         $this->assertSame(
-            'SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1 FROM Author a0_) dctrn_result ORDER BY (1 - 1000) * 1 DESC',
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, (1 - 1000) * 1 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1 FROM Author a0_) dctrn_result_inner ORDER BY (1 - 1000) * 1 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testCountQueryWithComplexScalarOrderByItem()
+    public function testCountQueryWithComplexScalarOrderByItem() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a FROM Doctrine\Tests\ORM\Tools\Pagination\Avatar a ORDER BY a.image_height * a.image_width DESC'
@@ -223,12 +223,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
         $this->assertSame(
-            'SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.image AS image_1, a0_.image_height AS image_height_2, a0_.image_width AS image_width_3, a0_.image_alt_desc AS image_alt_desc_4, a0_.user_id AS user_id_5 FROM Avatar a0_) dctrn_result ORDER BY image_height_2 * image_width_3 DESC',
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, image_height_2 * image_width_3 FROM (SELECT a0_.id AS id_0, a0_.image AS image_1, a0_.image_height AS image_height_2, a0_.image_width AS image_width_3, a0_.image_alt_desc AS image_alt_desc_4, a0_.user_id AS user_id_5 FROM Avatar a0_) dctrn_result_inner ORDER BY image_height_2 * image_width_3 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testCountQueryWithComplexScalarOrderByItemJoined()
+    public function testCountQueryWithComplexScalarOrderByItemJoined() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT u FROM Doctrine\Tests\ORM\Tools\Pagination\User u JOIN u.avatar a ORDER BY a.image_height * a.image_width DESC'
@@ -238,12 +238,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
         $this->assertSame(
-            'SELECT DISTINCT id_0 FROM (SELECT u0_.id AS id_0, a1_.image_height AS image_height_1, a1_.image_width AS image_width_2, a1_.user_id AS user_id_3 FROM User u0_ INNER JOIN Avatar a1_ ON u0_.id = a1_.user_id) dctrn_result ORDER BY image_height_1 * image_width_2 DESC',
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, image_height_1 * image_width_2 FROM (SELECT u0_.id AS id_0, a1_.image_height AS image_height_1, a1_.image_width AS image_width_2, a1_.user_id AS user_id_3 FROM User u0_ INNER JOIN Avatar a1_ ON u0_.id = a1_.user_id) dctrn_result_inner ORDER BY image_height_1 * image_width_2 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testCountQueryWithComplexScalarOrderByItemJoinedWithPartial()
+    public function testCountQueryWithComplexScalarOrderByItemJoinedWithPartial() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT u, partial a.{id, image_alt_desc} FROM Doctrine\Tests\ORM\Tools\Pagination\User u JOIN u.avatar a ORDER BY a.image_height * a.image_width DESC'
@@ -253,12 +253,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
         $this->assertSame(
-            'SELECT DISTINCT id_0 FROM (SELECT u0_.id AS id_0, a1_.id AS id_1, a1_.image_alt_desc AS image_alt_desc_2, a1_.image_height AS image_height_3, a1_.image_width AS image_width_4, a1_.user_id AS user_id_5 FROM User u0_ INNER JOIN Avatar a1_ ON u0_.id = a1_.user_id) dctrn_result ORDER BY image_height_3 * image_width_4 DESC',
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, image_height_3 * image_width_4 FROM (SELECT u0_.id AS id_0, a1_.id AS id_1, a1_.image_alt_desc AS image_alt_desc_2, a1_.image_height AS image_height_3, a1_.image_width AS image_width_4, a1_.user_id AS user_id_5 FROM User u0_ INNER JOIN Avatar a1_ ON u0_.id = a1_.user_id) dctrn_result_inner ORDER BY image_height_3 * image_width_4 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testCountQueryWithComplexScalarOrderByItemOracle()
+    public function testCountQueryWithComplexScalarOrderByItemOracle() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a FROM Doctrine\Tests\ORM\Tools\Pagination\Avatar a ORDER BY a.image_height * a.image_width DESC'
@@ -276,7 +276,7 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
     /**
      * @group DDC-3434
      */
-    public function testLimitSubqueryWithHiddenSelectionInOrderBy()
+    public function testLimitSubqueryWithHiddenSelectionInOrderBy() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a, a.name AS HIDDEN ord FROM Doctrine\Tests\ORM\Tools\Pagination\Author a ORDER BY ord DESC'
@@ -284,13 +284,13 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
 
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
-            'SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, a0_.name AS name_2 FROM Author a0_) dctrn_result ORDER BY name_2 DESC',
+        self::assertSame(
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, name_2 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, a0_.name AS name_2 FROM Author a0_) dctrn_result_inner ORDER BY name_2 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testLimitSubqueryWithColumnWithSortDirectionInName()
+    public function testLimitSubqueryWithColumnWithSortDirectionInName() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT a FROM Doctrine\Tests\ORM\Tools\Pagination\Avatar a ORDER BY a.image_alt_desc DESC'
@@ -300,12 +300,12 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
         $this->assertSame(
-            'SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.image AS image_1, a0_.image_height AS image_height_2, a0_.image_width AS image_width_3, a0_.image_alt_desc AS image_alt_desc_4, a0_.user_id AS user_id_5 FROM Avatar a0_) dctrn_result ORDER BY image_alt_desc_4 DESC',
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, image_alt_desc_4 FROM (SELECT a0_.id AS id_0, a0_.image AS image_1, a0_.image_height AS image_height_2, a0_.image_width AS image_width_3, a0_.image_alt_desc AS image_alt_desc_4, a0_.user_id AS user_id_5 FROM Avatar a0_) dctrn_result_inner ORDER BY image_alt_desc_4 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testLimitSubqueryWithOrderByInnerJoined()
+    public function testLimitSubqueryWithOrderByInnerJoined() : void
     {
         $query = $this->entityManager->createQuery(
             'SELECT b FROM Doctrine\Tests\ORM\Tools\Pagination\BlogPost b JOIN b.author a ORDER BY a.name ASC'
@@ -313,13 +313,13 @@ class LimitSubqueryOutputWalkerTest extends PaginationTestCase
 
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
-            'SELECT DISTINCT id_0 FROM (SELECT b0_.id AS id_0, a1_.name AS name_1, b0_.author_id AS author_id_2, b0_.category_id AS category_id_3 FROM BlogPost b0_ INNER JOIN Author a1_ ON b0_.author_id = a1_.id) dctrn_result ORDER BY name_1 ASC',
+        self::assertSame(
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, name_1 FROM (SELECT b0_.id AS id_0, a1_.name AS name_1, b0_.author_id AS author_id_2, b0_.category_id AS category_id_3 FROM BlogPost b0_ INNER JOIN Author a1_ ON b0_.author_id = a1_.id) dctrn_result_inner ORDER BY name_1 ASC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testLimitSubqueryWithOrderByAndSubSelectInWhereClauseMySql()
+    public function testLimitSubqueryWithOrderByAndSubSelectInWhereClauseMySql() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new MySqlPlatform());
         $query = $this->entityManager->createQuery(
@@ -329,13 +329,13 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
-            'SELECT DISTINCT id_0 FROM (SELECT b0_.id AS id_0, b0_.author_id AS author_id_1, b0_.category_id AS category_id_2 FROM BlogPost b0_ WHERE ((SELECT COUNT(b1_.id) AS sclr_3 FROM BlogPost b1_) = 1)) dctrn_result ORDER BY id_0 DESC',
+        self::assertSame(
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0 FROM (SELECT b0_.id AS id_0, b0_.author_id AS author_id_1, b0_.category_id AS category_id_2 FROM BlogPost b0_ WHERE ((SELECT COUNT(b1_.id) AS sclr_3 FROM BlogPost b1_) = 1)) dctrn_result_inner ORDER BY id_0 DESC) dctrn_result',
             $query->getSQL()
         );
     }
 
-    public function testLimitSubqueryWithOrderByAndSubSelectInWhereClausePgSql()
+    public function testLimitSubqueryWithOrderByAndSubSelectInWhereClausePgSql() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform());
         $query = $this->entityManager->createQuery(
@@ -345,7 +345,7 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             'SELECT DISTINCT id_0, MIN(sclr_1) AS dctrn_minrownum FROM (SELECT b0_.id AS id_0, ROW_NUMBER() OVER(ORDER BY b0_.id DESC) AS sclr_1, b0_.author_id AS author_id_2, b0_.category_id AS category_id_3 FROM BlogPost b0_ WHERE ((SELECT COUNT(b1_.id) AS sclr_4 FROM BlogPost b1_) = 1)) dctrn_result GROUP BY id_0 ORDER BY dctrn_minrownum ASC',
             $query->getSQL()
         );
@@ -354,7 +354,7 @@ ORDER BY b.id DESC'
     /**
      * This tests ordering by property that has the 'declared' field.
      */
-    public function testLimitSubqueryOrderByFieldFromMappedSuperclass()
+    public function testLimitSubqueryOrderByFieldFromMappedSuperclass() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new MySqlPlatform());
 
@@ -364,8 +364,8 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
-            'SELECT DISTINCT id_0 FROM (SELECT b0_.id AS id_0, b0_.name AS name_1 FROM Banner b0_) dctrn_result ORDER BY id_0 DESC',
+        self::assertSame(
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0 FROM (SELECT b0_.id AS id_0, b0_.name AS name_1 FROM Banner b0_) dctrn_result_inner ORDER BY id_0 DESC) dctrn_result',
             $query->getSQL()
         );
     }
@@ -373,7 +373,7 @@ ORDER BY b.id DESC'
     /**
      * Tests order by on a subselect expression (mysql).
      */
-    public function testLimitSubqueryOrderBySubSelectOrderByExpression()
+    public function testLimitSubqueryOrderBySubSelectOrderByExpression() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new MySqlPlatform());
 
@@ -389,8 +389,8 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
-            'SELECT DISTINCT id_0 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, (SELECT MIN(m1_.title) AS sclr_3 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) AS sclr_2 FROM Author a0_) dctrn_result ORDER BY sclr_2 DESC',
+        self::assertSame(
+            'SELECT DISTINCT id_0 FROM (SELECT DISTINCT id_0, sclr_2 FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, (SELECT MIN(m1_.title) AS sclr_3 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) AS sclr_2 FROM Author a0_) dctrn_result_inner ORDER BY sclr_2 DESC) dctrn_result',
             $query->getSQL()
         );
     }
@@ -398,7 +398,7 @@ ORDER BY b.id DESC'
     /**
      * Tests order by on a subselect expression invoking RowNumberOverFunction (postgres).
      */
-    public function testLimitSubqueryOrderBySubSelectOrderByExpressionPg()
+    public function testLimitSubqueryOrderBySubSelectOrderByExpressionPg() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new PostgreSqlPlatform());
 
@@ -414,7 +414,7 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             'SELECT DISTINCT id_0, MIN(sclr_4) AS dctrn_minrownum FROM (SELECT a0_.id AS id_0, a0_.name AS name_1, (SELECT MIN(m1_.title) AS sclr_3 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) AS sclr_2, ROW_NUMBER() OVER(ORDER BY (SELECT MIN(m1_.title) AS sclr_5 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) DESC) AS sclr_4 FROM Author a0_) dctrn_result GROUP BY id_0 ORDER BY dctrn_minrownum ASC',
             $query->getSQL()
         );
@@ -423,7 +423,7 @@ ORDER BY b.id DESC'
     /**
      * Tests order by on a subselect expression invoking RowNumberOverFunction (oracle).
      */
-    public function testLimitSubqueryOrderBySubSelectOrderByExpressionOracle()
+    public function testLimitSubqueryOrderBySubSelectOrderByExpressionOracle() : void
     {
         $this->entityManager->getConnection()->setDatabasePlatform(new OraclePlatform());
 
@@ -439,7 +439,7 @@ ORDER BY b.id DESC'
         );
         $query->setHint(Query::HINT_CUSTOM_OUTPUT_WALKER, LimitSubqueryOutputWalker::class);
 
-        $this->assertEquals(
+        self::assertSame(
             'SELECT DISTINCT ID_0, MIN(SCLR_4) AS dctrn_minrownum FROM (SELECT a0_.id AS ID_0, a0_.name AS NAME_1, (SELECT MIN(m1_.title) AS SCLR_3 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) AS SCLR_2, ROW_NUMBER() OVER(ORDER BY (SELECT MIN(m1_.title) AS SCLR_5 FROM MyBlogPost m1_ WHERE m1_.author_id = a0_.id) DESC) AS SCLR_4 FROM Author a0_) dctrn_result GROUP BY ID_0 ORDER BY dctrn_minrownum ASC',
             $query->getSQL()
         );
diff --git a/tests/travis/install-mysql-5.7.sh b/tests/travis/install-mysql-5.7.sh
new file mode 100644
index 000000000..66b0d1ecf
--- /dev/null
+++ b/tests/travis/install-mysql-5.7.sh
@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+
+set -ex
+
+echo "Installing MySQL 5.7..."
+
+sudo service mysql stop
+sudo apt-get remove "^mysql.*"
+sudo apt-get autoremove
+sudo apt-get autoclean
+echo mysql-apt-config mysql-apt-config/select-server select mysql-5.7 | sudo debconf-set-selections
+wget http://dev.mysql.com/get/mysql-apt-config_0.8.6-1_all.deb
+sudo DEBIAN_FRONTEND=noninteractive dpkg -i mysql-apt-config_0.8.6-1_all.deb
+sudo rm -rf /var/lib/apt/lists/*
+sudo apt-get clean
+sudo apt-get update -q
+sudo apt-get install -q -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" mysql-server libmysqlclient-dev
+sudo mysql_upgrade
+
+echo "Restart mysql..."
+sudo mysql -e "use mysql; update user set authentication_string=PASSWORD('') where User='root'; update user set plugin='mysql_native_password';FLUSH PRIVILEGES;"
+