Deprecated platform-specific portability mode constants

UPGRADE.md

 # Upgrade to 2.11
 
+## Deprecated `Portability\Connection::PORTABILITY_{PLATFORM}` constants`
+
+The platform-specific portability mode flags are meant to be used only by the portability layer internally to optimize
+the user-provided mode for the current database platform. 
+
 ## Deprecated `MasterSlaveConnection` use `PrimaryReadReplicaConnection`
 
 The `Doctrine\DBAL\Connections\MasterSlaveConnection` class is renamed to `Doctrine\DBAL\Connections\PrimaryReadReplicaConnection`.

lib/Doctrine/DBAL/Portability/Connection.php

@@ -23,6 +23,10 @@ class Connection extends \Doctrine\DBAL\Connection
     public const PORTABILITY_EMPTY_TO_NULL = 4;
     public const PORTABILITY_FIX_CASE      = 8;
 
+    /**#@+
+     *
+     * @deprecated Will be removed as internal implementation details.
+     */
     public const PORTABILITY_DB2          = 13;
     public const PORTABILITY_ORACLE       = 9;
     public const PORTABILITY_POSTGRESQL   = 13;
@@ -31,6 +35,7 @@ class Connection extends \Doctrine\DBAL\Connection
     public const PORTABILITY_DRIZZLE      = 13;
     public const PORTABILITY_SQLANYWHERE  = 13;
     public const PORTABILITY_SQLSRV       = 13;
+    /**#@-*/
 
     /** @var int */
     private $portability = self::PORTABILITY_NONE;
@@ -47,25 +52,10 @@ class Connection extends \Doctrine\DBAL\Connection
         if ($ret) {
             $params = $this->getParams();
             if (isset($params['portability'])) {
-                if ($this->getDatabasePlatform()->getName() === 'oracle') {
-                    $params['portability'] &= self::PORTABILITY_ORACLE;
-                } elseif ($this->getDatabasePlatform()->getName() === 'postgresql') {
-                    $params['portability'] &= self::PORTABILITY_POSTGRESQL;
-                } elseif ($this->getDatabasePlatform()->getName() === 'sqlite') {
-                    $params['portability'] &= self::PORTABILITY_SQLITE;
-                } elseif ($this->getDatabasePlatform()->getName() === 'drizzle') {
-                    $params['portability'] &= self::PORTABILITY_DRIZZLE;
-                } elseif ($this->getDatabasePlatform()->getName() === 'sqlanywhere') {
-                    $params['portability'] &= self::PORTABILITY_SQLANYWHERE;
-                } elseif ($this->getDatabasePlatform()->getName() === 'db2') {
-                    $params['portability'] &= self::PORTABILITY_DB2;
-                } elseif ($this->getDatabasePlatform()->getName() === 'mssql') {
-                    $params['portability'] &= self::PORTABILITY_SQLSRV;
-                } else {
-                    $params['portability'] &= self::PORTABILITY_OTHERVENDORS;
-                }
-
-                $this->portability = $params['portability'];
+                $this->portability = $params['portability'] = (new OptimizeFlags())(
+                    $this->getDatabasePlatform(),
+                    $params['portability']
+                );
             }
 
             if (isset($params['fetch_case']) && $this->portability & self::PORTABILITY_FIX_CASE) {

lib/Doctrine/DBAL/Portability/OptimizeFlags.php

+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\DBAL\Portability;
+
+use Doctrine\DBAL\Platforms\AbstractPlatform;
+use Doctrine\DBAL\Platforms\DB2Platform;
+use Doctrine\DBAL\Platforms\OraclePlatform;
+use Doctrine\DBAL\Platforms\PostgreSQL94Platform;
+use Doctrine\DBAL\Platforms\SQLAnywhere16Platform;
+use Doctrine\DBAL\Platforms\SqlitePlatform;
+use Doctrine\DBAL\Platforms\SQLServer2012Platform;
+
+final class OptimizeFlags
+{
+    /**
+     * Platform-specific portability flags that need to be excluded from the user-provided mode
+     * since the platform already operates in this mode to avoid unnecessary conversion overhead.
+     *
+     * @var array<string,int>
+     */
+    private static $platforms = [
+        DB2Platform::class           => 0,
+        OraclePlatform::class        => Connection::PORTABILITY_EMPTY_TO_NULL,
+        PostgreSQL94Platform::class  => 0,
+        SQLAnywhere16Platform::class => 0,
+        SqlitePlatform::class        => 0,
+        SQLServer2012Platform::class => 0,
+    ];
+
+    public function __invoke(AbstractPlatform $platform, int $flags): int
+    {
+        foreach (self::$platforms as $class => $mask) {
+            if ($platform instanceof $class) {
+                $flags &= ~$mask;
+
+                break;
+            }
+        }
+
+        return $flags;
+    }
+}

tests/Doctrine/Tests/DBAL/Portability/OptimizeFlagsTest.php

+<?php
+
+declare(strict_types=1);
+
+namespace Doctrine\Tests\DBAL\Portability;
+
+use Doctrine\DBAL\Platforms\OraclePlatform;
+use Doctrine\DBAL\Platforms\SqlitePlatform;
+use Doctrine\DBAL\Portability\Connection;
+use Doctrine\DBAL\Portability\OptimizeFlags;
+use PHPUnit\Framework\TestCase;
+
+class OptimizeFlagsTest extends TestCase
+{
+    /** @var OptimizeFlags */
+    private $optimizeFlags;
+
+    protected function setUp(): void
+    {
+        $this->optimizeFlags = new OptimizeFlags();
+    }
+
+    public function testOracle(): void
+    {
+        $flags = ($this->optimizeFlags)(new OraclePlatform(), Connection::PORTABILITY_ALL);
+
+        self::assertSame(0, $flags & Connection::PORTABILITY_EMPTY_TO_NULL);
+    }
+
+    public function testAnotherPlatform(): void
+    {
+        $flags = ($this->optimizeFlags)(new SqlitePlatform(), Connection::PORTABILITY_ALL);
+
+        self::assertSame(Connection::PORTABILITY_ALL, $flags);
+    }
+}