Note: this will still lead to the UnitOfWork#getSingleIdentifierValue() still being

called when not specifying the type of a DQL parameter being bound via
`Doctrine\ORM\Query#setParameter()`:

```php
$query->setParameter('foo', $theValue, $theType);
```

A full parameter bind is required in order to gain back performance:

```php
$query->setParameter('foo', $theValue, $theType);
```

This is up for discussion with patch reviewers.

lib/Doctrine/ORM/AbstractQuery.php

@@ -72,7 +72,7 @@ abstract class AbstractQuery
     /**
      * The parameter map of this query.
      *
-     * @var \Doctrine\Common\Collections\ArrayCollection
+     * @var ArrayCollection|Parameter[]
      */
     protected $parameters;
 
@@ -306,7 +306,7 @@ abstract class AbstractQuery
     /**
      * Get all defined parameters.
      *
-     * @return \Doctrine\Common\Collections\ArrayCollection The defined query parameters.
+     * @return ArrayCollection The defined query parameters.
      */
     public function getParameters()
     {
@@ -336,7 +336,7 @@ abstract class AbstractQuery
     /**
      * Sets a collection of query parameters.
      *
-     * @param \Doctrine\Common\Collections\ArrayCollection|array $parameters
+     * @param ArrayCollection|mixed[] $parameters
      *
      * @return static This query instance.
      */

lib/Doctrine/ORM/Query.php

@@ -19,15 +19,18 @@
 
 namespace Doctrine\ORM;
 
+use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\DBAL\LockMode;
+use Doctrine\ORM\Mapping\ClassMetadata;
 use Doctrine\ORM\Query\Exec\AbstractSqlExecutor;
+use Doctrine\ORM\Query\Parameter;
+use Doctrine\ORM\Query\ParameterTypeInferer;
 use Doctrine\ORM\Query\Parser;
 use Doctrine\ORM\Query\ParserResult;
 use Doctrine\ORM\Query\QueryException;
-use Doctrine\ORM\Mapping\ClassMetadata;
-use Doctrine\ORM\Query\ParameterTypeInferer;
-use Doctrine\Common\Collections\ArrayCollection;
 use Doctrine\ORM\Utility\HierarchyDiscriminatorResolver;
+use function array_keys;
+use function assert;
 
 /**
  * A Query object represents a DQL query.
@@ -387,26 +390,13 @@ final class Query extends AbstractQuery
         $types     = [];
 
         foreach ($this->parameters as $parameter) {
-            $key    = $parameter->getName();
+            $key = $parameter->getName();
-            $value  = $parameter->getValue();
-            $rsm    = $this->getResultSetMapping();
 
             if ( ! isset($paramMappings[$key])) {
                 throw QueryException::unknownParameter($key);
             }
 
-            if (isset($rsm->metadataParameterMapping[$key]) && $value instanceof ClassMetadata) {
+            [$value, $type] = $this->resolveParameterValue($parameter);
-                $value = $value->getMetadataValue($rsm->metadataParameterMapping[$key]);
-            }
-
-            if (isset($rsm->discriminatorParameters[$key]) && $value instanceof ClassMetadata) {
-                $value = array_keys(HierarchyDiscriminatorResolver::resolveDiscriminatorsForClass($value, $this->_em));
-            }
-
-            $value = $this->processParameterValue($value);
-            $type  = ($parameter->getValue() === $value)
-                ? $parameter->getType()
-                : ParameterTypeInferer::inferType($value);
 
             foreach ($paramMappings[$key] as $position) {
                 $types[$position] = $type;
@@ -439,6 +429,38 @@ final class Query extends AbstractQuery
         return [$sqlParams, $types];
     }
 
+    /** @return mixed[] tuple of (value, type) */
+    private function resolveParameterValue(Parameter $parameter) : array
+    {
+        if ($parameter->typeWasSpecified()) {
+            return [$parameter->getValue(), $parameter->getType()];
+        }
+
+        $key           = $parameter->getName();
+        $originalValue = $parameter->getValue();
+        $value         = $originalValue;
+        $rsm           = $this->getResultSetMapping();
+
+        assert($rsm !== null);
+
+        if ($value instanceof ClassMetadata && isset($rsm->metadataParameterMapping[$key])) {
+            $value = $value->getMetadataValue($rsm->metadataParameterMapping[$key]);
+        }
+
+        if ($value instanceof ClassMetadata && isset($rsm->discriminatorParameters[$key])) {
+            $value = array_keys(HierarchyDiscriminatorResolver::resolveDiscriminatorsForClass($value, $this->_em));
+        }
+
+        $processedValue = $this->processParameterValue($value);
+
+        return [
+            $processedValue,
+            $originalValue === $processedValue
+                ? $parameter->getType()
+                : ParameterTypeInferer::inferType($processedValue),
+        ];
+    }
+
     /**
      * Defines a cache driver to be used for caching queries.
      *

lib/Doctrine/ORM/Query/Parameter.php

@@ -19,6 +19,8 @@
 
 namespace Doctrine\ORM\Query;
 
+use function trim;
+
 /**
  * Defines a Query Parameter.
  *
@@ -49,6 +51,13 @@ class Parameter
      */
     private $type;
 
+    /**
+     * Whether the parameter type was explicitly specified or not
+     *
+     * @var bool
+     */
+    private $typeSpecified;
+
     /**
      * Constructor.
      *
@@ -58,7 +67,8 @@ class Parameter
      */
     public function __construct($name, $value, $type = null)
     {
-        $this->name = trim($name, ':');
+        $this->name          = trim($name, ':');
+        $this->typeSpecified = $type !== null;
 
         $this->setValue($value, $type);
     }
@@ -104,4 +114,9 @@ class Parameter
         $this->value = $value;
         $this->type  = $type ?: ParameterTypeInferer::inferType($value);
     }
+
+    public function typeWasSpecified() : bool
+    {
+        return $this->typeSpecified;
+    }
 }

tests/Doctrine/Tests/ORM/QueryBuilderTest.php

@@ -609,8 +609,11 @@ class QueryBuilderTest extends OrmTestCase
             ->setParameter('id', 1);
 
         $parameter = new Parameter('id', 1, ParameterTypeInferer::inferType(1));
+        $inferred  = $qb->getParameter('id');
 
-        $this->assertEquals($parameter, $qb->getParameter('id'));
+        self::assertSame($parameter->getValue(), $inferred->getValue());
+        self::assertSame($parameter->getType(), $inferred->getType());
+        self::assertFalse($inferred->typeWasSpecified());
     }
 
     public function testSetParameters()