diff --git a/core/core.services.yml b/core/core.services.yml
index e2939e9..a8fe133 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -763,6 +763,9 @@ services:
     arguments: ['@database']
     tags:
       - { name: backend_overridable }
+  pgsql.entity.query.sql:
+    class: Drupal\Core\Entity\Query\Sql\pgsql\QueryFactory
+    arguments: ['@database']
   entity.query.null:
     class: Drupal\Core\Entity\Query\Null\QueryFactory
   entity.query.keyvalue:
diff --git a/core/lib/Drupal/Core/Database/Driver/mysql/EntityQuery/Condition.php b/core/lib/Drupal/Core/Database/Driver/mysql/EntityQuery/Condition.php
deleted file mode 100644
index 9f58021..0000000
--- a/core/lib/Drupal/Core/Database/Driver/mysql/EntityQuery/Condition.php
+++ /dev/null
@@ -1,22 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains Drupal\Core\Database\Driver\mysql\EntityQuery\Condition
- */
-
-namespace Drupal\Core\Database\Driver\mysql\EntityQuery;
-
-use Drupal\Core\Database\EntityQuery\ConditionInterface as EntityQueryConditionInterface;
-
-/**
- * Implements entity query conditions for SQL databases.
- */
-class Condition implements EntityQueryConditionInterface {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function translateCondition(array &$condition, $case_sensitive) { }
-
-}
diff --git a/core/lib/Drupal/Core/Database/Driver/pgsql/EntityQuery/Condition.php b/core/lib/Drupal/Core/Database/Driver/pgsql/EntityQuery/Condition.php
deleted file mode 100644
index d820fb1..0000000
--- a/core/lib/Drupal/Core/Database/Driver/pgsql/EntityQuery/Condition.php
+++ /dev/null
@@ -1,44 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains Drupal\Core\Database\Driver\pgsql\EntityQuery\Condition
- */
-
-namespace Drupal\Core\Database\Driver\pgsql\EntityQuery;
-
-use Drupal\Core\Database\Database;
-use Drupal\Core\Database\EntityQuery\ConditionInterface as EntityQueryConditionInterface;
-
-/**
- * Implements entity query conditions for SQL databases.
- */
-class Condition implements EntityQueryConditionInterface {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function translateCondition(array &$condition, $case_sensitive) {
-    $connection = Database::getConnection();
-
-    // For PostgreSQL all the condition arguments need to have case
-    // lowered to support not case sensitive fields.
-    if (is_array($condition['value']) && $case_sensitive === FALSE) {
-      $condition['where'] = 'LOWER(' . $connection->escapeField($condition['real_field']) . ') ' . $condition['operator'] . ' (';
-      $condition['where_args'] = [];
-
-      $n = 1;
-      // Only use the array values in case an associative array is passed as an
-      // argument following similar pattern in
-      // \Drupal\Core\Database\Connection::expandArguments().
-      foreach ($condition['value'] as $value) {
-        $condition['where'] .= 'LOWER(:value' . $n . '),';
-        $condition['where_args'][':value' . $n] = $value;
-        $n++;
-      }
-      $condition['where'] = trim($condition['where'], ',');
-      $condition['where'] .= ')';
-    }
-  }
-
-}
diff --git a/core/lib/Drupal/Core/Database/Driver/sqlite/EntityQuery/Condition.php b/core/lib/Drupal/Core/Database/Driver/sqlite/EntityQuery/Condition.php
deleted file mode 100644
index e59eb05..0000000
--- a/core/lib/Drupal/Core/Database/Driver/sqlite/EntityQuery/Condition.php
+++ /dev/null
@@ -1,22 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains Drupal\Core\Database\Driver\sqlite\EntityQuery\Condition
- */
-
-namespace Drupal\Core\Database\Driver\sqlite\EntityQuery;
-
-use Drupal\Core\Database\EntityQuery\ConditionInterface as EntityQueryConditionInterface;
-
-/**
- * Implements entity query conditions for SQL databases.
- */
-class Condition implements EntityQueryConditionInterface {
-
-  /**
-   * {@inheritdoc}
-   */
-  public static function translateCondition(array &$condition, $case_sensitive) { }
-
-}
diff --git a/core/lib/Drupal/Core/Database/EntityQuery/ConditionInterface.php b/core/lib/Drupal/Core/Database/EntityQuery/ConditionInterface.php
deleted file mode 100644
index 18dfd49..0000000
--- a/core/lib/Drupal/Core/Database/EntityQuery/ConditionInterface.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\Core\Database\EntityQuery\ConditionInterface.
- */
-
-namespace Drupal\Core\Database\EntityQuery;
-
-/**
- * Provides an interface for entity query conditions for SQL databases.
- */
-interface ConditionInterface {
-
-  /**
-   * Translates the string operators to SQL equivalents. This is a no-op method
-   * for MySQL and SQLite databases but allows override if needed, e.g. for
-   * PostgreSQL to support case insensitive queries.
-   *
-   * @param array $condition
-   *   The condition array.
-   * @param bool|null $case_sensitive
-   *   If the condition should be case sensitive or not, NULL if the field does
-   *   not define it.
-   *
-   * @see \Drupal\Core\Entity\Query\Sql\Condition::$entityQueryCondition
-   */
-  public static function translateCondition(array &$condition, $case_sensitive);
-
-}
diff --git a/core/lib/Drupal/Core/Database/Query/Select.php b/core/lib/Drupal/Core/Database/Query/Select.php
index d925a07..8ccf16a 100644
--- a/core/lib/Drupal/Core/Database/Query/Select.php
+++ b/core/lib/Drupal/Core/Database/Query/Select.php
@@ -466,6 +466,13 @@ public function escapeLike($string) {
   /**
    * {@inheritdoc}
    */
+  public function escapeField($string) {
+    return $this->connection->escapeField($string);
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function getArguments(PlaceholderInterface $queryPlaceholder = NULL) {
     if (!isset($queryPlaceholder)) {
       $queryPlaceholder = $this;
diff --git a/core/lib/Drupal/Core/Database/Query/SelectExtender.php b/core/lib/Drupal/Core/Database/Query/SelectExtender.php
index f85aac4..cca68c7 100644
--- a/core/lib/Drupal/Core/Database/Query/SelectExtender.php
+++ b/core/lib/Drupal/Core/Database/Query/SelectExtender.php
@@ -210,6 +210,14 @@ public function escapeLike($string) {
     return $this->query->escapeLike($string);
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function escapeField($string) {
+    $this->query->escapeField($string);
+    return $this;
+  }
+
   public function getArguments(PlaceholderInterface $queryPlaceholder = NULL) {
     return $this->query->getArguments($queryPlaceholder);
   }
diff --git a/core/lib/Drupal/Core/Database/Query/SelectInterface.php b/core/lib/Drupal/Core/Database/Query/SelectInterface.php
index bfb7db6..6b87014 100644
--- a/core/lib/Drupal/Core/Database/Query/SelectInterface.php
+++ b/core/lib/Drupal/Core/Database/Query/SelectInterface.php
@@ -141,6 +141,18 @@ public function &getUnion();
   public function escapeLike($string);
 
   /**
+   * Escapes a field name string.
+   *
+   * Force all field names to be strictly alphanumeric-plus-underscore.
+   * For some database drivers, it may also wrap the field name in
+   * database-specific escape characters.
+   *
+   * @return
+   *   The sanitized field name string.
+   */
+  public function escapeField($string);
+
+  /**
    * Compiles and returns an associative array of the arguments for this prepared statement.
    *
    * @param $queryPlaceholder
@@ -632,4 +644,5 @@ public function __clone();
    *   The called object.
    */
   public function forUpdate($set = TRUE);
+
 }
diff --git a/core/lib/Drupal/Core/Entity/Query/ConditionFundamentals.php b/core/lib/Drupal/Core/Entity/Query/ConditionFundamentals.php
index 195479d..b93e192 100644
--- a/core/lib/Drupal/Core/Entity/Query/ConditionFundamentals.php
+++ b/core/lib/Drupal/Core/Entity/Query/ConditionFundamentals.php
@@ -37,14 +37,26 @@
   protected $query;
 
   /**
+   * List of potential namespaces of the classes belonging to this condition.
+   *
+   * @var array
+   */
+  protected $namespaces = array();
+
+  /**
    * Constructs a Condition object.
    *
    * @param string $conjunction
    *   The operator to use to combine conditions: 'AND' or 'OR'.
+   * @param QueryInterface $query
+   *   The entity query this condition belongs to.
+   * @param array $namespaces
+   *   List of potential namespaces of the classes belonging to this condition.
    */
-  public function __construct($conjunction, QueryInterface $query) {
+  public function __construct($conjunction, QueryInterface $query, $namespaces = []) {
     $this->conjunction = $conjunction;
     $this->query = $query;
+    $this->namespaces = $namespaces;
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/Condition.php b/core/lib/Drupal/Core/Entity/Query/Sql/Condition.php
index 3e71e56..1ee2c3d 100644
--- a/core/lib/Drupal/Core/Entity/Query/Sql/Condition.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/Condition.php
@@ -7,7 +7,6 @@
 
 namespace Drupal\Core\Entity\Query\Sql;
 
-use Drupal\Core\Database\Database;
 use Drupal\Core\Database\Query\SelectInterface;
 use Drupal\Core\Database\Query\Condition as SqlCondition;
 use Drupal\Core\Entity\Query\ConditionBase;
@@ -90,13 +89,8 @@ public function notExists($field, $langcode = NULL) {
    * @see \Drupal\Core\Database\Query\ConditionInterface::condition()
    */
   public static function translateCondition(&$condition, SelectInterface $sql_query, $case_sensitive) {
-    // There is nothing to do for IN () queries except for PostgreSQL for which
-    // the condition arguments need to have case lowered to support not case
-    // sensitive fields.
+    // // There is nothing we can do for IN ().
     if (is_array($condition['value'])) {
-      $entityQueryCondition = Database::getConnection()->getDriverClass('EntityQuery\\Condition');
-      $entityQueryCondition::translateCondition($condition, $case_sensitive);
-
       return;
     }
 
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/ConditionAggregate.php b/core/lib/Drupal/Core/Entity/Query/Sql/ConditionAggregate.php
index 584a883..9db67ea 100644
--- a/core/lib/Drupal/Core/Entity/Query/Sql/ConditionAggregate.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/ConditionAggregate.php
@@ -11,6 +11,7 @@
 use Drupal\Core\Entity\Query\ConditionAggregateBase;
 use Drupal\Core\Entity\Query\ConditionAggregateInterface;
 use Drupal\Core\Database\Query\Condition as SqlCondition;
+use Drupal\Core\Entity\Query\QueryBase;
 
 /**
  * Defines the aggregate condition for sql based storage.
@@ -39,7 +40,8 @@ public function compile($conditionContainer) {
       else {
         $type = ((strtoupper($this->conjunction) == 'OR') || ($condition['operator'] == 'IS NULL')) ? 'LEFT' : 'INNER';
         $field = $tables->addField($condition['field'], $type, $condition['langcode']);
-        Condition::translateCondition($condition, $sql_query, $tables->isFieldCaseSensitive($condition['field']));
+        $condition_class = QueryBase::getClass($this->namespaces, 'Condition');
+        $condition_class::translateCondition($condition, $sql_query, $tables->isFieldCaseSensitive($condition['field']));
         $function = $condition['function'];
         $placeholder = ':db_placeholder_' . $conditionContainer->nextPlaceholder();
         $conditionContainer->having("$function($field) {$condition['operator']} $placeholder", array($placeholder => $condition['value']));
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/QueryAggregate.php b/core/lib/Drupal/Core/Entity/Query/Sql/QueryAggregate.php
index c76a773..1d5a16e 100644
--- a/core/lib/Drupal/Core/Entity/Query/Sql/QueryAggregate.php
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/QueryAggregate.php
@@ -52,7 +52,8 @@ public function prepare() {
    * Implements \Drupal\Core\Entity\Query\QueryAggregateInterface::conditionAggregateGroupFactory().
    */
   public function conditionAggregateGroupFactory($conjunction = 'AND') {
-    return new ConditionAggregate($conjunction, $this);
+    $class = static::getClass($this->namespaces, 'ConditionAggregate');
+    return new $class($conjunction, $this, $this->namespaces);
   }
 
   /**
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/Condition.php b/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/Condition.php
new file mode 100644
index 0000000..5d61eab
--- /dev/null
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/Condition.php
@@ -0,0 +1,35 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Entity\Query\Sql\pgsql\Condition.
+ */
+
+namespace Drupal\Core\Entity\Query\Sql\pgsql;
+
+use Drupal\Core\Database\Query\SelectInterface;
+use Drupal\Core\Entity\Query\Sql\Condition as BaseCondition;
+
+class Condition extends BaseCondition {
+
+  public static function translateCondition(&$condition, SelectInterface $sql_query, $case_sensitive) {
+    if (is_array($condition['value']) && $case_sensitive === FALSE) {
+      $condition['where'] = 'LOWER(' . $sql_query->escapeField($condition['real_field']) . ') ' . $condition['operator'] . ' (';
+      $condition['where_args'] = [];
+
+      $n = 1;
+      // Only use the array values in case an associative array is passed as an
+      // argument following similar pattern in
+      // \Drupal\Core\Database\Connection::expandArguments().
+      foreach ($condition['value'] as $value) {
+        $condition['where'] .= 'LOWER(:value' . $n . '),';
+        $condition['where_args'][':value' . $n] = $value;
+        $n++;
+      }
+      $condition['where'] = trim($condition['where'], ',');
+      $condition['where'] .= ')';
+      return;
+    }
+    parent::translateCondition($condition, $sql_query, $case_sensitive);
+  }
+}
diff --git a/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/QueryFactory.php b/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/QueryFactory.php
new file mode 100644
index 0000000..fb43f13
--- /dev/null
+++ b/core/lib/Drupal/Core/Entity/Query/Sql/pgsql/QueryFactory.php
@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Core\Entity\Query\Sql\pgsql\QueryFactory.
+ */
+
+
+namespace Drupal\Core\Entity\Query\Sql\pgsql;
+
+use Drupal\Core\Entity\Query\Sql\QueryFactory as BaseQueryFactory;
+
+/**
+ * PostgreSQL specific entity query implementation.
+ *
+ * To add a new query implementation extending the default SQL one, add
+ * a service definition like pgsql.entity.query.sql and a factory class like
+ * this. The system will automatically find the relevant Query, QueryAggregate,
+ * Condition, ConditionAggregate, Tables classes in this namespace, in the
+ * namespace of the parent class and so on. So after creating an empty query
+ * factory class like this, it is possible to just drop in a class extending
+ * the base class in this namespace and it will be used automatically but it
+ * is optional: if a class is not extended the relevant default is used.
+ *
+ * @see \Drupal\Core\Entity\Query\QueryBase::getNamespaces()
+ * @see \Drupal\Core\Entity\Query\QueryBase::getClass()
+ */
+class QueryFactory extends BaseQueryFactory {
+
+}