Merge pull request #7880 from kuraobi/update-doc-dql-qb

Update documentation to recommend DQL over QueryBuilder when possible

Author: Ocramius

docs/en/reference/faq.rst

@@ -198,6 +198,21 @@ No, it is not supported to sort by function in DQL. If you need this functionali
 use a native-query or come up with another solution. As a side note: Sorting with ORDER BY RAND() is painfully slow
 starting with 1000 rows.
 
+Is it better to write DQL or to generate it with the query builder?
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The purpose of the ``QueryBuilder`` is to generate DQL dynamically,
+which is useful when you have optional filters, conditional joins, etc.
+
+But the ``QueryBuilder`` is not an alternative to DQL, it actually generates DQL
+queries at runtime, which are then interpreted by Doctrine. This means that
+using the ``QueryBuilder`` to build and run a query is actually always slower
+than only running the corresponding DQL query.
+
+So if you only need to generate a query and bind parameters to it,
+you should use plain DQL, as this is a simpler and much more readable solution.
+You should only use the ``QueryBuilder`` when you can't achieve what you want to do with a DQL query.
+
 A Query fails, how can I debug it?
 ----------------------------------
 

docs/en/reference/query-builder.rst

@@ -9,6 +9,12 @@ programmatically build queries, and also provides a fluent API.
 This means that you can change between one methodology to the other
 as you want, or just pick a preferred one.
 
+.. note::
+
+    The ``QueryBuilder`` is not an abstraction of DQL, but merely a tool to dynamically build it.
+    You should still use plain DQL when you can, as it is simpler and more readable.
+    More about this in the :doc:`FAQ <faq>`_.
+
 Constructing a new QueryBuilder object
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -80,7 +86,7 @@ Working with QueryBuilder
 High level API methods
 ^^^^^^^^^^^^^^^^^^^^^^
 
-To simplify even more the way you build a query in Doctrine, you can take
+The most straightforward way to build a dynamic query with the ``QueryBuilder`` is by taking
 advantage of Helper methods. For all base code, there is a set of
 useful methods to simplify a programmer's life. To illustrate how
 to work with them, here is the same example 6 re-written using
@@ -97,10 +103,9 @@ to work with them, here is the same example 6 re-written using
        ->orderBy('u.name', 'ASC');
 
 ``QueryBuilder`` helper methods are considered the standard way to
-build DQL queries. Although it is supported, using string-based
-queries should be avoided.  You are greatly encouraged to use
-``$qb->expr()->*`` methods. Here is a converted example 8 to
-suggested standard way to build queries:
+use the ``QueryBuilder``. The ``$qb->expr()->*`` methods can help you
+build conditional expressions dynamically. Here is a converted example 8 to
+suggested way to build queries with dynamic conditions:
 
 .. code-block:: php
 

docs/en/reference/working-with-objects.rst

@@ -800,7 +800,9 @@ DQL and its syntax as well as the Doctrine class can be found in
 :doc:`the dedicated chapter <dql-doctrine-query-language>`.
 For programmatically building up queries based on conditions that
 are only known at runtime, Doctrine provides the special
-``Doctrine\ORM\QueryBuilder`` class. More information on
+``Doctrine\ORM\QueryBuilder`` class. While this a powerful tool,
+it also brings more complexity to your code compared to plain DQL,
+so you should only use it when you need it. More information on
 constructing queries with a QueryBuilder can be found
 :doc:`in Query Builder chapter <query-builder>`.
 

docs/en/tutorials/getting-started.rst

@@ -1210,8 +1210,7 @@ The console output of this script is then:
     throw your ORM into the dumpster, because it doesn't support some
     the more powerful SQL concepts.
 
-
-    Instead of handwriting DQL you can use the ``QueryBuilder`` retrieved
+    If you need to build your query dynamically, you can use the ``QueryBuilder`` retrieved
     by calling ``$entityManager->createQueryBuilder()``. There are more
     details about this in the relevant part of the documentation.