feedback

Author: norareidy

source/includes/interact-data/transactions.py

@@ -34,18 +34,21 @@ def insert_movie_with_callback():
             runtime=140,
             genres=["Horror", "Comedy"]
         )
-        
         transaction.on_commit(get_horror_comedies)
 # end-callback
 
 # start-handle-errors
-movie = Movie.objects.get(
-    title="Jurassic Park",
-    released=timezone.make_aware(datetime(1993, 6, 11))
-)
+movie = Movie.objects.get(title="Jurassic Park")
+movie.title = "Jurassic Park I"
 try:
     with transaction.atomic():
-        movie.update(title="Jurassic Park I")
+        movie.save()
 except DatabaseError:
-    movie.update(title="Jurassic Park")
+    movie.title = "Jurassic Park"
+
+if movie.title == "Jurassic Park I":
+    movie.plot = "An industrialist invites experts to visit his theme park of cloned dinosaurs. After a power failure," \
+    "   the creatures run loose, putting everyone's lives, including his grandchildren's, in danger."
+    movie.save()
+
 # end-handle-errors

source/interact-data/transactions.txt

@@ -24,7 +24,7 @@ In this guide, you can learn how to use {+django-odm+} to perform
 **transactions**. Transactions allow you to run a series of operations
 that change data only if the entire transaction is committed.
 If any operation in the transaction does not succeed, {+django-odm+} stops the
-transaction and discards all data changes before they ever become
+transaction and discards all changes to the data before they ever become
 visible. This feature is called **atomicity**.
 
 In MongoDB, transactions run within logical sessions. A
@@ -80,10 +80,10 @@ To start a database transaction, define an atomic block of code
 by adding the ``@transaction.atomic`` decorator above your function.
 This decorator guarantees the atomicity of any database operations
 within the function. If the function successfully completes, the 
-changes are committed MongoDB.
+changes are committed to MongoDB.
 
 The following example calls the ``create()`` method within a transaction,
-inserting a document into the ``sample_mflix.movies`` collection if the
+which inserts a document into the ``sample_mflix.movies`` collection if the
 transaction succeeds:
 
 .. literalinclude:: /includes/interact-data/transactions.py
@@ -105,8 +105,8 @@ preceding example but uses a context manager to start a transaction:
 Run Callbacks After a Transaction
 ---------------------------------
 
-If you want to perform certain actions only if a transaction successfully
-completes, you can use the ``transaction.on_commit()`` method. This method allows you to
+To perform certain actions only if a transaction successfully completes,
+you can use the ``transaction.on_commit()`` function. This function allows you to
 register callbacks that run after a transaction is committed to the 
 database. Pass a function, or any callable object, as an argument to
 ``on_commit()``.
@@ -124,11 +124,12 @@ Handle Transaction Errors
 -------------------------
 
 To handle exceptions that occur during a transaction, add error handling
-logic around your atomic code block. If you include error handing logic inside
-the atomic block, {+framework+} might ignore these errors, resulting in unexpected
-behavior.
+logic around your atomic code block. If you handle errors inside
+the atomic block, you might obscure these errors from {+framework+}. Since
+{+framework+} uses errors to determine whether to commit or roll
+back a transaction, this can cause unexpected behavior.
 
-If a transaction does not succeed, your application does not revert any changes made
+If a transaction does not succeed, Django does not revert any changes made
 to a model's fields. To avoid inconsistencies between your models and database documents,
 you might need to manually restore the original field values.
 

source/limitations-upcoming.txt

@@ -257,8 +257,7 @@ Database and Collection Support
        - If a transaction generates an error, the transaction is no longer usable.
        - Savepoints, or nested atomic blocks, are not supported. The outermost atomic block starts
          a transaction, and any subsequent atomic blocks have no effect.
-       - Migration operations do not run inside a transaction, which differs from {+framework+}'s
-         default migration behavior.
+       - Migration operations do not run inside a transaction.
        - Your MongoDB deployment must be a replica set or sharded cluster.
      - *Partially Supported*.