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<h1><a href="../../index.html">Django 1.5.9 documentation</a></h1>
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<div class="yui-g" id="topics-db-transactions">
<div class="section" id="s-module-django.db.transaction">
<span id="s-managing-database-transactions"></span><span id="module-django.db.transaction"></span><span id="managing-database-transactions"></span><h1>Managing database transactions<a class="headerlink" href="#module-django.db.transaction" title="Permalink to this headline">¶</a></h1>
<p>Django gives you a few ways to control how database transactions are managed,
if you’re using a database that supports transactions.</p>
<div class="section" id="s-django-s-default-transaction-behavior">
<span id="django-s-default-transaction-behavior"></span><h2>Django’s default transaction behavior<a class="headerlink" href="#django-s-default-transaction-behavior" title="Permalink to this headline">¶</a></h2>
<p>Django’s default behavior is to run with an open transaction which it
commits automatically when any built-in, data-altering model function is
called. For example, if you call <tt class="docutils literal"><span class="pre">model.save()</span></tt> or <tt class="docutils literal"><span class="pre">model.delete()</span></tt>, the
change will be committed immediately.</p>
<p>This is much like the auto-commit setting for most databases. As soon as you
perform an action that needs to write to the database, Django produces the
<tt class="docutils literal"><span class="pre">INSERT</span></tt>/<tt class="docutils literal"><span class="pre">UPDATE</span></tt>/<tt class="docutils literal"><span class="pre">DELETE</span></tt> statements and then does the <tt class="docutils literal"><span class="pre">COMMIT</span></tt>.
There’s no implicit <tt class="docutils literal"><span class="pre">ROLLBACK</span></tt>.</p>
</div>
<div class="section" id="s-tying-transactions-to-http-requests">
<span id="tying-transactions-to-http-requests"></span><h2>Tying transactions to HTTP requests<a class="headerlink" href="#tying-transactions-to-http-requests" title="Permalink to this headline">¶</a></h2>
<p>The recommended way to handle transactions in Web requests is to tie them to
the request and response phases via Django’s <tt class="docutils literal"><span class="pre">TransactionMiddleware</span></tt>.</p>
<p>It works like this: When a request starts, Django starts a transaction. If the
response is produced without problems, Django commits any pending transactions.
If the view function produces an exception, Django rolls back any pending
transactions.</p>
<p>To activate this feature, just add the <tt class="docutils literal"><span class="pre">TransactionMiddleware</span></tt> middleware to
your <a class="reference internal" href="../../ref/settings.html#std:setting-MIDDLEWARE_CLASSES"><tt class="xref std std-setting docutils literal"><span class="pre">MIDDLEWARE_CLASSES</span></tt></a> setting:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">MIDDLEWARE_CLASSES</span> <span class="o">=</span> <span class="p">(</span>
<span class="s">'django.middleware.cache.UpdateCacheMiddleware'</span><span class="p">,</span>
<span class="s">'django.contrib.sessions.middleware.SessionMiddleware'</span><span class="p">,</span>
<span class="s">'django.middleware.common.CommonMiddleware'</span><span class="p">,</span>
<span class="s">'django.middleware.transaction.TransactionMiddleware'</span><span class="p">,</span>
<span class="s">'django.middleware.cache.FetchFromCacheMiddleware'</span><span class="p">,</span>
<span class="p">)</span>
</pre></div>
</div>
<p>The order is quite important. The transaction middleware applies not only to
view functions, but also for all middleware modules that come after it. So if
you use the session middleware after the transaction middleware, session
creation will be part of the transaction.</p>
<p>The various cache middlewares are an exception:
<tt class="docutils literal"><span class="pre">CacheMiddleware</span></tt>, <a class="reference internal" href="../../ref/middleware.html#django.middleware.cache.UpdateCacheMiddleware" title="django.middleware.cache.UpdateCacheMiddleware"><tt class="xref py py-class docutils literal"><span class="pre">UpdateCacheMiddleware</span></tt></a>,
and <a class="reference internal" href="../../ref/middleware.html#django.middleware.cache.FetchFromCacheMiddleware" title="django.middleware.cache.FetchFromCacheMiddleware"><tt class="xref py py-class docutils literal"><span class="pre">FetchFromCacheMiddleware</span></tt></a> are never
affected. Even when using database caching, Django’s cache backend uses its own
database cursor (which is mapped to its own database connection internally).</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">The <tt class="docutils literal"><span class="pre">TransactionMiddleware</span></tt> only affects the database aliased
as “default” within your <a class="reference internal" href="../../ref/settings.html#std:setting-DATABASES"><tt class="xref std std-setting docutils literal"><span class="pre">DATABASES</span></tt></a> setting. If you are using
multiple databases and want transaction control over databases other than
“default”, you will need to write your own transaction middleware.</p>
</div>
</div>
<div class="section" id="s-controlling-transaction-management-in-views">
<span id="s-transaction-management-functions"></span><span id="controlling-transaction-management-in-views"></span><span id="transaction-management-functions"></span><h2>Controlling transaction management in views<a class="headerlink" href="#controlling-transaction-management-in-views" title="Permalink to this headline">¶</a></h2>
<p>For most people, implicit request-based transactions work wonderfully. However,
if you need more fine-grained control over how transactions are managed, you can
use a set of functions in <tt class="docutils literal"><span class="pre">django.db.transaction</span></tt> to control transactions on a
per-function or per-code-block basis.</p>
<p>These functions, described in detail below, can be used in two different ways:</p>
<ul>
<li><p class="first">As a <a class="reference external" href="http://docs.python.org/glossary.html#term-decorator">decorator</a> on a particular function. For example:</p>
<div class="highlight-python"><pre>from django.db import transaction
@transaction.commit_on_success
def viewfunc(request):
# ...
# this code executes inside a transaction
# ...</pre>
</div>
</li>
<li><p class="first">As a <a class="reference external" href="http://docs.python.org/glossary.html#term-context-manager">context manager</a> around a particular block of code:</p>
<div class="highlight-python"><pre>from django.db import transaction
def viewfunc(request):
# ...
# this code executes using default transaction management
# ...
with transaction.commit_on_success():
# ...
# this code executes inside a transaction
# ...</pre>
</div>
</li>
</ul>
<p>Both techniques work with all supported version of Python.</p>
<p>For maximum compatibility, all of the examples below show transactions using the
decorator syntax, but all of the follow functions may be used as context
managers, too.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">Although the examples below use view functions as examples, these
decorators and context managers can be used anywhere in your code
that you need to deal with transactions.</p>
</div>
<span class="target" id="topics-db-transactions-autocommit"></span><dl class="function">
<dt id="django.db.transaction.autocommit">
<tt class="descname">autocommit</tt>()<a class="headerlink" href="#django.db.transaction.autocommit" title="Permalink to this definition">¶</a></dt>
<dd><p>Use the <tt class="docutils literal"><span class="pre">autocommit</span></tt> decorator to switch a view function to Django’s
default commit behavior, regardless of the global transaction setting.</p>
<p>Example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">django.db</span> <span class="kn">import</span> <span class="n">transaction</span>
<span class="nd">@transaction.autocommit</span>
<span class="k">def</span> <span class="nf">viewfunc</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">....</span>
<span class="nd">@transaction.autocommit</span><span class="p">(</span><span class="n">using</span><span class="o">=</span><span class="s">"my_other_database"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">viewfunc2</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">....</span>
</pre></div>
</div>
<p>Within <tt class="docutils literal"><span class="pre">viewfunc()</span></tt>, transactions will be committed as soon as you call
<tt class="docutils literal"><span class="pre">model.save()</span></tt>, <tt class="docutils literal"><span class="pre">model.delete()</span></tt>, or any other function that writes to
the database. <tt class="docutils literal"><span class="pre">viewfunc2()</span></tt> will have this same behavior, but for the
<tt class="docutils literal"><span class="pre">"my_other_database"</span></tt> connection.</p>
</dd></dl>
<dl class="function">
<dt id="django.db.transaction.commit_on_success">
<tt class="descname">commit_on_success</tt>()<a class="headerlink" href="#django.db.transaction.commit_on_success" title="Permalink to this definition">¶</a></dt>
<dd><p>Use the <tt class="docutils literal"><span class="pre">commit_on_success</span></tt> decorator to use a single transaction for all
the work done in a function:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">django.db</span> <span class="kn">import</span> <span class="n">transaction</span>
<span class="nd">@transaction.commit_on_success</span>
<span class="k">def</span> <span class="nf">viewfunc</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">....</span>
<span class="nd">@transaction.commit_on_success</span><span class="p">(</span><span class="n">using</span><span class="o">=</span><span class="s">"my_other_database"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">viewfunc2</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">....</span>
</pre></div>
</div>
<p>If the function returns successfully, then Django will commit all work done
within the function at that point. If the function raises an exception,
though, Django will roll back the transaction.</p>
</dd></dl>
<dl class="function">
<dt id="django.db.transaction.commit_manually">
<tt class="descname">commit_manually</tt>()<a class="headerlink" href="#django.db.transaction.commit_manually" title="Permalink to this definition">¶</a></dt>
<dd><p>Use the <tt class="docutils literal"><span class="pre">commit_manually</span></tt> decorator if you need full control over
transactions. It tells Django you’ll be managing the transaction on your
own.</p>
<p>Whether you are writing or simply reading from the database, you must
<tt class="docutils literal"><span class="pre">commit()</span></tt> or <tt class="docutils literal"><span class="pre">rollback()</span></tt> explicitly or Django will raise a
<a class="reference internal" href="../../ref/exceptions.html#django.db.transaction.TransactionManagementError" title="django.db.transaction.TransactionManagementError"><tt class="xref py py-exc docutils literal"><span class="pre">TransactionManagementError</span></tt></a> exception. This is required when reading
from the database because <tt class="docutils literal"><span class="pre">SELECT</span></tt> statements may call functions which
modify tables, and thus it is impossible to know if any data has been
modified.</p>
<p>Manual transaction management looks like this:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">django.db</span> <span class="kn">import</span> <span class="n">transaction</span>
<span class="nd">@transaction.commit_manually</span>
<span class="k">def</span> <span class="nf">viewfunc</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">...</span>
<span class="c"># You can commit/rollback however and whenever you want</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="o">...</span>
<span class="c"># But you've got to remember to do it yourself!</span>
<span class="k">try</span><span class="p">:</span>
<span class="o">...</span>
<span class="k">except</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">rollback</span><span class="p">()</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
<span class="nd">@transaction.commit_manually</span><span class="p">(</span><span class="n">using</span><span class="o">=</span><span class="s">"my_other_database"</span><span class="p">)</span>
<span class="k">def</span> <span class="nf">viewfunc2</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="o">....</span>
</pre></div>
</div>
</dd></dl>
</div>
<div class="section" id="s-requirements-for-transaction-handling">
<span id="s-topics-db-transactions-requirements"></span><span id="requirements-for-transaction-handling"></span><span id="topics-db-transactions-requirements"></span><h2>Requirements for transaction handling<a class="headerlink" href="#requirements-for-transaction-handling" title="Permalink to this headline">¶</a></h2>
<p>Django requires that every transaction that is opened is closed before
the completion of a request. If you are using <a class="reference internal" href="#django.db.transaction.autocommit" title="django.db.transaction.autocommit"><tt class="xref py py-func docutils literal"><span class="pre">autocommit()</span></tt></a> (the
default commit mode) or <a class="reference internal" href="#django.db.transaction.commit_on_success" title="django.db.transaction.commit_on_success"><tt class="xref py py-func docutils literal"><span class="pre">commit_on_success()</span></tt></a>, this will be done
for you automatically (with the exception of <a class="reference internal" href="sql.html#executing-custom-sql"><em>executing custom SQL</em></a>). However, if you are manually managing
transactions (using the <a class="reference internal" href="#django.db.transaction.commit_manually" title="django.db.transaction.commit_manually"><tt class="xref py py-func docutils literal"><span class="pre">commit_manually()</span></tt></a> decorator), you must
ensure that the transaction is either committed or rolled back before
a request is completed.</p>
<p>This applies to all database operations, not just write operations. Even
if your transaction only reads from the database, the transaction must
be committed or rolled back before you complete a request.</p>
</div>
<div class="section" id="s-how-to-globally-deactivate-transaction-management">
<span id="s-deactivate-transaction-management"></span><span id="how-to-globally-deactivate-transaction-management"></span><span id="deactivate-transaction-management"></span><h2>How to globally deactivate transaction management<a class="headerlink" href="#how-to-globally-deactivate-transaction-management" title="Permalink to this headline">¶</a></h2>
<p>Control freaks can totally disable all transaction management by setting
<a class="reference internal" href="../../ref/settings.html#std:setting-TRANSACTIONS_MANAGED"><tt class="xref std std-setting docutils literal"><span class="pre">TRANSACTIONS_MANAGED</span></tt></a> to <tt class="docutils literal"><span class="pre">True</span></tt> in the Django settings file.</p>
<p>If you do this, Django won’t provide any automatic transaction management
whatsoever. Middleware will no longer implicitly commit transactions, and
you’ll need to roll management yourself. This even requires you to commit
changes done by middleware somewhere else.</p>
<p>Thus, this is best used in situations where you want to run your own
transaction-controlling middleware or do something really strange. In almost
all situations, you’ll be better off using the default behavior, or the
transaction middleware, and only modify selected functions as needed.</p>
</div>
<div class="section" id="s-savepoints">
<span id="s-topics-db-transactions-savepoints"></span><span id="savepoints"></span><span id="topics-db-transactions-savepoints"></span><h2>Savepoints<a class="headerlink" href="#savepoints" title="Permalink to this headline">¶</a></h2>
<p>A savepoint is a marker within a transaction that enables you to roll back part
of a transaction, rather than the full transaction. Savepoints are available
with the PostgreSQL 8, Oracle and MySQL (when using the InnoDB storage engine)
backends. Other backends provide the savepoint functions, but they’re empty
operations – they don’t actually do anything.</p>
<div class="versionchanged">
<span class="title">Changed in Django 1.4:</span> Savepoint support for the MySQL backend was added in Django 1.4.</div>
<p>Savepoints aren’t especially useful if you are using the default
<tt class="docutils literal"><span class="pre">autocommit</span></tt> behavior of Django. However, if you are using
<tt class="docutils literal"><span class="pre">commit_on_success</span></tt> or <tt class="docutils literal"><span class="pre">commit_manually</span></tt>, each open transaction will build
up a series of database operations, awaiting a commit or rollback. If you
issue a rollback, the entire transaction is rolled back. Savepoints provide
the ability to perform a fine-grained rollback, rather than the full rollback
that would be performed by <tt class="docutils literal"><span class="pre">transaction.rollback()</span></tt>.</p>
<p>Each of these functions takes a <tt class="docutils literal"><span class="pre">using</span></tt> argument which should be the name of
a database for which the behavior applies. If no <tt class="docutils literal"><span class="pre">using</span></tt> argument is
provided then the <tt class="docutils literal"><span class="pre">"default"</span></tt> database is used.</p>
<p>Savepoints are controlled by three methods on the transaction object:</p>
<dl class="method">
<dt id="django.db.transaction.transaction.savepoint">
<tt class="descclassname">transaction.</tt><tt class="descname">savepoint</tt>(<em>using=None</em>)<a class="headerlink" href="#django.db.transaction.transaction.savepoint" title="Permalink to this definition">¶</a></dt>
<dd><p>Creates a new savepoint. This marks a point in the transaction that
is known to be in a “good” state.</p>
<p>Returns the savepoint ID (sid).</p>
</dd></dl>
<dl class="method">
<dt id="django.db.transaction.transaction.savepoint_commit">
<tt class="descclassname">transaction.</tt><tt class="descname">savepoint_commit</tt>(<em>sid</em>, <em>using=None</em>)<a class="headerlink" href="#django.db.transaction.transaction.savepoint_commit" title="Permalink to this definition">¶</a></dt>
<dd><p>Updates the savepoint to include any operations that have been performed
since the savepoint was created, or since the last commit.</p>
</dd></dl>
<dl class="method">
<dt id="django.db.transaction.transaction.savepoint_rollback">
<tt class="descclassname">transaction.</tt><tt class="descname">savepoint_rollback</tt>(<em>sid</em>, <em>using=None</em>)<a class="headerlink" href="#django.db.transaction.transaction.savepoint_rollback" title="Permalink to this definition">¶</a></dt>
<dd><p>Rolls the transaction back to the last point at which the savepoint was
committed.</p>
</dd></dl>
<p>The following example demonstrates the use of savepoints:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">django.db</span> <span class="kn">import</span> <span class="n">transaction</span>
<span class="nd">@transaction.commit_manually</span>
<span class="k">def</span> <span class="nf">viewfunc</span><span class="p">(</span><span class="n">request</span><span class="p">):</span>
<span class="n">a</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
<span class="c"># open transaction now contains a.save()</span>
<span class="n">sid</span> <span class="o">=</span> <span class="n">transaction</span><span class="o">.</span><span class="n">savepoint</span><span class="p">()</span>
<span class="n">b</span><span class="o">.</span><span class="n">save</span><span class="p">()</span>
<span class="c"># open transaction now contains a.save() and b.save()</span>
<span class="k">if</span> <span class="n">want_to_keep_b</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">savepoint_commit</span><span class="p">(</span><span class="n">sid</span><span class="p">)</span>
<span class="c"># open transaction still contains a.save() and b.save()</span>
<span class="k">else</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">savepoint_rollback</span><span class="p">(</span><span class="n">sid</span><span class="p">)</span>
<span class="c"># open transaction now contains only a.save()</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">commit</span><span class="p">()</span>
</pre></div>
</div>
</div>
<div class="section" id="s-transactions-in-mysql">
<span id="transactions-in-mysql"></span><h2>Transactions in MySQL<a class="headerlink" href="#transactions-in-mysql" title="Permalink to this headline">¶</a></h2>
<p>If you’re using MySQL, your tables may or may not support transactions; it
depends on your MySQL version and the table types you’re using. (By
“table types,” we mean something like “InnoDB” or “MyISAM”.) MySQL transaction
peculiarities are outside the scope of this article, but the MySQL site has
<a class="reference external" href="http://dev.mysql.com/doc/refman/5.0/en/sql-syntax-transactions.html">information on MySQL transactions</a>.</p>
<p>If your MySQL setup does <em>not</em> support transactions, then Django will function
in auto-commit mode: Statements will be executed and committed as soon as
they’re called. If your MySQL setup <em>does</em> support transactions, Django will
handle transactions as explained in this document.</p>
</div>
<div class="section" id="s-handling-exceptions-within-postgresql-transactions">
<span id="handling-exceptions-within-postgresql-transactions"></span><h2>Handling exceptions within PostgreSQL transactions<a class="headerlink" href="#handling-exceptions-within-postgresql-transactions" title="Permalink to this headline">¶</a></h2>
<p>When a call to a PostgreSQL cursor raises an exception (typically
<tt class="docutils literal"><span class="pre">IntegrityError</span></tt>), all subsequent SQL in the same transaction will fail with
the error “current transaction is aborted, queries ignored until end of
transaction block”. Whilst simple use of <tt class="docutils literal"><span class="pre">save()</span></tt> is unlikely to raise an
exception in PostgreSQL, there are more advanced usage patterns which
might, such as saving objects with unique fields, saving using the
force_insert/force_update flag, or invoking custom SQL.</p>
<p>There are several ways to recover from this sort of error.</p>
<div class="section" id="s-transaction-rollback">
<span id="transaction-rollback"></span><h3>Transaction rollback<a class="headerlink" href="#transaction-rollback" title="Permalink to this headline">¶</a></h3>
<p>The first option is to roll back the entire transaction. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">a</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Succeeds, but may be undone by transaction rollback</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">b</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Could throw exception</span>
<span class="k">except</span> <span class="n">IntegrityError</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">rollback</span><span class="p">()</span>
<span class="n">c</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Succeeds, but a.save() may have been undone</span>
</pre></div>
</div>
<p>Calling <tt class="docutils literal"><span class="pre">transaction.rollback()</span></tt> rolls back the entire transaction. Any
uncommitted database operations will be lost. In this example, the changes
made by <tt class="docutils literal"><span class="pre">a.save()</span></tt> would be lost, even though that operation raised no error
itself.</p>
</div>
<div class="section" id="s-savepoint-rollback">
<span id="savepoint-rollback"></span><h3>Savepoint rollback<a class="headerlink" href="#savepoint-rollback" title="Permalink to this headline">¶</a></h3>
<p>If you are using PostgreSQL 8 or later, you can use <a class="reference internal" href="#topics-db-transactions-savepoints"><em>savepoints</em></a> to control the extent of a rollback.
Before performing a database operation that could fail, you can set or update
the savepoint; that way, if the operation fails, you can roll back the single
offending operation, rather than the entire transaction. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">a</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Succeeds, and never undone by savepoint rollback</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">sid</span> <span class="o">=</span> <span class="n">transaction</span><span class="o">.</span><span class="n">savepoint</span><span class="p">()</span>
<span class="n">b</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Could throw exception</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">savepoint_commit</span><span class="p">(</span><span class="n">sid</span><span class="p">)</span>
<span class="k">except</span> <span class="n">IntegrityError</span><span class="p">:</span>
<span class="n">transaction</span><span class="o">.</span><span class="n">savepoint_rollback</span><span class="p">(</span><span class="n">sid</span><span class="p">)</span>
<span class="n">c</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Succeeds, and a.save() is never undone</span>
</pre></div>
</div>
<p>In this example, <tt class="docutils literal"><span class="pre">a.save()</span></tt> will not be undone in the case where
<tt class="docutils literal"><span class="pre">b.save()</span></tt> raises an exception.</p>
</div>
<div class="section" id="s-database-level-autocommit">
<span id="database-level-autocommit"></span><h3>Database-level autocommit<a class="headerlink" href="#database-level-autocommit" title="Permalink to this headline">¶</a></h3>
<p>With PostgreSQL 8.2 or later, there is an advanced option to run PostgreSQL
with <a class="reference internal" href="../../ref/databases.html"><em>database-level autocommit</em></a>. If you use this option,
there is no constantly open transaction, so it is always possible to continue
after catching an exception. For example:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">a</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># succeeds</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">b</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># Could throw exception</span>
<span class="k">except</span> <span class="n">IntegrityError</span><span class="p">:</span>
<span class="k">pass</span>
<span class="n">c</span><span class="o">.</span><span class="n">save</span><span class="p">()</span> <span class="c"># succeeds</span>
</pre></div>
</div>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">This is not the same as the <a class="reference internal" href="#topics-db-transactions-autocommit"><em>autocommit decorator</em></a>. When using database level autocommit
there is no database transaction at all. The <tt class="docutils literal"><span class="pre">autocommit</span></tt> decorator
still uses transactions, automatically committing each transaction when
a database modifying operation occurs.</p>
</div>
</div>
</div>
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<h3><a href="../../contents.html">Table Of Contents</a></h3>
<ul>
<li><a class="reference internal" href="#">Managing database transactions</a><ul>
<li><a class="reference internal" href="#django-s-default-transaction-behavior">Django’s default transaction behavior</a></li>
<li><a class="reference internal" href="#tying-transactions-to-http-requests">Tying transactions to HTTP requests</a></li>
<li><a class="reference internal" href="#controlling-transaction-management-in-views">Controlling transaction management in views</a></li>
<li><a class="reference internal" href="#requirements-for-transaction-handling">Requirements for transaction handling</a></li>
<li><a class="reference internal" href="#how-to-globally-deactivate-transaction-management">How to globally deactivate transaction management</a></li>
<li><a class="reference internal" href="#savepoints">Savepoints</a></li>
<li><a class="reference internal" href="#transactions-in-mysql">Transactions in MySQL</a></li>
<li><a class="reference internal" href="#handling-exceptions-within-postgresql-transactions">Handling exceptions within PostgreSQL transactions</a><ul>
<li><a class="reference internal" href="#transaction-rollback">Transaction rollback</a></li>
<li><a class="reference internal" href="#savepoint-rollback">Savepoint rollback</a></li>
<li><a class="reference internal" href="#database-level-autocommit">Database-level autocommit</a></li>
</ul>
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