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<div class="section" id="pysqlite-differences">
<span id="pysqlitediffs"></span><h1>pysqlite differences<a class="headerlink" href="#pysqlite-differences" title="Permalink to this headline">¶</a></h1>
<p>pysqlite and APSW approached the problem of providing access to SQLite
from Python from fundamentally different directions.</p>
<p>APSW only wraps version 3 of SQLite and provides access in whatever
way is normal for SQLite. It makes no effort to hide how SQLite is
different from other databases.</p>
<p>pysqlite tries to provide a DBAPI compliant wrapper for SQLite and in
doing so needs to make it have the same behaviour as other databases.
Consequently it does hide some of SQLite’s nuances.</p>
<div class="admonition note">
<p class="first admonition-title">Note</p>
<p class="last">I suggest using APSW when you want to directly use SQLite and its
functionality or are using your own code to deal with database
independence rather than DBAPI. Use pysqlite and DBAPI if your
needs are simple, and you don’t want to use SQLite features.</p>
</div>
<div class="section" id="what-apsw-does-better">
<h2>What APSW does better<a class="headerlink" href="#what-apsw-does-better" title="Permalink to this headline">¶</a></h2>
<p>APSW has the following enhancements/differences over pysqlite 2 (wrapping SQLite 3):</p>
<ul>
<li><p class="first">APSW stays up to date with SQLite. As features are added and
functionality changed in SQLite, APSW tracks them.</p>
</li>
<li><p class="first">APSW gives all functionality of SQLite including <a class="reference internal" href="vtable.html#virtualtables"><em>virtual
tables</em></a>, <a class="reference internal" href="vfs.html#vfs"><em>Virtual File System (VFS)</em></a>, <a class="reference internal" href="blob.html#blobio"><em>BLOB I/O</em></a>,
<a class="reference internal" href="backup.html#backup"><em>backups</em></a> and <a class="reference internal" href="connection.html#apsw.Connection.filecontrol" title="apsw.Connection.filecontrol"><tt class="xref py py-meth docutils literal"><span class="pre">file</span> <span class="pre">control</span></tt></a>.</p>
</li>
<li><p class="first">You can use the same <a class="reference internal" href="connection.html#apsw.Connection" title="apsw.Connection"><tt class="xref py py-class docutils literal"><span class="pre">Connection</span></tt></a> across threads with APSW
without needing any additional level of locking. pysqlite requires
that the <a class="reference internal" href="connection.html#apsw.Connection" title="apsw.Connection"><tt class="xref py py-class docutils literal"><span class="pre">Connection</span></tt></a> and any <a class="reference internal" href="cursor.html#apsw.Cursor" title="apsw.Cursor"><tt class="xref py py-class docutils literal"><span class="pre">cursors</span></tt></a> are
used in the same thread. You can disable its checking, but unless you
are very careful with your own mutexes you will have a crash or a
deadlock.</p>
</li>
<li><p class="first">APSW is a single file for the extension, <tt class="file docutils literal"><span class="pre">apsw.pyd</span></tt> on Windows
and <tt class="file docutils literal"><span class="pre">apsw.so</span></tt> on Unix/Mac (Note <span class="target" id="index-0"></span><a class="pep reference external" href="http://www.python.org/dev/peps/pep-3149"><strong>PEP 3149</strong></a>). There are no
other files needed and the <a class="reference internal" href="build.html#building"><em>build instructions</em></a> show
you how to include SQLite statically in this file. You can put this
file anywhere your Python session can reach. pysqlite is one binary
file and several .py files, all of which need to be available.</p>
</li>
<li><p class="first"><strong>Nothing</strong> happens behind your back. By default pysqlite tries to
manage transactions by parsing your SQL for you, but you can turn it
off. This can result in very unexpected behaviour with pysqlite.</p>
</li>
<li><p class="first">When using a <a class="reference internal" href="connection.html#apsw.Connection" title="apsw.Connection"><tt class="xref py py-class docutils literal"><span class="pre">Connection</span></tt></a> as a <a class="reference internal" href="connection.html#apsw.Connection.__enter__" title="apsw.Connection.__enter__"><tt class="xref py py-meth docutils literal"><span class="pre">context</span> <span class="pre">manager</span></tt></a> APSW uses SQLite’s ability to have <a class="reference external" href="https://sqlite.org/lang_savepoint.html">nested
transactions</a>.
pysqlite only deals with one transaction at a time and cannot nest
them. (Savepoints were introduced in SQLite 3.6.8 - another
illustration of the benefits of keeping up to date with SQLite.)</p>
</li>
<li><p class="first">APSW <strong>always</strong> handles Unicode correctly (this was one of the major
reasons for writing it in the first place). pysqlite has since fixed
many of its issues but you are still stuck with some.</p>
</li>
<li><p class="first">You can use semi-colons at the end of commands and you can have
multiple commands in the execute string in APSW. There are no
restrictions on the type of commands used. For example this will
work fine in APSW but is not allowed in pysqlite:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">import</span> <span class="nn">apsw</span>
<span class="n">con</span><span class="o">=</span><span class="n">apsw</span><span class="o">.</span><span class="n">Connection</span><span class="p">(</span><span class="s">":memory:"</span><span class="p">)</span>
<span class="n">cur</span><span class="o">=</span><span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s">"create table foo(x,y,z);insert into foo values (?,?,?);"</span>
<span class="s">"insert into foo values(?,?,?);select * from foo;drop table foo;"</span>
<span class="s">"create table bar(x,y);insert into bar values(?,?);"</span>
<span class="s">"insert into bar values(?,?);select * from bar;"</span><span class="p">,</span>
<span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="mi">6</span><span class="p">,</span><span class="mi">7</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">9</span><span class="p">,</span><span class="mi">10</span><span class="p">)):</span>
<span class="k">print</span> <span class="n">row</span>
</pre></div>
</div>
<p>And the output as you would expect:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">,</span> <span class="mi">3</span><span class="p">)</span>
<span class="p">(</span><span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span><span class="p">)</span>
<span class="p">(</span><span class="mi">7</span><span class="p">,</span> <span class="mi">8</span><span class="p">)</span>
<span class="p">(</span><span class="mi">9</span><span class="p">,</span> <span class="mi">10</span><span class="p">)</span>
</pre></div>
</div>
</li>
<li><p class="first"><a class="reference internal" href="cursor.html#apsw.Cursor.executemany" title="apsw.Cursor.executemany"><tt class="xref py py-meth docutils literal"><span class="pre">Cursor.executemany()</span></tt></a> also works with statements that return
data such as selects, and you can have multiple statements.
pysqlite’s <tt class="xref py py-meth docutils literal"><span class="pre">executescript()</span></tt> method doesn’t allow any form of
data being returned (it silently ignores any returned data).</p>
</li>
<li><p class="first">pysqlite swallows exceptions in your callbacks making it far harder
to debug problems. That also prevents you from raising exceptions in
your callbacks to be handled in your code that called
SQLite. pysqlite does let you turn on <a class="reference external" href="http://readthedocs.org/docs/pysqlite/en/latest/sqlite3.html#sqlite3.enable_callback_tracebacks">printing of tracebacks</a>,
but
that is a poor substitute. apsw does the right thing as demonstrated
by this example.</p>
<p>Source:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">def</span> <span class="nf">badfunc</span><span class="p">(</span><span class="n">t</span><span class="p">):</span>
<span class="k">return</span> <span class="mi">1</span><span class="o">/</span><span class="mi">0</span>
<span class="c"># pysqlite</span>
<span class="kn">from</span> <span class="nn">pysqlite2</span> <span class="kn">import</span> <span class="n">dbapi2</span> <span class="k">as</span> <span class="n">sqlite</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">sqlite</span><span class="o">.</span><span class="n">connect</span><span class="p">(</span><span class="s">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">create_function</span><span class="p">(</span><span class="s">"badfunc"</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">badfunc</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s">"select badfunc(3)"</span><span class="p">)</span>
<span class="c"># apsw</span>
<span class="kn">import</span> <span class="nn">apsw</span>
<span class="n">con</span> <span class="o">=</span> <span class="n">apsw</span><span class="o">.</span><span class="n">Connection</span><span class="p">(</span><span class="s">":memory:"</span><span class="p">)</span>
<span class="n">con</span><span class="o">.</span><span class="n">createscalarfunction</span><span class="p">(</span><span class="s">"badfunc"</span><span class="p">,</span> <span class="n">badfunc</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>
<span class="n">cur</span> <span class="o">=</span> <span class="n">con</span><span class="o">.</span><span class="n">cursor</span><span class="p">()</span>
<span class="n">cur</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s">"select badfunc(3)"</span><span class="p">)</span>
</pre></div>
</div>
<p>Exceptions:</p>
<div class="highlight-python"><pre># pysqlite
Traceback (most recent call last):
File "func.py", line 8, in ?
cur.execute("select badfunc(3)")
pysqlite2.dbapi2.OperationalError: user-defined function raised exception
# apsw
Traceback (most recent call last):
File "t.py", line 8, in ?
cur.execute("select badfunc(3)")
File "apsw.c", line 3660, in resetcursor
File "apsw.c", line 1871, in user-defined-scalar-badfunc
File "t.py", line 3, in badfunc
return 1/0</pre>
</div>
</li>
<li><p class="first">APSW has significantly enhanced debuggability. More details are
available than just what is printed out when exceptions happen like
above. See <a class="reference internal" href="exceptions.html#augmentedstacktraces"><em>augmented stack traces</em></a></p>
</li>
<li><p class="first">APSW has <a class="reference internal" href="execution.html#tracing"><em>execution and row tracers</em></a>. pysqlite has no
equivalent to <a class="reference internal" href="execution.html#executiontracer"><em>execution tracers</em></a> and does have
data adaptors which aren’t the same thing as a <a class="reference internal" href="execution.html#rowtracer"><em>row tracer</em></a> (for example you can’t skip rows or add a new column to
each row returned). pysqlite does have a <a class="reference external" href="http://readthedocs.org/docs/pysqlite/en/latest/sqlite3.html#accessing-columns-by-name-instead-of-by-index">row factory</a>
but you can easily emulate that with the row tracer and
<a class="reference internal" href="cursor.html#apsw.Cursor.getdescription" title="apsw.Cursor.getdescription"><tt class="xref py py-meth docutils literal"><span class="pre">Cursor.getdescription()</span></tt></a>.</p>
</li>
<li><p class="first">APSW has an <a class="reference internal" href="execution.html#apswtrace"><em>apswtrace</em></a> utility script that traces
execution and results in your code without having to modify it in
any way. It also outputs summary reports making it easy to see what
your most time consuming queries are, which are most popular etc.</p>
</li>
<li><p class="first">APSW has an exception corresponding to each SQLite error code and
provides the extended error code. pysqlite combines several SQLite
error codes into corresponding DBAPI exceptions. This is a good
example of the difference in approach of the two wrappers.</p>
</li>
<li><p class="first">The APSW test suite is larger and tests more functionality. Code
coverage by the test suite is 99.6%. pysqlite is good at 81% for C
code although there are several places that coverage can be
improved. I haven’t measured code coverage for pysqlite’s Python
code. The consequences of this are that APSW catches issues earlier
and gives far better diagnostics. As an example try returning an
unsupported type from a registered scalar function.</p>
</li>
<li><p class="first">APSW is faster than pysqlite in my testing. Try the
<a class="reference internal" href="benchmarking.html#speedtest"><em>speedtest</em></a> benchmark.</p>
</li>
</ul>
</div>
<div class="section" id="what-pysqlite-does-better">
<h2>What pysqlite does better<a class="headerlink" href="#what-pysqlite-does-better" title="Permalink to this headline">¶</a></h2>
<ul>
<li><p class="first">pysqlite has an <a class="reference external" href="http://readthedocs.org/docs/pysqlite/en/latest/sqlite3.html#using-adapters-to-store-additional-python-types-in-sqlite-databases">adaptor system</a>
that lets you pretend SQLite stores and returns more types than it
really supports. Note that the database won’t be useful in a
non-pysqlite context (eg PHP code looking at the same database isn’t
going to recognise your Point class). You can implement something similar in APSW by intercepting <a class="reference internal" href="cursor.html#apsw.Cursor.execute" title="apsw.Cursor.execute"><tt class="xref py py-meth docutils literal"><span class="pre">Cursor.execute()</span></tt></a> calls
that suitably mangles the bindings going to SQLite and does
something similar to the rows the iterator returns.</p>
</li>
<li><p class="first">pysqlite lets you work with a database that contains invalid Unicode data by
setting a <a class="reference external" href="http://readthedocs.org/docs/pysqlite/en/latest/sqlite3.html#sqlite3.Connection.text_factory">text factory</a>
that deals with the text data.</p>
<p>APSW does not let you put non-Unicode data into the database in the first place and it will
be considered invalid by other tools reading the data (eg Java,
PHP). If you somehow do manage to get non-Unicode data as a SQLite
string, you can cast it to a blob:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="k">for</span> <span class="n">row</span> <span class="ow">in</span> <span class="n">cursor</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span><span class="s">"select CAST(column as BLOB) from table"</span><span class="p">):</span>
<span class="c"># row[0] is buffer (py2) or bytes (py3) here</span>
<span class="n">deal_with_binary_data</span><span class="p">(</span><span class="n">row</span><span class="p">[</span><span class="mi">0</span><span class="p">])</span>
</pre></div>
</div>
</li>
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<li><a class="reference internal" href="#">pysqlite differences</a><ul>
<li><a class="reference internal" href="#what-apsw-does-better">What APSW does better</a></li>
<li><a class="reference internal" href="#what-pysqlite-does-better">What pysqlite does better</a></li>
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