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Release: <span class="version-num">0.9.8</span> | Release Date: October 13, 2014
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<h1>SQLAlchemy 0.9 Documentation</h1>
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<h3><a href="../index.html">SQLAlchemy 0.9 Documentation</a></h3>
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Oracle
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<ul>
<li><a class="reference internal" href="#">Oracle</a><ul>
<li><a class="reference internal" href="#dialect-oracle">Support for the Oracle database.</a></li>
<li><a class="reference internal" href="#connect-arguments">Connect Arguments</a></li>
<li><a class="reference internal" href="#auto-increment-behavior">Auto Increment Behavior</a></li>
<li><a class="reference internal" href="#identifier-casing">Identifier Casing</a></li>
<li><a class="reference internal" href="#limit-offset-support">LIMIT/OFFSET Support</a></li>
<li><a class="reference internal" href="#returning-support">RETURNING Support</a></li>
<li><a class="reference internal" href="#on-update-cascade">ON UPDATE CASCADE</a></li>
<li><a class="reference internal" href="#oracle-8-compatibility">Oracle 8 Compatibility</a></li>
<li><a class="reference internal" href="#synonym-dblink-reflection">Synonym/DBLINK Reflection</a></li>
<li><a class="reference internal" href="#datetime-compatibility">DateTime Compatibility</a></li>
<li><a class="reference internal" href="#oracle-data-types">Oracle Data Types</a></li>
<li><a class="reference internal" href="#module-sqlalchemy.dialects.oracle.cx_oracle">cx_Oracle</a><ul>
<li><a class="reference internal" href="#dialect-oracle-cx_oracle-url">DBAPI</a></li>
<li><a class="reference internal" href="#dialect-oracle-cx_oracle-connect">Connecting</a></li>
<li><a class="reference internal" href="#additional-connect-arguments">Additional Connect Arguments</a></li>
<li><a class="reference internal" href="#unicode">Unicode</a></li>
<li><a class="reference internal" href="#cx-oracle-returning">RETURNING Support</a></li>
<li><a class="reference internal" href="#lob-objects">LOB Objects</a></li>
<li><a class="reference internal" href="#two-phase-transaction-support">Two Phase Transaction Support</a></li>
<li><a class="reference internal" href="#precision-numerics">Precision Numerics</a></li>
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<div class="section" id="module-sqlalchemy.dialects.oracle.base">
<span id="oracle"></span><span id="oracle-toplevel"></span><h1>Oracle<a class="headerlink" href="#module-sqlalchemy.dialects.oracle.base" title="Permalink to this headline">¶</a></h1>
<div class="section" id="dialect-oracle">
<p>Support for the Oracle database.</p>
<h2>DBAPI Support<a class="headerlink" href="#dialect-oracle" title="Permalink to this headline">¶</a></h2>
<p>The following dialect/DBAPI options are available. Please refer to individual DBAPI sections for connect information.<ul class="simple">
<li><a class="reference external" href="#module-sqlalchemy.dialects.oracle.cx_oracle">cx-Oracle</a></li>
<li><a class="reference external" href="#module-sqlalchemy.dialects.oracle.zxjdbc">zxJDBC for Jython</a></li>
</ul>
</p>
</div>
<div class="section" id="connect-arguments">
<h2>Connect Arguments<a class="headerlink" href="#connect-arguments" title="Permalink to this headline">¶</a></h2>
<p>The dialect supports several <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a> arguments
which affect the behavior of the dialect regardless of driver in use.</p>
<ul class="simple">
<li><tt class="docutils literal"><span class="pre">use_ansi</span></tt> - Use ANSI JOIN constructs (see the section on Oracle 8).
Defaults to <tt class="docutils literal"><span class="pre">True</span></tt>. If <tt class="docutils literal"><span class="pre">False</span></tt>, Oracle-8 compatible constructs are used
for joins.</li>
<li><tt class="docutils literal"><span class="pre">optimize_limits</span></tt> - defaults to <tt class="docutils literal"><span class="pre">False</span></tt>. see the section on
LIMIT/OFFSET.</li>
<li><tt class="docutils literal"><span class="pre">use_binds_for_limits</span></tt> - defaults to <tt class="docutils literal"><span class="pre">True</span></tt>. see the section on
LIMIT/OFFSET.</li>
</ul>
</div>
<div class="section" id="auto-increment-behavior">
<h2>Auto Increment Behavior<a class="headerlink" href="#auto-increment-behavior" title="Permalink to this headline">¶</a></h2>
<p>SQLAlchemy Table objects which include integer primary keys are usually
assumed to have “autoincrementing” behavior, meaning they can generate their
own primary key values upon INSERT. Since Oracle has no “autoincrement”
feature, SQLAlchemy relies upon sequences to produce these values. With the
Oracle dialect, <em>a sequence must always be explicitly specified to enable
autoincrement</em>. This is divergent with the majority of documentation
examples which assume the usage of an autoincrement-capable database. To
specify sequences, use the sqlalchemy.schema.Sequence object which is passed
to a Column construct:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">t</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'mytable'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">Sequence</span><span class="p">(</span><span class="s">'id_seq'</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
<span class="n">Column</span><span class="p">(</span><span class="o">...</span><span class="p">),</span> <span class="o">...</span>
<span class="p">)</span></pre></div>
</div>
<p>This step is also required when using table reflection, i.e. autoload=True:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">t</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'mytable'</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span>
<span class="n">Column</span><span class="p">(</span><span class="s">'id'</span><span class="p">,</span> <span class="n">Integer</span><span class="p">,</span> <span class="n">Sequence</span><span class="p">(</span><span class="s">'id_seq'</span><span class="p">),</span> <span class="n">primary_key</span><span class="o">=</span><span class="bp">True</span><span class="p">),</span>
<span class="n">autoload</span><span class="o">=</span><span class="bp">True</span>
<span class="p">)</span></pre></div>
</div>
</div>
<div class="section" id="identifier-casing">
<h2>Identifier Casing<a class="headerlink" href="#identifier-casing" title="Permalink to this headline">¶</a></h2>
<p>In Oracle, the data dictionary represents all case insensitive identifier
names using UPPERCASE text. SQLAlchemy on the other hand considers an
all-lower case identifier name to be case insensitive. The Oracle dialect
converts all case insensitive identifiers to and from those two formats during
schema level communication, such as reflection of tables and indexes. Using
an UPPERCASE name on the SQLAlchemy side indicates a case sensitive
identifier, and SQLAlchemy will quote the name - this will cause mismatches
against data dictionary data received from Oracle, so unless identifier names
have been truly created as case sensitive (i.e. using quoted names), all
lowercase names should be used on the SQLAlchemy side.</p>
</div>
<div class="section" id="limit-offset-support">
<h2>LIMIT/OFFSET Support<a class="headerlink" href="#limit-offset-support" title="Permalink to this headline">¶</a></h2>
<p>Oracle has no support for the LIMIT or OFFSET keywords. SQLAlchemy uses
a wrapped subquery approach in conjunction with ROWNUM. The exact methodology
is taken from
<a class="reference external" href="http://www.oracle.com/technology/oramag/oracle/06-sep/o56asktom.html">http://www.oracle.com/technology/oramag/oracle/06-sep/o56asktom.html</a> .</p>
<p>There are two options which affect its behavior:</p>
<ul class="simple">
<li>the “FIRST ROWS()” optimization keyword is not used by default. To enable
the usage of this optimization directive, specify <tt class="docutils literal"><span class="pre">optimize_limits=True</span></tt>
to <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>.</li>
<li>the values passed for the limit/offset are sent as bound parameters. Some
users have observed that Oracle produces a poor query plan when the values
are sent as binds and not rendered literally. To render the limit/offset
values literally within the SQL statement, specify
<tt class="docutils literal"><span class="pre">use_binds_for_limits=False</span></tt> to <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>.</li>
</ul>
<p>Some users have reported better performance when the entirely different
approach of a window query is used, i.e. ROW_NUMBER() OVER (ORDER BY), to
provide LIMIT/OFFSET (note that the majority of users don’t observe this).
To suit this case the method used for LIMIT/OFFSET can be replaced entirely.
See the recipe at
<a class="reference external" href="http://www.sqlalchemy.org/trac/wiki/UsageRecipes/WindowFunctionsByDefault">http://www.sqlalchemy.org/trac/wiki/UsageRecipes/WindowFunctionsByDefault</a>
which installs a select compiler that overrides the generation of limit/offset
with a window function.</p>
</div>
<div class="section" id="returning-support">
<span id="oracle-returning"></span><h2>RETURNING Support<a class="headerlink" href="#returning-support" title="Permalink to this headline">¶</a></h2>
<p>The Oracle database supports a limited form of RETURNING, in order to retrieve
result sets of matched rows from INSERT, UPDATE and DELETE statements.
Oracle’s RETURNING..INTO syntax only supports one row being returned, as it
relies upon OUT parameters in order to function. In addition, supported
DBAPIs have further limitations (see <a class="reference internal" href="#cx-oracle-returning"><em>RETURNING Support</em></a>).</p>
<p>SQLAlchemy’s “implicit returning” feature, which employs RETURNING within an
INSERT and sometimes an UPDATE statement in order to fetch newly generated
primary key values and other SQL defaults and expressions, is normally enabled
on the Oracle backend. By default, “implicit returning” typically only
fetches the value of a single <tt class="docutils literal"><span class="pre">nextval(some_seq)</span></tt> expression embedded into
an INSERT in order to increment a sequence within an INSERT statement and get
the value back at the same time. To disable this feature across the board,
specify <tt class="docutils literal"><span class="pre">implicit_returning=False</span></tt> to <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">"oracle://scott:tiger@dsn"</span><span class="p">,</span>
<span class="n">implicit_returning</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span></pre></div>
</div>
<p>Implicit returning can also be disabled on a table-by-table basis as a table
option:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="c"># Core Table</span>
<span class="n">my_table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">"my_table"</span><span class="p">,</span> <span class="n">metadata</span><span class="p">,</span> <span class="o">...</span><span class="p">,</span> <span class="n">implicit_returning</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span>
<span class="c"># declarative</span>
<span class="k">class</span> <span class="nc">MyClass</span><span class="p">(</span><span class="n">Base</span><span class="p">):</span>
<span class="n">__tablename__</span> <span class="o">=</span> <span class="s">'my_table'</span>
<span class="n">__table_args__</span> <span class="o">=</span> <span class="p">{</span><span class="s">"implicit_returning"</span><span class="p">:</span> <span class="bp">False</span><span class="p">}</span></pre></div>
</div>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<p class="last"><a class="reference internal" href="#cx-oracle-returning"><em>RETURNING Support</em></a> - additional cx_oracle-specific restrictions on
implicit returning.</p>
</div>
</div>
<div class="section" id="on-update-cascade">
<h2>ON UPDATE CASCADE<a class="headerlink" href="#on-update-cascade" title="Permalink to this headline">¶</a></h2>
<p>Oracle doesn’t have native ON UPDATE CASCADE functionality. A trigger based
solution is available at
<a class="reference external" href="http://asktom.oracle.com/tkyte/update_cascade/index.html">http://asktom.oracle.com/tkyte/update_cascade/index.html</a> .</p>
<p>When using the SQLAlchemy ORM, the ORM has limited ability to manually issue
cascading updates - specify ForeignKey objects using the
“deferrable=True, initially=’deferred’” keyword arguments,
and specify “passive_updates=False” on each relationship().</p>
</div>
<div class="section" id="oracle-8-compatibility">
<h2>Oracle 8 Compatibility<a class="headerlink" href="#oracle-8-compatibility" title="Permalink to this headline">¶</a></h2>
<p>When Oracle 8 is detected, the dialect internally configures itself to the
following behaviors:</p>
<ul class="simple">
<li>the use_ansi flag is set to False. This has the effect of converting all
JOIN phrases into the WHERE clause, and in the case of LEFT OUTER JOIN
makes use of Oracle’s (+) operator.</li>
<li>the NVARCHAR2 and NCLOB datatypes are no longer generated as DDL when
the <a class="reference internal" href="../core/types.html#sqlalchemy.types.Unicode" title="sqlalchemy.types.Unicode"><tt class="xref py py-class docutils literal"><span class="pre">Unicode</span></tt></a> is used - VARCHAR2 and CLOB are
issued instead. This because these types don’t seem to work correctly on
Oracle 8 even though they are available. The
<a class="reference internal" href="../core/types.html#sqlalchemy.types.NVARCHAR" title="sqlalchemy.types.NVARCHAR"><tt class="xref py py-class docutils literal"><span class="pre">NVARCHAR</span></tt></a> and
<a class="reference internal" href="#sqlalchemy.dialects.oracle.NCLOB" title="sqlalchemy.dialects.oracle.NCLOB"><tt class="xref py py-class docutils literal"><span class="pre">NCLOB</span></tt></a> types will always generate
NVARCHAR2 and NCLOB.</li>
<li>the “native unicode” mode is disabled when using cx_oracle, i.e. SQLAlchemy
encodes all Python unicode objects to “string” before passing in as bind
parameters.</li>
</ul>
</div>
<div class="section" id="synonym-dblink-reflection">
<h2>Synonym/DBLINK Reflection<a class="headerlink" href="#synonym-dblink-reflection" title="Permalink to this headline">¶</a></h2>
<p>When using reflection with Table objects, the dialect can optionally search
for tables indicated by synonyms, either in local or remote schemas or
accessed over DBLINK, by passing the flag <tt class="docutils literal"><span class="pre">oracle_resolve_synonyms=True</span></tt> as
a keyword argument to the <a class="reference internal" href="../core/metadata.html#sqlalchemy.schema.Table" title="sqlalchemy.schema.Table"><tt class="xref py py-class docutils literal"><span class="pre">Table</span></tt></a> construct:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">some_table</span> <span class="o">=</span> <span class="n">Table</span><span class="p">(</span><span class="s">'some_table'</span><span class="p">,</span> <span class="n">autoload</span><span class="o">=</span><span class="bp">True</span><span class="p">,</span>
<span class="n">autoload_with</span><span class="o">=</span><span class="n">some_engine</span><span class="p">,</span>
<span class="n">oracle_resolve_synonyms</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span></pre></div>
</div>
<p>When this flag is set, the given name (such as <tt class="docutils literal"><span class="pre">some_table</span></tt> above) will
be searched not just in the <tt class="docutils literal"><span class="pre">ALL_TABLES</span></tt> view, but also within the
<tt class="docutils literal"><span class="pre">ALL_SYNONYMS</span></tt> view to see if this name is actually a synonym to another
name. If the synonym is located and refers to a DBLINK, the oracle dialect
knows how to locate the table’s information using DBLINK syntax(e.g.
<tt class="docutils literal"><span class="pre">@dblink</span></tt>).</p>
<p><tt class="docutils literal"><span class="pre">oracle_resolve_synonyms</span></tt> is accepted wherever reflection arguments are
accepted, including methods such as <a class="reference internal" href="../core/metadata.html#sqlalchemy.schema.MetaData.reflect" title="sqlalchemy.schema.MetaData.reflect"><tt class="xref py py-meth docutils literal"><span class="pre">MetaData.reflect()</span></tt></a> and
<a class="reference internal" href="../core/reflection.html#sqlalchemy.engine.reflection.Inspector.get_columns" title="sqlalchemy.engine.reflection.Inspector.get_columns"><tt class="xref py py-meth docutils literal"><span class="pre">Inspector.get_columns()</span></tt></a>.</p>
<p>If synonyms are not in use, this flag should be left disabled.</p>
</div>
<div class="section" id="datetime-compatibility">
<h2>DateTime Compatibility<a class="headerlink" href="#datetime-compatibility" title="Permalink to this headline">¶</a></h2>
<p>Oracle has no datatype known as <tt class="docutils literal"><span class="pre">DATETIME</span></tt>, it instead has only <tt class="docutils literal"><span class="pre">DATE</span></tt>,
which can actually store a date and time value. For this reason, the Oracle
dialect provides a type <a class="reference internal" href="#sqlalchemy.dialects.oracle.DATE" title="sqlalchemy.dialects.oracle.DATE"><tt class="xref py py-class docutils literal"><span class="pre">oracle.DATE</span></tt></a> which is a subclass of
<a class="reference internal" href="../core/types.html#sqlalchemy.types.DateTime" title="sqlalchemy.types.DateTime"><tt class="xref py py-class docutils literal"><span class="pre">DateTime</span></tt></a>. This type has no special behavior, and is only
present as a “marker” for this type; additionally, when a database column
is reflected and the type is reported as <tt class="docutils literal"><span class="pre">DATE</span></tt>, the time-supporting
<a class="reference internal" href="#sqlalchemy.dialects.oracle.DATE" title="sqlalchemy.dialects.oracle.DATE"><tt class="xref py py-class docutils literal"><span class="pre">oracle.DATE</span></tt></a> type is used.</p>
<div class="versionchanged">
<p><span>Changed in version 0.9.4: </span>Added <a class="reference internal" href="#sqlalchemy.dialects.oracle.DATE" title="sqlalchemy.dialects.oracle.DATE"><tt class="xref py py-class docutils literal"><span class="pre">oracle.DATE</span></tt></a> to subclass
<a class="reference internal" href="../core/types.html#sqlalchemy.types.DateTime" title="sqlalchemy.types.DateTime"><tt class="xref py py-class docutils literal"><span class="pre">DateTime</span></tt></a>. This is a change as previous versions
would reflect a <tt class="docutils literal"><span class="pre">DATE</span></tt> column as <a class="reference internal" href="../core/types.html#sqlalchemy.types.DATE" title="sqlalchemy.types.DATE"><tt class="xref py py-class docutils literal"><span class="pre">types.DATE</span></tt></a>, which subclasses
<a class="reference internal" href="../core/types.html#sqlalchemy.types.Date" title="sqlalchemy.types.Date"><tt class="xref py py-class docutils literal"><span class="pre">Date</span></tt></a>. The only significance here is for schemes that are
examining the type of column for use in special Python translations or
for migrating schemas to other database backends.</p>
</div>
</div>
<div class="section" id="oracle-data-types">
<h2>Oracle Data Types<a class="headerlink" href="#oracle-data-types" title="Permalink to this headline">¶</a></h2>
<p>As with all SQLAlchemy dialects, all UPPERCASE types that are known to be
valid with Oracle are importable from the top level dialect, whether
they originate from <a class="reference internal" href="../core/types.html#module-sqlalchemy.types" title="sqlalchemy.types"><tt class="xref py py-mod docutils literal"><span class="pre">sqlalchemy.types</span></tt></a> or from the local dialect:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">sqlalchemy.dialects.oracle</span> <span class="kn">import</span> \
<span class="n">BFILE</span><span class="p">,</span> <span class="n">BLOB</span><span class="p">,</span> <span class="n">CHAR</span><span class="p">,</span> <span class="n">CLOB</span><span class="p">,</span> <span class="n">DATE</span><span class="p">,</span> \
<span class="n">DOUBLE_PRECISION</span><span class="p">,</span> <span class="n">FLOAT</span><span class="p">,</span> <span class="n">INTERVAL</span><span class="p">,</span> <span class="n">LONG</span><span class="p">,</span> <span class="n">NCLOB</span><span class="p">,</span> \
<span class="n">NUMBER</span><span class="p">,</span> <span class="n">NVARCHAR</span><span class="p">,</span> <span class="n">NVARCHAR2</span><span class="p">,</span> <span class="n">RAW</span><span class="p">,</span> <span class="n">TIMESTAMP</span><span class="p">,</span> <span class="n">VARCHAR</span><span class="p">,</span> \
<span class="n">VARCHAR2</span></pre></div>
</div>
<p>Types which are specific to Oracle, or have Oracle-specific
construction arguments, are as follows:</p>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.BFILE">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">BFILE</tt><big>(</big><em>length=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.BFILE" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.LargeBinary" title="sqlalchemy.types.LargeBinary"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.LargeBinary</span></tt></a></p>
<dl class="method">
<dt id="sqlalchemy.dialects.oracle.BFILE.__init__">
<tt class="descname">__init__</tt><big>(</big><em>length=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.BFILE.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Construct a LargeBinary type.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><span class="target" id="sqlalchemy.dialects.oracle.BFILE.params.length"></span><strong>length</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.BFILE.params.length">¶</a> – optional, a length for the column for use in
DDL statements, for those BLOB types that accept a length
(i.e. MySQL). It does <em>not</em> produce a small BINARY/VARBINARY
type - use the BINARY/VARBINARY types specifically for those.
May be safely omitted if no <tt class="docutils literal"><span class="pre">CREATE</span>
<span class="pre">TABLE</span></tt> will be issued. Certain databases may require a
<em>length</em> for use in DDL, and will raise an exception when
the <tt class="docutils literal"><span class="pre">CREATE</span> <span class="pre">TABLE</span></tt> DDL is issued.</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.DATE">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">DATE</tt><big>(</big><em>timezone=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.DATE" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.DateTime" title="sqlalchemy.types.DateTime"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.DateTime</span></tt></a></p>
<p>Provide the oracle DATE type.</p>
<p>This type has no special Python behavior, except that it subclasses
<a class="reference internal" href="../core/types.html#sqlalchemy.types.DateTime" title="sqlalchemy.types.DateTime"><tt class="xref py py-class docutils literal"><span class="pre">types.DateTime</span></tt></a>; this is to suit the fact that the Oracle
<tt class="docutils literal"><span class="pre">DATE</span></tt> type supports a time value.</p>
<div class="versionadded">
<p><span>New in version 0.9.4.</span></p>
</div>
<dl class="method">
<dt id="sqlalchemy.dialects.oracle.DATE.__init__">
<tt class="descname">__init__</tt><big>(</big><em>timezone=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.DATE.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Construct a new <a class="reference internal" href="../core/types.html#sqlalchemy.types.DateTime" title="sqlalchemy.types.DateTime"><tt class="xref py py-class docutils literal"><span class="pre">DateTime</span></tt></a>.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><span class="target" id="sqlalchemy.dialects.oracle.DATE.params.timezone"></span><strong>timezone</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.DATE.params.timezone">¶</a> – boolean. If True, and supported by the
backend, will produce ‘TIMESTAMP WITH TIMEZONE’. For backends
that don’t support timezone aware timestamps, has no
effect.</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.DOUBLE_PRECISION">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">DOUBLE_PRECISION</tt><big>(</big><em>precision=None</em>, <em>scale=None</em>, <em>asdecimal=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.DOUBLE_PRECISION" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.Numeric" title="sqlalchemy.types.Numeric"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.Numeric</span></tt></a></p>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.INTERVAL">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">INTERVAL</tt><big>(</big><em>day_precision=None</em>, <em>second_precision=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.INTERVAL" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.TypeEngine" title="sqlalchemy.types.TypeEngine"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.TypeEngine</span></tt></a></p>
<dl class="method">
<dt id="sqlalchemy.dialects.oracle.INTERVAL.__init__">
<tt class="descname">__init__</tt><big>(</big><em>day_precision=None</em>, <em>second_precision=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.INTERVAL.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Construct an INTERVAL.</p>
<p>Note that only DAY TO SECOND intervals are currently supported.
This is due to a lack of support for YEAR TO MONTH intervals
within available DBAPIs (cx_oracle and zxjdbc).</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><span class="target" id="sqlalchemy.dialects.oracle.INTERVAL.params.day_precision"></span><strong>day_precision</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.INTERVAL.params.day_precision">¶</a> – the day precision value. this is the number of
digits to store for the day field. Defaults to “2”</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.INTERVAL.params.second_precision"></span><strong>second_precision</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.INTERVAL.params.second_precision">¶</a> – the second precision value. this is the
number of digits to store for the fractional seconds field.
Defaults to “6”.</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.NCLOB">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">NCLOB</tt><big>(</big><em>length=None</em>, <em>collation=None</em>, <em>convert_unicode=False</em>, <em>unicode_error=None</em>, <em>_warn_on_bytestring=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.NCLOB" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.Text" title="sqlalchemy.types.Text"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.Text</span></tt></a></p>
<dl class="method">
<dt id="sqlalchemy.dialects.oracle.NCLOB.__init__">
<tt class="descname">__init__</tt><big>(</big><em>length=None</em>, <em>collation=None</em>, <em>convert_unicode=False</em>, <em>unicode_error=None</em>, <em>_warn_on_bytestring=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.NCLOB.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Create a string-holding type.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><span class="target" id="sqlalchemy.dialects.oracle.NCLOB.params.length"></span><strong>length</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.NCLOB.params.length">¶</a> – optional, a length for the column for use in
DDL and CAST expressions. May be safely omitted if no <tt class="docutils literal"><span class="pre">CREATE</span>
<span class="pre">TABLE</span></tt> will be issued. Certain databases may require a
<tt class="docutils literal"><span class="pre">length</span></tt> for use in DDL, and will raise an exception when
the <tt class="docutils literal"><span class="pre">CREATE</span> <span class="pre">TABLE</span></tt> DDL is issued if a <tt class="docutils literal"><span class="pre">VARCHAR</span></tt>
with no length is included. Whether the value is
interpreted as bytes or characters is database specific.</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.NCLOB.params.collation"></span><strong>collation</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.NCLOB.params.collation">¶</a> – <p>Optional, a column-level collation for
use in DDL and CAST expressions. Renders using the
COLLATE keyword supported by SQLite, MySQL, and Postgresql.
E.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="n">cast</span><span class="p">,</span> <span class="n">select</span><span class="p">,</span> <span class="n">String</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">select</span><span class="p">([</span><span class="n">cast</span><span class="p">(</span><span class="s">'some string'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="n">collation</span><span class="o">=</span><span class="s">'utf8'</span><span class="p">))])</span>
<span class="go">SELECT CAST(:param_1 AS VARCHAR COLLATE utf8) AS anon_1</span></pre></div>
</div>
<div class="versionadded">
<p><span>New in version 0.8: </span>Added support for COLLATE to all
string types.</p>
</div>
</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.NCLOB.params.convert_unicode"></span><strong>convert_unicode</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.NCLOB.params.convert_unicode">¶</a> – <p>When set to <tt class="docutils literal"><span class="pre">True</span></tt>, the
<a class="reference internal" href="../core/types.html#sqlalchemy.types.String" title="sqlalchemy.types.String"><tt class="xref py py-class docutils literal"><span class="pre">String</span></tt></a> type will assume that
input is to be passed as Python <tt class="docutils literal"><span class="pre">unicode</span></tt> objects,
and results returned as Python <tt class="docutils literal"><span class="pre">unicode</span></tt> objects.
If the DBAPI in use does not support Python unicode
(which is fewer and fewer these days), SQLAlchemy
will encode/decode the value, using the
value of the <tt class="docutils literal"><span class="pre">encoding</span></tt> parameter passed to
<a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a> as the encoding.</p>
<p>When using a DBAPI that natively supports Python
unicode objects, this flag generally does not
need to be set. For columns that are explicitly
intended to store non-ASCII data, the <a class="reference internal" href="../core/types.html#sqlalchemy.types.Unicode" title="sqlalchemy.types.Unicode"><tt class="xref py py-class docutils literal"><span class="pre">Unicode</span></tt></a>
or <a class="reference internal" href="../core/types.html#sqlalchemy.types.UnicodeText" title="sqlalchemy.types.UnicodeText"><tt class="xref py py-class docutils literal"><span class="pre">UnicodeText</span></tt></a>
types should be used regardless, which feature
the same behavior of <tt class="docutils literal"><span class="pre">convert_unicode</span></tt> but
also indicate an underlying column type that
directly supports unicode, such as <tt class="docutils literal"><span class="pre">NVARCHAR</span></tt>.</p>
<p>For the extremely rare case that Python <tt class="docutils literal"><span class="pre">unicode</span></tt>
is to be encoded/decoded by SQLAlchemy on a backend
that does natively support Python <tt class="docutils literal"><span class="pre">unicode</span></tt>,
the value <tt class="docutils literal"><span class="pre">force</span></tt> can be passed here which will
cause SQLAlchemy’s encode/decode services to be
used unconditionally.</p>
</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.NCLOB.params.unicode_error"></span><strong>unicode_error</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.NCLOB.params.unicode_error">¶</a> – Optional, a method to use to handle Unicode
conversion errors. Behaves like the <tt class="docutils literal"><span class="pre">errors</span></tt> keyword argument to
the standard library’s <tt class="docutils literal"><span class="pre">string.decode()</span></tt> functions. This flag
requires that <tt class="docutils literal"><span class="pre">convert_unicode</span></tt> is set to <tt class="docutils literal"><span class="pre">force</span></tt> - otherwise,
SQLAlchemy is not guaranteed to handle the task of unicode
conversion. Note that this flag adds significant performance
overhead to row-fetching operations for backends that already
return unicode objects natively (which most DBAPIs do). This
flag should only be used as a last resort for reading
strings from a column with varied or corrupted encodings.</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.NUMBER">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">NUMBER</tt><big>(</big><em>precision=None</em>, <em>scale=None</em>, <em>asdecimal=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.NUMBER" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.Numeric" title="sqlalchemy.types.Numeric"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.Numeric</span></tt></a>, <a class="reference internal" href="../core/types.html#sqlalchemy.types.Integer" title="sqlalchemy.types.Integer"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.Integer</span></tt></a></p>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.LONG">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">LONG</tt><big>(</big><em>length=None</em>, <em>collation=None</em>, <em>convert_unicode=False</em>, <em>unicode_error=None</em>, <em>_warn_on_bytestring=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.LONG" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <a class="reference internal" href="../core/types.html#sqlalchemy.types.Text" title="sqlalchemy.types.Text"><tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types.Text</span></tt></a></p>
<dl class="method">
<dt id="sqlalchemy.dialects.oracle.LONG.__init__">
<tt class="descname">__init__</tt><big>(</big><em>length=None</em>, <em>collation=None</em>, <em>convert_unicode=False</em>, <em>unicode_error=None</em>, <em>_warn_on_bytestring=False</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.LONG.__init__" title="Permalink to this definition">¶</a></dt>
<dd><p>Create a string-holding type.</p>
<table class="docutils field-list" frame="void" rules="none">
<col class="field-name" />
<col class="field-body" />
<tbody valign="top">
<tr class="field-odd field"><th class="field-name">Parameters:</th><td class="field-body"><ul class="first last simple">
<li><span class="target" id="sqlalchemy.dialects.oracle.LONG.params.length"></span><strong>length</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.LONG.params.length">¶</a> – optional, a length for the column for use in
DDL and CAST expressions. May be safely omitted if no <tt class="docutils literal"><span class="pre">CREATE</span>
<span class="pre">TABLE</span></tt> will be issued. Certain databases may require a
<tt class="docutils literal"><span class="pre">length</span></tt> for use in DDL, and will raise an exception when
the <tt class="docutils literal"><span class="pre">CREATE</span> <span class="pre">TABLE</span></tt> DDL is issued if a <tt class="docutils literal"><span class="pre">VARCHAR</span></tt>
with no length is included. Whether the value is
interpreted as bytes or characters is database specific.</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.LONG.params.collation"></span><strong>collation</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.LONG.params.collation">¶</a> – <p>Optional, a column-level collation for
use in DDL and CAST expressions. Renders using the
COLLATE keyword supported by SQLite, MySQL, and Postgresql.
E.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="n">cast</span><span class="p">,</span> <span class="n">select</span><span class="p">,</span> <span class="n">String</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">select</span><span class="p">([</span><span class="n">cast</span><span class="p">(</span><span class="s">'some string'</span><span class="p">,</span> <span class="n">String</span><span class="p">(</span><span class="n">collation</span><span class="o">=</span><span class="s">'utf8'</span><span class="p">))])</span>
<span class="go">SELECT CAST(:param_1 AS VARCHAR COLLATE utf8) AS anon_1</span></pre></div>
</div>
<div class="versionadded">
<p><span>New in version 0.8: </span>Added support for COLLATE to all
string types.</p>
</div>
</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.LONG.params.convert_unicode"></span><strong>convert_unicode</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.LONG.params.convert_unicode">¶</a> – <p>When set to <tt class="docutils literal"><span class="pre">True</span></tt>, the
<a class="reference internal" href="../core/types.html#sqlalchemy.types.String" title="sqlalchemy.types.String"><tt class="xref py py-class docutils literal"><span class="pre">String</span></tt></a> type will assume that
input is to be passed as Python <tt class="docutils literal"><span class="pre">unicode</span></tt> objects,
and results returned as Python <tt class="docutils literal"><span class="pre">unicode</span></tt> objects.
If the DBAPI in use does not support Python unicode
(which is fewer and fewer these days), SQLAlchemy
will encode/decode the value, using the
value of the <tt class="docutils literal"><span class="pre">encoding</span></tt> parameter passed to
<a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a> as the encoding.</p>
<p>When using a DBAPI that natively supports Python
unicode objects, this flag generally does not
need to be set. For columns that are explicitly
intended to store non-ASCII data, the <a class="reference internal" href="../core/types.html#sqlalchemy.types.Unicode" title="sqlalchemy.types.Unicode"><tt class="xref py py-class docutils literal"><span class="pre">Unicode</span></tt></a>
or <a class="reference internal" href="../core/types.html#sqlalchemy.types.UnicodeText" title="sqlalchemy.types.UnicodeText"><tt class="xref py py-class docutils literal"><span class="pre">UnicodeText</span></tt></a>
types should be used regardless, which feature
the same behavior of <tt class="docutils literal"><span class="pre">convert_unicode</span></tt> but
also indicate an underlying column type that
directly supports unicode, such as <tt class="docutils literal"><span class="pre">NVARCHAR</span></tt>.</p>
<p>For the extremely rare case that Python <tt class="docutils literal"><span class="pre">unicode</span></tt>
is to be encoded/decoded by SQLAlchemy on a backend
that does natively support Python <tt class="docutils literal"><span class="pre">unicode</span></tt>,
the value <tt class="docutils literal"><span class="pre">force</span></tt> can be passed here which will
cause SQLAlchemy’s encode/decode services to be
used unconditionally.</p>
</li>
<li><span class="target" id="sqlalchemy.dialects.oracle.LONG.params.unicode_error"></span><strong>unicode_error</strong><a class="paramlink headerlink reference internal" href="#sqlalchemy.dialects.oracle.LONG.params.unicode_error">¶</a> – Optional, a method to use to handle Unicode
conversion errors. Behaves like the <tt class="docutils literal"><span class="pre">errors</span></tt> keyword argument to
the standard library’s <tt class="docutils literal"><span class="pre">string.decode()</span></tt> functions. This flag
requires that <tt class="docutils literal"><span class="pre">convert_unicode</span></tt> is set to <tt class="docutils literal"><span class="pre">force</span></tt> - otherwise,
SQLAlchemy is not guaranteed to handle the task of unicode
conversion. Note that this flag adds significant performance
overhead to row-fetching operations for backends that already
return unicode objects natively (which most DBAPIs do). This
flag should only be used as a last resort for reading
strings from a column with varied or corrupted encodings.</li>
</ul>
</td>
</tr>
</tbody>
</table>
</dd></dl>
</dd></dl>
<dl class="class">
<dt id="sqlalchemy.dialects.oracle.RAW">
<em class="property">class </em><tt class="descclassname">sqlalchemy.dialects.oracle.</tt><tt class="descname">RAW</tt><big>(</big><em>length=None</em><big>)</big><a class="headerlink" href="#sqlalchemy.dialects.oracle.RAW" title="Permalink to this definition">¶</a></dt>
<dd><p>Bases: <tt class="xref py py-class docutils literal"><span class="pre">sqlalchemy.types._Binary</span></tt></p>
</dd></dl>
</div>
<div class="section" id="module-sqlalchemy.dialects.oracle.cx_oracle">
<span id="cx-oracle"></span><h2>cx_Oracle<a class="headerlink" href="#module-sqlalchemy.dialects.oracle.cx_oracle" title="Permalink to this headline">¶</a></h2>
<p>Support for the Oracle database via the cx-Oracle driver.</p>
<div class="section" id="dialect-oracle-cx_oracle-url">
<h3>DBAPI<a class="headerlink" href="#dialect-oracle-cx_oracle-url" title="Permalink to this headline">¶</a></h3>
<p>Documentation and download information (if applicable) for cx-Oracle is available at:
<a class="reference external" href="http://cx-oracle.sourceforge.net/">http://cx-oracle.sourceforge.net/</a></p>
</div>
<div class="section" id="dialect-oracle-cx_oracle-connect">
<h3>Connecting<a class="headerlink" href="#dialect-oracle-cx_oracle-connect" title="Permalink to this headline">¶</a></h3>
<p>Connect String:<div class="highlight-python"><pre>oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]</pre>
</div>
</p>
</div>
<div class="section" id="additional-connect-arguments">
<h3>Additional Connect Arguments<a class="headerlink" href="#additional-connect-arguments" title="Permalink to this headline">¶</a></h3>
<p>When connecting with <tt class="docutils literal"><span class="pre">dbname</span></tt> present, the host, port, and dbname tokens are
converted to a TNS name using
the cx_oracle <tt class="docutils literal"><span class="pre">makedsn()</span></tt> function. Otherwise, the host token is taken
directly as a TNS name.</p>
<p>Additional arguments which may be specified either as query string arguments
on the URL, or as keyword arguments to <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a> are:</p>
<ul>
<li><p class="first"><tt class="docutils literal"><span class="pre">allow_twophase</span></tt> - enable two-phase transactions. Defaults to <tt class="docutils literal"><span class="pre">True</span></tt>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">arraysize</span></tt> - set the cx_oracle.arraysize value on cursors, defaulted
to 50. This setting is significant with cx_Oracle as the contents of LOB
objects are only readable within a “live” row (e.g. within a batch of
50 rows).</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">auto_convert_lobs</span></tt> - defaults to True; See <a class="reference internal" href="#cx-oracle-lob"><em>LOB Objects</em></a>.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">auto_setinputsizes</span></tt> - the cx_oracle.setinputsizes() call is issued for
all bind parameters. This is required for LOB datatypes but can be
disabled to reduce overhead. Defaults to <tt class="docutils literal"><span class="pre">True</span></tt>. Specific types
can be excluded from this process using the <tt class="docutils literal"><span class="pre">exclude_setinputsizes</span></tt>
parameter.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">coerce_to_unicode</span></tt> - see <a class="reference internal" href="#cx-oracle-unicode"><em>Unicode</em></a> for detail.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">coerce_to_decimal</span></tt> - see <a class="reference internal" href="#cx-oracle-numeric"><em>Precision Numerics</em></a> for detail.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">exclude_setinputsizes</span></tt> - a tuple or list of string DBAPI type names to
be excluded from the “auto setinputsizes” feature. The type names here
must match DBAPI types that are found in the “cx_Oracle” module namespace,
such as cx_Oracle.UNICODE, cx_Oracle.NCLOB, etc. Defaults to
<tt class="docutils literal"><span class="pre">(STRING,</span> <span class="pre">UNICODE)</span></tt>.</p>
<div class="versionadded">
<p><span>New in version 0.8: </span>specific DBAPI types can be excluded from the
auto_setinputsizes feature via the exclude_setinputsizes attribute.</p>
</div>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">mode</span></tt> - This is given the string value of SYSDBA or SYSOPER, or
alternatively an integer value. This value is only available as a URL query
string argument.</p>
</li>
<li><p class="first"><tt class="docutils literal"><span class="pre">threaded</span></tt> - enable multithreaded access to cx_oracle connections.
Defaults to <tt class="docutils literal"><span class="pre">True</span></tt>. Note that this is the opposite default of the
cx_Oracle DBAPI itself.</p>
</li>
</ul>
</div>
<div class="section" id="unicode">
<span id="cx-oracle-unicode"></span><h3>Unicode<a class="headerlink" href="#unicode" title="Permalink to this headline">¶</a></h3>
<p>The cx_Oracle DBAPI as of version 5 fully supports unicode, and has the
ability to return string results as Python unicode objects natively.</p>
<p>When used in Python 3, cx_Oracle returns all strings as Python unicode objects
(that is, plain <tt class="docutils literal"><span class="pre">str</span></tt> in Python 3). In Python 2, it will return as Python
unicode those column values that are of type <tt class="docutils literal"><span class="pre">NVARCHAR</span></tt> or <tt class="docutils literal"><span class="pre">NCLOB</span></tt>. For
column values that are of type <tt class="docutils literal"><span class="pre">VARCHAR</span></tt> or other non-unicode string types,
it will return values as Python strings (e.g. bytestrings).</p>
<p>The cx_Oracle SQLAlchemy dialect presents two different options for the use
case of returning <tt class="docutils literal"><span class="pre">VARCHAR</span></tt> column values as Python unicode objects under
Python 2:</p>
<ul class="simple">
<li>the cx_Oracle DBAPI has the ability to coerce all string results to Python
unicode objects unconditionally using output type handlers. This has
the advantage that the unicode conversion is global to all statements
at the cx_Oracle driver level, meaning it works with raw textual SQL
statements that have no typing information associated. However, this system
has been observed to incur signfiicant performance overhead, not only
because it takes effect for all string values unconditionally, but also
because cx_Oracle under Python 2 seems to use a pure-Python function call in
order to do the decode operation, which under cPython can orders of
magnitude slower than doing it using C functions alone.</li>
<li>SQLAlchemy has unicode-decoding services built in, and when using
SQLAlchemy’s C extensions, these functions do not use any Python function
calls and are very fast. The disadvantage to this approach is that the
unicode conversion only takes effect for statements where the
<a class="reference internal" href="../core/types.html#sqlalchemy.types.Unicode" title="sqlalchemy.types.Unicode"><tt class="xref py py-class docutils literal"><span class="pre">Unicode</span></tt></a> type or <a class="reference internal" href="../core/types.html#sqlalchemy.types.String" title="sqlalchemy.types.String"><tt class="xref py py-class docutils literal"><span class="pre">String</span></tt></a> type with
<tt class="docutils literal"><span class="pre">convert_unicode=True</span></tt> is explicitly associated with the result column.
This is the case for any ORM or Core query or SQL expression as well as for
a <a class="reference internal" href="../core/sqlelement.html#sqlalchemy.sql.expression.text" title="sqlalchemy.sql.expression.text"><tt class="xref py py-func docutils literal"><span class="pre">text()</span></tt></a> construct that specifies output column types, so in the vast
majority of cases this is not an issue. However, when sending a completely
raw string to <a class="reference internal" href="../core/connections.html#sqlalchemy.engine.Connection.execute" title="sqlalchemy.engine.Connection.execute"><tt class="xref py py-meth docutils literal"><span class="pre">Connection.execute()</span></tt></a>, this typing information isn’t
present, unless the string is handled within a <a class="reference internal" href="../core/sqlelement.html#sqlalchemy.sql.expression.text" title="sqlalchemy.sql.expression.text"><tt class="xref py py-func docutils literal"><span class="pre">text()</span></tt></a> construct that
adds typing information.</li>
</ul>
<p>As of version 0.9.2 of SQLAlchemy, the default approach is to use SQLAlchemy’s
typing system. This keeps cx_Oracle’s expensive Python 2 approach
disabled unless the user explicitly wants it. Under Python 3, SQLAlchemy
detects that cx_Oracle is returning unicode objects natively and cx_Oracle’s
system is used.</p>
<p>To re-enable cx_Oracle’s output type handler under Python 2, the
<tt class="docutils literal"><span class="pre">coerce_to_unicode=True</span></tt> flag (new in 0.9.4) can be passed to
<a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">"oracle+cx_oracle://dsn"</span><span class="p">,</span> <span class="n">coerce_to_unicode</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span></pre></div>
</div>
<p>Alternatively, to run a pure string SQL statement and get <tt class="docutils literal"><span class="pre">VARCHAR</span></tt> results
as Python unicode under Python 2 without using cx_Oracle’s native handlers,
the <a class="reference internal" href="../core/sqlelement.html#sqlalchemy.sql.expression.text" title="sqlalchemy.sql.expression.text"><tt class="xref py py-func docutils literal"><span class="pre">text()</span></tt></a> feature can be used:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">sqlalchemy</span> <span class="kn">import</span> <span class="n">text</span><span class="p">,</span> <span class="n">Unicode</span>
<span class="n">result</span> <span class="o">=</span> <span class="n">conn</span><span class="o">.</span><span class="n">execute</span><span class="p">(</span>
<span class="n">text</span><span class="p">(</span><span class="s">"select username from user"</span><span class="p">)</span><span class="o">.</span><span class="n">columns</span><span class="p">(</span><span class="n">username</span><span class="o">=</span><span class="n">Unicode</span><span class="p">))</span></pre></div>
</div>
<div class="versionchanged">
<p><span>Changed in version 0.9.2: </span>cx_Oracle’s outputtypehandlers are no longer used
for unicode results of non-unicode datatypes in Python 2, after they were
identified as a major performance bottleneck. SQLAlchemy’s own unicode
facilities are used instead.</p>
</div>
<div class="versionadded">
<p><span>New in version 0.9.4: </span>Added the <tt class="docutils literal"><span class="pre">coerce_to_unicode</span></tt> flag, to re-enable
cx_Oracle’s outputtypehandler and revert to pre-0.9.2 behavior.</p>
</div>
</div>
<div class="section" id="cx-oracle-returning">
<span id="id1"></span><h3>RETURNING Support<a class="headerlink" href="#cx-oracle-returning" title="Permalink to this headline">¶</a></h3>
<p>The cx_oracle DBAPI supports a limited subset of Oracle’s already limited
RETURNING support. Typically, results can only be guaranteed for at most one
column being returned; this is the typical case when SQLAlchemy uses RETURNING
to get just the value of a primary-key-associated sequence value.
Additional column expressions will cause problems in a non-determinative way,
due to cx_oracle’s lack of support for the OCI_DATA_AT_EXEC API which is
required for more complex RETURNING scenarios.</p>
<p>For this reason, stability may be enhanced by disabling RETURNING support
completely; SQLAlchemy otherwise will use RETURNING to fetch newly
sequence-generated primary keys. As illustrated in <a class="reference internal" href="#oracle-returning"><em>RETURNING Support</em></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">"oracle://scott:tiger@dsn"</span><span class="p">,</span>
<span class="n">implicit_returning</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span></pre></div>
</div>
<div class="admonition seealso">
<p class="first admonition-title">See also</p>
<p><a class="reference external" href="http://docs.oracle.com/cd/B10501_01/appdev.920/a96584/oci05bnd.htm#420693">http://docs.oracle.com/cd/B10501_01/appdev.920/a96584/oci05bnd.htm#420693</a>
- OCI documentation for RETURNING</p>
<p class="last"><a class="reference external" href="http://sourceforge.net/mailarchive/message.php?msg_id=31338136">http://sourceforge.net/mailarchive/message.php?msg_id=31338136</a>
- cx_oracle developer commentary</p>
</div>
</div>
<div class="section" id="lob-objects">
<span id="cx-oracle-lob"></span><h3>LOB Objects<a class="headerlink" href="#lob-objects" title="Permalink to this headline">¶</a></h3>
<p>cx_oracle returns oracle LOBs using the cx_oracle.LOB object. SQLAlchemy
converts these to strings so that the interface of the Binary type is
consistent with that of other backends, and so that the linkage to a live
cursor is not needed in scenarios like result.fetchmany() and
result.fetchall(). This means that by default, LOB objects are fully fetched
unconditionally by SQLAlchemy, and the linkage to a live cursor is broken.</p>
<p>To disable this processing, pass <tt class="docutils literal"><span class="pre">auto_convert_lobs=False</span></tt> to
<a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>.</p>
</div>
<div class="section" id="two-phase-transaction-support">
<h3>Two Phase Transaction Support<a class="headerlink" href="#two-phase-transaction-support" title="Permalink to this headline">¶</a></h3>
<p>Two Phase transactions are implemented using XA transactions, and are known
to work in a rudimental fashion with recent versions of cx_Oracle
as of SQLAlchemy 0.8.0b2, 0.7.10. However, the mechanism is not yet
considered to be robust and should still be regarded as experimental.</p>
<p>In particular, the cx_Oracle DBAPI as recently as 5.1.2 has a bug regarding
two phase which prevents
a particular DBAPI connection from being consistently usable in both
prepared transactions as well as traditional DBAPI usage patterns; therefore
once a particular connection is used via <tt class="xref py py-meth docutils literal"><span class="pre">Connection.begin_prepared()</span></tt>,
all subsequent usages of the underlying DBAPI connection must be within
the context of prepared transactions.</p>
<p>The default behavior of <a class="reference internal" href="../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><tt class="xref py py-class docutils literal"><span class="pre">Engine</span></tt></a> is to maintain a pool of DBAPI
connections. Therefore, due to the above glitch, a DBAPI connection that has
been used in a two-phase operation, and is then returned to the pool, will
not be usable in a non-two-phase context. To avoid this situation,
the application can make one of several choices:</p>
<ul class="simple">
<li>Disable connection pooling using <a class="reference internal" href="../core/pooling.html#sqlalchemy.pool.NullPool" title="sqlalchemy.pool.NullPool"><tt class="xref py py-class docutils literal"><span class="pre">NullPool</span></tt></a></li>
<li>Ensure that the particular <a class="reference internal" href="../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><tt class="xref py py-class docutils literal"><span class="pre">Engine</span></tt></a> in use is only used
for two-phase operations. A <a class="reference internal" href="../core/connections.html#sqlalchemy.engine.Engine" title="sqlalchemy.engine.Engine"><tt class="xref py py-class docutils literal"><span class="pre">Engine</span></tt></a> bound to an ORM
<a class="reference internal" href="../orm/session.html#sqlalchemy.orm.session.Session" title="sqlalchemy.orm.session.Session"><tt class="xref py py-class docutils literal"><span class="pre">Session</span></tt></a> which includes <tt class="docutils literal"><span class="pre">twophase=True</span></tt> will consistently
use the two-phase transaction style.</li>
<li>For ad-hoc two-phase operations without disabling pooling, the DBAPI
connection in use can be evicted from the connection pool using the
<a class="reference internal" href="../core/connections.html#sqlalchemy.engine.Connection.detach" title="sqlalchemy.engine.Connection.detach"><tt class="xref py py-meth docutils literal"><span class="pre">Connection.detach()</span></tt></a> method.</li>
</ul>
<div class="versionchanged">
<p><span>Changed in version 0.8.0b2,0.7.10: </span>Support for cx_oracle prepared transactions has been implemented
and tested.</p>
</div>
</div>
<div class="section" id="precision-numerics">
<span id="cx-oracle-numeric"></span><h3>Precision Numerics<a class="headerlink" href="#precision-numerics" title="Permalink to this headline">¶</a></h3>
<p>The SQLAlchemy dialect goes through a lot of steps to ensure
that decimal numbers are sent and received with full accuracy.
An “outputtypehandler” callable is associated with each
cx_oracle connection object which detects numeric types and
receives them as string values, instead of receiving a Python
<tt class="docutils literal"><span class="pre">float</span></tt> directly, which is then passed to the Python
<tt class="docutils literal"><span class="pre">Decimal</span></tt> constructor. The <a class="reference internal" href="../core/types.html#sqlalchemy.types.Numeric" title="sqlalchemy.types.Numeric"><tt class="xref py py-class docutils literal"><span class="pre">Numeric</span></tt></a> and
<a class="reference internal" href="../core/types.html#sqlalchemy.types.Float" title="sqlalchemy.types.Float"><tt class="xref py py-class docutils literal"><span class="pre">Float</span></tt></a> types under the cx_oracle dialect are aware of
this behavior, and will coerce the <tt class="docutils literal"><span class="pre">Decimal</span></tt> to <tt class="docutils literal"><span class="pre">float</span></tt> if
the <tt class="docutils literal"><span class="pre">asdecimal</span></tt> flag is <tt class="docutils literal"><span class="pre">False</span></tt> (default on <a class="reference internal" href="../core/types.html#sqlalchemy.types.Float" title="sqlalchemy.types.Float"><tt class="xref py py-class docutils literal"><span class="pre">Float</span></tt></a>,
optional on <a class="reference internal" href="../core/types.html#sqlalchemy.types.Numeric" title="sqlalchemy.types.Numeric"><tt class="xref py py-class docutils literal"><span class="pre">Numeric</span></tt></a>).</p>
<p>Because the handler coerces to <tt class="docutils literal"><span class="pre">Decimal</span></tt> in all cases first,
the feature can detract significantly from performance.
If precision numerics aren’t required, the decimal handling
can be disabled by passing the flag <tt class="docutils literal"><span class="pre">coerce_to_decimal=False</span></tt>
to <a class="reference internal" href="../core/engines.html#sqlalchemy.create_engine" title="sqlalchemy.create_engine"><tt class="xref py py-func docutils literal"><span class="pre">create_engine()</span></tt></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">engine</span> <span class="o">=</span> <span class="n">create_engine</span><span class="p">(</span><span class="s">"oracle+cx_oracle://dsn"</span><span class="p">,</span> <span class="n">coerce_to_decimal</span><span class="o">=</span><span class="bp">False</span><span class="p">)</span></pre></div>
</div>
<div class="versionadded">
<p><span>New in version 0.7.6: </span>Add the <tt class="docutils literal"><span class="pre">coerce_to_decimal</span></tt> flag.</p>
</div>
<p>Another alternative to performance is to use the
<a class="reference external" href="http://pypi.python.org/pypi/cdecimal/">cdecimal</a> library;
see <a class="reference internal" href="../core/types.html#sqlalchemy.types.Numeric" title="sqlalchemy.types.Numeric"><tt class="xref py py-class docutils literal"><span class="pre">Numeric</span></tt></a> for additional notes.</p>
<p>The handler attempts to use the “precision” and “scale”
attributes of the result set column to best determine if
subsequent incoming values should be received as <tt class="docutils literal"><span class="pre">Decimal</span></tt> as
opposed to int (in which case no processing is added). There are
several scenarios where <a class="reference external" href="http://www.oracle.com/technetwork/database/features/oci/index.html">OCI</a> does not provide unambiguous data
as to the numeric type, including some situations where
individual rows may return a combination of floating point and
integer values. Certain values for “precision” and “scale” have
been observed to determine this scenario. When it occurs, the
outputtypehandler receives as string and then passes off to a
processing function which detects, for each returned value, if a
decimal point is present, and if so converts to <tt class="docutils literal"><span class="pre">Decimal</span></tt>,
otherwise to int. The intention is that simple int-based
statements like “SELECT my_seq.nextval() FROM DUAL” continue to
return ints and not <tt class="docutils literal"><span class="pre">Decimal</span></tt> objects, and that any kind of
floating point value is received as a string so that there is no
floating point loss of precision.</p>
<p>The “decimal point is present” logic itself is also sensitive to
locale. Under <a class="reference external" href="http://www.oracle.com/technetwork/database/features/oci/index.html">OCI</a>, this is controlled by the NLS_LANG
environment variable. Upon first connection, the dialect runs a
test to determine the current “decimal” character, which can be
a comma ”,” for European locales. From that point forward the
outputtypehandler uses that character to represent a decimal
point. Note that cx_oracle 5.0.3 or greater is required
when dealing with numerics with locale settings that don’t use
a period ”.” as the decimal character.</p>
<div class="versionchanged">
<p><span>Changed in version 0.6.6: </span>The outputtypehandler supports the case where the locale uses a
comma ”,” character to represent a decimal point.</p>
</div>
</div>
</div>
<div class="section" id="module-sqlalchemy.dialects.oracle.zxjdbc">
<span id="zxjdbc"></span><h2>zxjdbc<a class="headerlink" href="#module-sqlalchemy.dialects.oracle.zxjdbc" title="Permalink to this headline">¶</a></h2>
<p>Support for the Oracle database via the zxJDBC for Jython driver.</p>
<div class="section" id="dialect-oracle-zxjdbc-url">
<h3>DBAPI<a class="headerlink" href="#dialect-oracle-zxjdbc-url" title="Permalink to this headline">¶</a></h3>
<p>Drivers for this database are available at:
<a class="reference external" href="http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/index.html.">http://www.oracle.com/technology/software/tech/java/sqlj_jdbc/index.html.</a></p>
</div>
<div class="section" id="dialect-oracle-zxjdbc-connect">
<h3>Connecting<a class="headerlink" href="#dialect-oracle-zxjdbc-connect" title="Permalink to this headline">¶</a></h3>
<p>Connect String:<div class="highlight-python"><pre>oracle+zxjdbc://user:pass@host/dbname</pre>
</div>
</p>
</div>
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