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<h1>SQLAlchemy 0.7 Documentation</h1>
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Release: <span class="version-num">0.7.9</span> | Release Date: October 1, 2012
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| <a href="../_sources/dialects/maxdb.txt">view source
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<h3><a href="../index.html">Table of Contents</a></h3>
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<li><a class="reference internal" href="#">MaxDB</a><ul>
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<li><a class="reference internal" href="#overview">Overview</a></li>
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<li><a class="reference internal" href="#connecting">Connecting</a></li>
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<li><a class="reference internal" href="#implementation-notes">Implementation Notes</a><ul>
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<li><a class="reference internal" href="#sapdb-dbapi">sapdb.dbapi</a></li>
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<div class="section" id="module-sqlalchemy.dialects.maxdb.base">
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<span id="maxdb"></span><span id="maxdb-toplevel"></span><h1>MaxDB<a class="headerlink" href="#module-sqlalchemy.dialects.maxdb.base" title="Permalink to this headline">¶</a></h1>
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<p>Support for the MaxDB database.</p>
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<div class="admonition note">
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<p class="first admonition-title">Note</p>
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<p class="last">The MaxDB dialect is <strong>non-functional as of SQLAlchemy 0.6</strong>,
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pending development efforts to bring it up-to-date.</p>
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<div class="section" id="overview">
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<h2>Overview<a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
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<p>The <tt class="docutils literal"><span class="pre">maxdb</span></tt> dialect is <strong>experimental</strong> and has only been tested on 7.6.03.007
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and 7.6.00.037. Of these, <strong>only 7.6.03.007 will work</strong> with SQLAlchemy’s ORM.
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The earlier version has severe <tt class="docutils literal"><span class="pre">LEFT</span> <span class="pre">JOIN</span></tt> limitations and will return
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incorrect results from even very simple ORM queries.</p>
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<p>Only the native Python DB-API is currently supported. ODBC driver support
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is a future enhancement.</p>
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<div class="section" id="connecting">
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<h2>Connecting<a class="headerlink" href="#connecting" title="Permalink to this headline">¶</a></h2>
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<p>The username is case-sensitive. If you usually connect to the
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database with sqlcli and other tools in lower case, you likely need to
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use upper case for DB-API.</p>
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<div class="section" id="implementation-notes">
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<h2>Implementation Notes<a class="headerlink" href="#implementation-notes" title="Permalink to this headline">¶</a></h2>
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<p>With the 7.6.00.37 driver and Python 2.5, it seems that all DB-API
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generated exceptions are broken and can cause Python to crash.</p>
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<p>For ‘somecol.in_([])’ to work, the IN operator’s generation must be changed
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to cast ‘NULL’ to a numeric, i.e. NUM(NULL). The DB-API doesn’t accept a
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bind parameter there, so that particular generation must inline the NULL value,
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which depends on [ticket:807].</p>
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<p>The DB-API is very picky about where bind params may be used in queries.</p>
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<p>Bind params for some functions (e.g. MOD) need type information supplied.
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The dialect does not yet do this automatically.</p>
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<p>Max will occasionally throw up ‘bad sql, compile again’ exceptions for
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perfectly valid SQL. The dialect does not currently handle these, more
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research is needed.</p>
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<p>MaxDB 7.5 and Sap DB <= 7.4 reportedly do not support schemas. A very
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slightly different version of this dialect would be required to support
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those versions, and can easily be added if there is demand. Some other
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required components such as an Max-aware ‘old oracle style’ join compiler
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(thetas with (+) outer indicators) are already done and available for
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integration- email the devel list if you’re interested in working on
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<p>Versions tested: 7.6.03.07 and 7.6.00.37, native Python DB-API</p>
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<li>MaxDB has severe limitations on OUTER JOINs, which are essential to ORM
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eager loading. And rather than raise an error if a SELECT can’t be serviced,
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the database simply returns incorrect results.</li>
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<li>Version 7.6.03.07 seems to JOIN properly, however the docs do not show the
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OUTER restrictions being lifted (as of this writing), and no changelog is
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available to confirm either. If you are using a different server version and
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your tasks require the ORM or any semi-advanced SQL through the SQL layer,
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running the SQLAlchemy test suite against your database is HIGHLY
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recommended before you begin.</li>
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<li>Version 7.6.00.37 is LHS/RHS sensitive in <cite>FROM lhs LEFT OUTER JOIN rhs ON
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lhs.col=rhs.col</cite> vs <cite>rhs.col=lhs.col</cite>!</li>
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<li>Version 7.6.00.37 is confused by <cite>SELECT DISTINCT col as alias FROM t ORDER
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BY col</cite> - these aliased, DISTINCT, ordered queries need to be re-written to
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order by the alias name.</li>
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<li>Version 7.6.x supports creating a SAVEPOINT but not its RELEASE.</li>
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<li>MaxDB supports autoincrement-style columns (DEFAULT SERIAL) and independent
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sequences. When including a DEFAULT SERIAL column in an insert, 0 needs to
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be inserted rather than NULL to generate a value.</li>
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<li>MaxDB supports ANSI and “old Oracle style” theta joins with (+) outer join
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<li>The SQLAlchemy dialect is schema-aware and probably won’t function correctly
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on server versions (pre-7.6?). Support for schema-less server versions could
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be added if there’s call.</li>
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<li>ORDER BY is not supported in subqueries. LIMIT is not supported in
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subqueries. In 7.6.00.37, TOP does work in subqueries, but without limit not
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so useful. OFFSET does not work in 7.6 despite being in the docs. Row number
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tricks in WHERE via ROWNO may be possible but it only seems to allow
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less-than comparison!</li>
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<li>Version 7.6.03.07 can’t LIMIT if a derived table is in FROM: <cite>SELECT * FROM
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(SELECT * FROM a) LIMIT 2</cite></li>
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<li>MaxDB does not support sql’s CAST and can only usefullly cast two types.
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There isn’t much implicit type conversion, so be precise when creating
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<cite>PassiveDefaults</cite> in DDL generation: <cite>‘3’</cite> and <cite>3</cite> aren’t the same.</li>
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<div class="section" id="sapdb-dbapi">
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<h3>sapdb.dbapi<a class="headerlink" href="#sapdb-dbapi" title="Permalink to this headline">¶</a></h3>
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<li>As of 2007-10-22 the Python 2.4 and 2.5 compatible versions of the DB-API
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are no longer available. A forum posting at SAP states that the Python
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driver will be available again “in the future”. The last release from MySQL
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AB works if you can find it.</li>
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<li>sequence.NEXTVAL skips every other value!</li>
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<li>No rowcount for executemany()</li>
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<li>If an INSERT into a table with a DEFAULT SERIAL column inserts the results
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of a function <cite>INSERT INTO t VALUES (LENGTH(‘foo’))</cite>, the cursor won’t have
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the serial id. It needs to be manually yanked from tablename.CURRVAL.</li>
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<li>Super-duper picky about where bind params can be placed. Not smart about
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converting Python types for some functions, such as <cite>MOD(5, ?)</cite>.</li>
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<li>LONG (text, binary) values in result sets are read-once. The dialect uses a
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caching RowProxy when these types are present.</li>
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<li>Connection objects seem like they want to be either <a href="#id1"><span class="problematic" id="id2">`</span></a>close()`d or garbage
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collected, but not both. There’s a warning issued but it seems harmless.</li>
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