Python extension module for bidirectional hstore to dictionary conversion in PL/Python
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This is pyhstore, a Python extension module that allows bidirectional transformation between PostgreSQL hstore and Python dictionary objects in PL/Python, the PostgreSQL embedded Python programming language. To build it you will need the Python and PostgreSQL development headers, as well as the header file for the hstore module. It has been tested on PostgreSQL 9.0 and Python 2.6, but should work on earlier versions. It will not work for Python 3. The easiest way to build and install pyhstore is: $ python setup.py build_py $ python setup.py build_ext -I $(pg_config --includedir-server):/usr/src/postgresql-x.x.x/contrib/hstore $ sudo python setup.py install After these steps check if you have correctly installed pyhstore, by connecting to your database and issuing as a superuser: =# do 'import pyhstore' language plpythonu; If the second command completed successfully, you're done with the installation. If not make sure that your server's PYTHONPATH includes the path where extension modules are installed. Using pyhstore ============== You use pyhstore inside your PL/Python functions to serialise and unserialise hstores from dictionaries. The serialisation functions actually accept and output text, but in the format that can then be interpreted by PostgreSQL as hstores. The module itself is a stopgap solution to enable easier hstore usage until PL/Python gets native hstore handling abilities. And example of using pyhstore in PL/Python would be: CREATE FUNCTION hstore_xform(h hstore) RETURNS hstore AS $$ import pyhstore d = pyhstore.parse_hstore(h) total = 0 for key, val in d.items(): v = int(val) total += v d[key] = str(2 * v) d["total"] = str(total) return pyhstore.serialize_hstore(d) $$ LANGUAGE plpythonu; select * from hstore_xform('John => 10, Mary => 30, Tom => 100'); The output will be a hstore with the value '"Tom"=>"200", "John"=>"20", "Mary"=>"60", "total"=>"140"'. The module is distributed under the MIT License. You can contact the author, Jan Urbanski, at firstname.lastname@example.org.