<!-- $Header: /cvsroot/pgsql/doc/src/sgml/plpython.sgml,v 1.2 2001/09/10 21:58:47 petere Exp $ -->

<!-- $Header: /cvsroot/pgsql/doc/src/sgml/plpython.sgml,v 1.3 2001/09/12 03:58:15 momjian Exp $ -->

<chapter id="plpython">

<title>PL/Python - Python Procedural Language</title>

The global dictionary SD is available to store data between

function calls. This variable is private static data. The global

dictionary GD is public data, available to all python functions

within a backend. Use with care. When the function is used in a

trigger, the triggers tuples are in <literal>TD["new"]</literal> and/or <literal>TD["old"]</literal>

depending on the trigger event. Return 'None' or "OK" from the

python function to indicate the tuple is unmodified, "SKIP" to

abort the event, or "MODIFIED" to indicate you've modified the

tuple. If the trigger was called with arguments they are available

in <literal>TD["args"][0] to TD["args"][(n -1)]</literal>.

within a backend. Use with care.

</para>

<para>

dictionary, as mentioned above.

</para>

</para>

When a function is used in a trigger, the dictionary TD contains

transaction related values. The trigger tuples are in TD["new"]

and/or TD["old"] depending on the trigger event. TD["event"]

contains the event as a string ("INSERT", "UPDATE", "DELETE", or

"UNKNOWN"). TD["when"] contains one of ("BEFORE", "AFTER", or

"UNKNOWN"). TD["level"] contains one of ("ROW", "STATEMENT", or

"UNKNOWN"). TD["name"] contains the trigger name, and TD["relid"]

contains the relation id of the table on which the trigger occurred.

If the trigger was called with arguments they are available

in TD["args"][0] to TD["args"][(n -1)]

</para>

<para>

If the trigger 'when' is "BEFORE", you may Return 'None' or "OK"

from the python function to indicate the tuple is unmodified,

"SKIP" to abort the event, or "MODIFIED" to indicate you've

modified the tuple.

</para>

<para>

The PL/Python language module automatically imports a Python module

called <literal>plpy</literal>. The functions and constants in