Editorial improvements for recent plpython doc updates.
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Tom Lane
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<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.34 2006/10/16 17:28:03 momjian Exp $ -->
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<!-- $PostgreSQL: pgsql/doc/src/sgml/plpython.sgml,v 1.35 2006/10/21 18:33:05 tgl Exp $ -->
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<chapter id="plpython">
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<title>PL/Python - Python Procedural Language</title>
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@ -61,11 +61,11 @@ $$ LANGUAGE plpythonu;
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<para>
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The body of a function is simply a Python script. When the function
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is called, all unnamed arguments are passed as elements to the array
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<varname>args[]</varname> and named arguments as ordinary variables to the
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Python script. The result is returned from the Python code in the usual way,
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with <literal>return</literal> or <literal>yield</literal> (in case of
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a resultset statement).
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is called, its arguments are passed as elements of the array
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<varname>args[]</varname>; named arguments are also passed as ordinary
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variables to the Python script. The result is returned from the Python code
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in the usual way, with <literal>return</literal> or
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<literal>yield</literal> (in case of a resultset statement).
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</para>
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<para>
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@ -101,9 +101,9 @@ def __plpython_procedure_pymax_23456():
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the global <varname>args</varname> list. In the
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<function>pymax</function> example, <varname>args[0]</varname> contains
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whatever was passed in as the first argument and
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<varname>args[1]</varname> contains the second argument's value. Alternatively,
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one can use named parameters as shown in the example above. This greatly simplifies
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the reading and writing of <application>PL/Python</application> code.
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<varname>args[1]</varname> contains the second argument's
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value. Alternatively, one can use named parameters as shown in the example
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above. Use of named parameters is usually more readable.
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</para>
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<para>
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@ -161,31 +161,27 @@ $$ LANGUAGE plpythonu;
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<para>
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There are multiple ways to return row or composite types from a Python
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scripts. In following examples we assume to have:
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function. The following examples assume we have:
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<programlisting>
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CREATE TABLE named_value (
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name text,
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value integer
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);
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</programlisting>
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or
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<programlisting>
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CREATE TYPE named_value AS (
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name text,
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value integer
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);
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</programlisting>
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A composite result can be returned as a:
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<variablelist>
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<varlistentry>
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<term>Sequence types (tuple or list), but not <literal>set</literal> (because
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<term>Sequence type (a tuple or list, but not a set because
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it is not indexable)</term>
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<listitem>
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<para>
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Returned sequence objects must have the same number of items as
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composite types have fields. Item with index 0 is assigned to the first field
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of the composite type, 1 to second and so on. For example:
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Returned sequence objects must have the same number of items as the
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composite result type has fields. The item with index 0 is assigned to
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the first field of the composite type, 1 to the second and so on. For
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example:
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<programlisting>
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CREATE FUNCTION make_pair (name text, value integer)
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@ -196,7 +192,7 @@ AS $$
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$$ LANGUAGE plpythonu;
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</programlisting>
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To return SQL null in any column, insert <symbol>None</symbol> at
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To return a SQL null for any column, insert <symbol>None</symbol> at
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the corresponding position.
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</para>
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</listitem>
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@ -206,8 +202,8 @@ $$ LANGUAGE plpythonu;
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<term>Mapping (dictionary)</term>
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<listitem>
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<para>
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Value for a composite type's column is retrieved from the mapping with
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the column name as key. Example:
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The value for each result type column is retrieved from the mapping
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with the column name as key. Example:
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<programlisting>
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CREATE FUNCTION make_pair (name text, value integer)
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@ -217,8 +213,9 @@ AS $$
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$$ LANGUAGE plpythonu;
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</programlisting>
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Additional dictionary key/value pairs are ignored. Missing keys are
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treated as errors, i.e. to return an SQL null value for any column, insert
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Any extra dictionary key/value pairs are ignored. Missing keys are
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treated as errors.
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To return a SQL null value for any column, insert
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<symbol>None</symbol> with the corresponding column name as the key.
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</para>
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</listitem>
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@ -228,6 +225,7 @@ $$ LANGUAGE plpythonu;
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<term>Object (any object providing method <literal>__getattr__</literal>)</term>
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<listitem>
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<para>
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This works the same as a mapping.
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Example:
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<programlisting>
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@ -261,9 +259,9 @@ $$ LANGUAGE plpythonu;
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<para>
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A <application>PL/Python</application> function can also return sets of
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scalar or composite types. There are serveral ways to achieve this because
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the returned object is internally turned into an iterator. For following
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examples, let's assume to have composite type:
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scalar or composite types. There are several ways to achieve this because
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the returned object is internally turned into an iterator. The following
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examples assume we have composite type:
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<programlisting>
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CREATE TYPE greeting AS (
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@ -272,10 +270,11 @@ CREATE TYPE greeting AS (
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);
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</programlisting>
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Currently known iterable types are:
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A set result can be returned from a:
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<variablelist>
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<varlistentry>
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<term>Sequence types (tuple, list, set)</term>
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<term>Sequence type (tuple, list, set)</term>
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<listitem>
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<para>
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<programlisting>
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@ -341,9 +340,10 @@ $$ LANGUAGE plpythonu;
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<ulink url="http://sourceforge.net/tracker/index.php?func=detail&aid=1483133&group_id=5470&atid=105470">bug #1483133</ulink>,
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some debug versions of Python 2.4
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(configured and compiled with option <literal>--with-pydebug</literal>)
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are known to crash the <productname>PostgreSQL</productname> server.
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are known to crash the <productname>PostgreSQL</productname> server
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when using an iterator to return a set result.
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Unpatched versions of Fedora 4 contain this bug.
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It does not happen in production version of Python or on patched
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It does not happen in production versions of Python or on patched
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versions of Fedora 4.
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</para>
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</warning>
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@ -351,9 +351,6 @@ $$ LANGUAGE plpythonu;
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</listitem>
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</varlistentry>
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</variablelist>
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Whenever new iterable types are added to Python language,
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<application>PL/Python</application> is ready to use it.
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</para>
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<para>
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