Github user lisakowen commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/77#discussion_r94606714
--- Diff: plext/using_plpython.html.md.erb ---
@@ -2,374 +2,608 @@
title: Using PL/Python in HAWQ
---
-This section contains an overview of the HAWQ PL/Python language extension.
+This section provides an overview of the HAWQ PL/Python procedural
language extension.
## <a id="abouthawqplpython"></a>About HAWQ PL/Python
-PL/Python is a loadable procedural language. With the HAWQ PL/Python
extension, you can write HAWQ user-defined functions in Python that take
advantage of Python features and modules to quickly build robust database
applications.
+PL/Python is embedded in your HAWQ product distribution or within your
HAWQ build if you chose to enable it as a build option.
+
+With the HAWQ PL/Python extension, you can write user-defined functions in
Python that take advantage of Python features and modules, enabling you to
quickly build robust HAWQ database applications.
HAWQ uses the system Python installation.
### <a id="hawqlimitations"></a>HAWQ PL/Python Limitations
-- HAWQ does not support PL/Python triggers.
+- HAWQ does not support PL/Python trigger functions.
- PL/Python is available only as a HAWQ untrusted language.
## <a id="enableplpython"></a>Enabling and Removing PL/Python Support
-To use PL/Python in HAWQ, you must either use a pre-compiled version of
HAWQ that includes PL/Python or specify PL/Python as a build option when
compiling HAWQ.
+To use PL/Python in HAWQ, you must either install a binary version of HAWQ
that includes PL/Python or specify PL/Python as a build option when compiling
HAWQ from source.
+
+PL/Python user-defined functions (UDFs) are registered at the database
level. To create and run a PL/Python UDF on a database, you must register the
PL/Python language with the database.
+
+On every database to which you want to install and enable PL/Python:
+
+1. Connect to the database using the `psql` client:
+
+ ``` shell
+ $ psql -d <dbname>
+ ```
+
+ Replace \<dbname\> with the name of the target database.
+
+2. Run the following SQL command to register the PL/Python procedural
language; you must be a database superuser to register new languages:
+
+ ``` sql
+ dbname=# CREATE LANGUAGE plpythonu;
+ ```
-To create and run a PL/Python user-defined function (UDF) in a database,
you must register the PL/Python language with the database. On every database
where you want to install and enable PL/Python, connect to the database using
the `psql` client.
+ **Note**: `plpythonu` is installed as an *untrusted* language; it
offers no way of restricting what you can program in UDFs created with the
language.
--- End diff --
yes, it is kind of confusing. the operations one can perform with trusted
languages are restricted; unprivileged database users can be permitted to
create and run UDFs created in these languages. untrusted languages are the
opposite - you can do pretty much anything, and i think are restricted to
superusers. (will verify.)
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