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https://issues.apache.org/jira/browse/HAWQ-1096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15587170#comment-15587170
]
ASF GitHub Bot commented on HAWQ-1096:
--------------------------------------
Github user dyozie commented on a diff in the pull request:
https://github.com/apache/incubator-hawq-docs/pull/25#discussion_r83978854
--- Diff: plext/builtin_langs.html.md.erb ---
@@ -0,0 +1,110 @@
+---
+title: Using HAWQ Built-In Languages
+---
+
+This section provides an introduction to using the HAWQ built-in languages.
+
+HAWQ supports user-defined functions created with the SQL and C built-in
languages. HAWQ also supports user-defined aliases for internal functions.
+
+
+## <a id="enablebuiltin"></a>Enabling Built-in Language Support
+
+Support for SQL, internal, and C language user-defined functions is
enabled by default for all HAWQ databases.
+
+## <a id="builtinsql"></a>SQL
+
+SQL functions execute an arbitrary list of SQL statements. The SQL
statements in the body of an SQL function must be separated by semicolons. The
final statement in a non-void-returning SQL function must be a
[SELECT](../reference/sql/SELECT.html) that returns data of the type specified
by the function's return type. The function will return a single or set of rows
corresponding to this last SQL query.
+
+The following example creates and calls an SQL function to count the
number of rows of the database named `orders`:
+
+``` sql
+gpadmin=# CREATE FUNCTION count_orders() RETURNS bigint AS $$
+ SELECT count(*) FROM orders;
+$$ LANGUAGE SQL;
+CREATE FUNCTION
+gpadmin=# select count_orders();
+ my_count
+----------
+ 830513
+(1 row)
+```
+
+For additional information on creating SQL functions, refer to [Query
Language (SQL)
Functions](https://www.postgresql.org/docs/8.2/static/xfunc-sql.html) in the
PostgreSQL documentation.
+
+## <a id="builtininternal"></a>Internal
+
+Many HAWQ internal functions are written in C. These functions are
declared during initialization of the database cluster and statically linked to
the HAWQ server. See [Built-in Functions and
Operators](../query/functions-operators.html#topic29) for detailed information
on HAWQ internal functions.
+
+While users cannot define new internal functions, they can create aliases
for existing internal functions.
+
+The following example creates a new function named `all_caps` that will be
defined as an alias for the `upper` HAWQ internal function:
+
+
+``` sql
+gpadmin=# CREATE FUNCTION all_caps (text) RETURNS text AS 'upper'
+ LANGUAGE internal STRICT;
+CREATE FUNCTION
+gpadmin=# SELECT all_caps('change me');
+ all_caps
+-----------
+ CHANGE ME
+(1 row)
+
+```
+
+For more information on aliasing internal functions, refer to [Internal
Functions](https://www.postgresql.org/docs/8.2/static/xfunc-internal.html) in
the PostgreSQL documentation.
+
+## <a id="builtininternal"></a>C
+
+User-defined functions written in C must be compiled into shared libraries
to be loaded by the HAWQ server on demand. This dynamic loading distinguishes C
language functions from internal functions that are written in C.
--- End diff --
Avoid passive voice here: "You must compile user-defined functions written
in C into shared libraries so that the HAWQ server can load them on demand."
> document the HAWQ built-in languages (SQL, C, internal)
> -------------------------------------------------------
>
> Key: HAWQ-1096
> URL: https://issues.apache.org/jira/browse/HAWQ-1096
> Project: Apache HAWQ
> Issue Type: Improvement
> Components: Documentation
> Reporter: Lisa Owen
> Assignee: David Yozie
> Priority: Minor
>
> the HAWQ docs do not discuss the built-in languages supported by HAWQ - SQL,
> C and internal. add content to introduce these languages with relevant
> examples and links.
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