Github user dyozie commented on a diff in the pull request: https://github.com/apache/incubator-hawq-docs/pull/25#discussion_r83978153 --- 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 --- End diff -- This id value is the same as the previous one - should be unique. Also change header to "C Functions"?
--- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. ---