Github user dyozie commented on a diff in the pull request: https://github.com/apache/incubator-hawq-docs/pull/25#discussion_r83978549 --- 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: --- End diff -- Edit: change "that will be defined as an" to "that is an"
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