Github user dyozie commented on a diff in the pull request:
    --- Diff: plext/ ---
    @@ -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;
    +gpadmin=# select count_orders();
    + my_count 
    +   830513
    +(1 row)
    +For additional information on creating SQL functions, refer to [Query 
Language (SQL) 
Functions]( 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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