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From dyozie <...@git.apache.org>
Subject [GitHub] incubator-hawq-docs pull request #25: HAWQ-1096 - add content for hawq built...
Date Wed, 19 Oct 2016 00:31:45 GMT
Github user dyozie commented on a diff in the pull request:

    --- 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;
    +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.
    --- End diff --
    Reword:  **You** cannot define new internal functions, **but you** can create...

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