Add docs.

Signed-off-by: Yury-Fridlyand <[email protected]>

docs/user/dql/functions.rst

@@ -3004,3 +3004,27 @@ Example searching for field Tags::
     | [Winnie-the-<em>Pooh</em>]                   |
     +----------------------------------------------+
 
+System Functions
+================
+
+TYPEOF
+------
+
+Description
+>>>>>>>>>>>
+
+Usage: typeof(expr) function returns name of the data type of the value that is passed to it. This can be helpful for troubleshooting or dynamically constructing SQL queries.
+
+Argument type: ANY
+
+Return type: STRING
+
+Example::
+
+    os> select typeof(DATE('2008-04-14')) as `typeof(date)`, typeof(1) as `typeof(int)`, typeof(now()) as `typeof(now())`, typeof(accounts) as `typeof(column)` from people
+    fetched rows / total rows = 1/1
+    +----------------+---------------+-----------------+------------------+
+    | typeof(date)   | typeof(int)   | typeof(now())   | typeof(column)   |
+    |----------------+---------------+-----------------+------------------|
+    | DATE           | INTEGER       | DATETIME        | STRUCT           |
+    +----------------+---------------+-----------------+------------------+

docs/user/ppl/functions/system.rst

@@ -0,0 +1,31 @@
+================
+System Functions
+================
+
+.. rubric:: Table of contents
+
+.. contents::
+   :local:
+   :depth: 1
+
+TYPEOF
+------
+
+Description
+>>>>>>>>>>>
+
+Usage: typeof(expr) function returns name of the data type of the value that is passed to it. This can be helpful for troubleshooting or dynamically constructing SQL queries.
+
+Argument type: ANY
+
+Return type: STRING
+
+Example::
+
+    os> source=people | eval `typeof(date)` = typeof(DATE('2008-04-14')), `typeof(int)` = typeof(1), `typeof(now())` = typeof(now()), `typeof(column)` = typeof(accounts) | fields `typeof(date)`, `typeof(int)`, `typeof(now())`, `typeof(column)`
+    fetched rows / total rows = 1/1
+    +----------------+---------------+-----------------+------------------+
+    | typeof(date)   | typeof(int)   | typeof(now())   | typeof(column)   |
+    |----------------+---------------+-----------------+------------------|
+    | DATE           | INTEGER       | DATETIME        | STRUCT           |
+    +----------------+---------------+-----------------+------------------+

docs/user/ppl/index.rst

@@ -84,6 +84,8 @@ The query start with search command and then flowing a set of command delimited
 
   - `Type Conversion Functions <functions/conversion.rst>`_
 
+  - `System Functions <functions/system.rst>`_
+
 * **Optimization**
 
   - `Optimization <../../user/optimization/optimization.rst>`_