To determine which Hive functions and operators are available, you reload functions,
and then use the SHOW FUNCTIONS statement. An optional pattern in the statement filters the
list of functions returned by the statement.
In this task, you first reload functions to make available any user-defined
functions that were registered in Hive session after your session started. The
syntax is:
RELOAD (FUNCTION|FUNCTIONS);
Next, you use the
SHOW FUNCTIONS statement. The syntax of this statement is:
SHOW FUNCTIONS [LIKE "<pattern>"];
<pattern> represents
search characters that can include regular expression wildcards. Finally, you get
more information about use by issuing the DESCRIBE FUNCTION statement.
-
Open the Hive shell.
Open a client connection, for example:
beeline -u jdbc:hive2://mycloudhost-3.com:10000 -n <your user name> -p
-
Reload functions to ensure all registered UDFs are available in your
session.
Use the plural form of the command. RELOAD FUNCTION is for backward compatibility.
-
Generate a list of available built-in and user-defined functions (UDFs).
The list of built-in functions, operators, and UDFs appear.
+------------------------------+
| tab_name |
+------------------------------+
| ! |
| != |
| $sum0 |
| % |
...
-
Generate a filtered list of functions using the regular expression wildcard
%
.
SHOW FUNCTIONS LIKE "a%";
All available functions that begin with the character
a
appear.
+------------------------------+
| tab_name |
+------------------------------+
| abs |
| acos |
| add_months |
...
-
Get more information about a particular function.
+-------------------------------------------+
| tab_name |
+-------------------------------------------+
| ABS(x) - returns the absolute value of x |
+-------------------------------------------+
-
Get more information about the function.
DESCRIBE FUNCTION EXTENDED abs;
+----------------------------------------------------+
| tab_name |
+----------------------------------------------------+
| ABS(x) - returns the absolute value of x |
| Synonyms: abs |
| Example: |
| > SELECT ABS(0) FROM src LIMIT 1; |
| 0 |
| > SELECT ABS(-5) FROM src LIMIT 1; |
| 5 |
| Function class:org.apache.hadoop.hive.ql.udf.generic.GenericUDFAbs |
| Function type:BUILTIN |
+----------------------------------------------------+