4.7. Function Namespace Managers
Warning
This is an experimental feature being actively developed. The wayFunction Namespace Managers are configured might be changed.
Function namespace managers support storing and retrieving SQLfunctions, allowing the Presto engine to perform actions such ascreating, altering, deleting functions.
A function namespace is in the format of catalog.schema
(e.g.example.test
). It can be thought of as a schema for storingfunctions. However, it is not a full fledged schema as it does notsupport storing tables and views, but only functions.
Each Presto function, whether built-in or user-defined, resides ina function namespace. All built-in functions reside in thepresto.default
function namespace. The qualified function name ofa function is the function namespace in which it reside followed byits function name (e.g. example.test.func
). Built-in functions canbe referenced in queries with their function namespaces omitted, whileuser-defined functions needs to be referenced by its qualified functionname. A function is uniquely identified by its qualified function nameand parameter type list.
Each function namespace manager binds to a catalog name and manages allfunctions within that catalog. Using the catalog name of an existingconnector is discouraged, as the behavior is not defined nor tested,and will be disallowed in the future.
Currently, those catalog names do not correspond to real catalogs.They cannot be specified as the catalog in a session, nor do theysupport CREATE SCHEMA, ALTER SCHEMA,DROP SCHEMA, or SHOW SCHEMAS. Instead,namespaces can be added using the methods described below.
Configuration
Presto currently stores all function namespace manager relatedinformation in MySQL.
To instantiate a MySQL-based function namespace manager that managescatalog example
, administrator needs to first have a running MySQLserver. Suppose the MySQL server can be reached at localhost:1080
,add a file etc/function-namespace/example.properties
with thefollowing contents:
- function-namespace-manager.name=mysql
- database-url=localhost:1080
- function-namespaces-table-name=example_function_namespaces
- functions-table-name=example_sql_functions
When Presto first starts with the above MySQL function namespacemanager configuration, two MySQL tables will be created if they donot exist.
example_function_namespaces
stores function namespaces ofthe catalogexample
.example_sql_functions
stores SQL-invoked functions of thecatalogexample
.
etc/function-namespace
. Theymay be configured to use the same tables. If so, each manager willonly create and interact with entries of the catalog to which it binds.
To create a new function namespace, insert into theexample_function_namespaces
table:
- INSERT INTO example_function_namespaces (catalog_name, schema_name)
- VALUES('example', 'test');
Configuration Reference
function-namespace-manager.name
is the type of the function namespace manager to instantiate. Currently, only mysql
is supported.
The following table lists all configuration properties supported by the MySQL function namespace manager.
Name | Description |
---|---|
database-url | The URL of the MySQL database used by the MySQL function namespace manager. |
function-namespaces-table-name | The name of the table that stores all the function namespaces managed by this manager. |
functions-table-name | The name of the table that stores all the functions managed by this manager. |