Presto 0.244 Documentation

4.8. Function Namespace Managers

4.8. Function Namespace Managers

Warning

This is an experimental feature being actively developed. The way Function Namespace Managers are configured might be changed.

Function namespace managers support storing and retrieving SQL functions, allowing the Presto engine to perform actions such as creating, 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 storing functions. However, it is not a full fledged schema as it does not support storing tables and views, but only functions.

Each Presto function, whether built-in or user-defined, resides in a function namespace. All built-in functions reside in the presto.default function namespace. The qualified function name of a function is the function namespace in which it reside followed by its function name (e.g. example.test.func). Built-in functions can be referenced in queries with their function namespaces omitted, while user-defined functions needs to be referenced by its qualified function name. A function is uniquely identified by its qualified function name and parameter type list.

Each function namespace manager binds to a catalog name and manages all functions within that catalog. Using the catalog name of an existing connector 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 they support 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 related information in MySQL.

To instantiate a MySQL-based function namespace manager that manages catalog example, administrator needs to first have a running MySQL server. Suppose the MySQL server can be reached at localhost:1080, add a file etc/function-namespace/example.properties with the following 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 namespace manager configuration, two MySQL tables will be created if they do not exist.

  • example_function_namespaces stores function namespaces of the catalog example.
  • example_sql_functions stores SQL-invoked functions of the catalog example.

Multiple function namespace managers can be instantiated by placing multiple properties files under etc/function-namespace. They may be configured to use the same tables. If so, each manager will only create and interact with entries of the catalog to which it binds.

To create a new function namespace, insert into the example_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.