8.1. Black Hole Connector

The Black Hole connector works like the /dev/null device on Unix-like operating systems for data writing and like /dev/null or /dev/zero for data reading. Metadata for any tables created via this connector is kept in memory on the coordinator and discarded when Presto restarts. Created tables are by default always empty, and any data written to them will be ignored and data reads will return no rows.

Alternatively user upon table creation can specify desired rows number. In such case writes will behave the same as previously - they will be ignored. Reads however will then always return specified number of some constant rows. You shouldn’t relay on the content of such rows.

Warning

This connector will not work properly with multiple coordinators, since each coordinator will have a different metadata.

Configuration

To configure the Black Hole connector, create a catalog properties file etc/catalog/blackhole.properties with the following contents:

connector.name=blackhole

Examples

Create a table using the blackhole connector:

CREATE TABLE blackhole.test.nation AS
SELECT * from tpch.tiny.nation;

Insert data into a table in the blackhole connector:

INSERT INTO blackhole.test.nation
SELECT * FROM tpch.tiny.nation;

Select from the blackhole connector:

SELECT COUNT(*) FROM blackhole.test.nation;

The above query will always return 0.

Create a table with constant number of rows:

CREATE TABLE blackhole.test.nation WITH
    (splits_count = 500,
     pages_per_split = 1000,
     rows_per_page = 2000)
AS SELECT * from tpch.tiny.nation;
SELECT COUNT(*) FROM blackhole.test.nation;

The above query will return value 1 000 000 000 (500 * 1000 * 2000).

Presto 0.115t Documentation