Memory Connector#

The Memory connector stores all data and metadata in RAM on workers and both are discarded when Presto restarts.

Configuration#

To configure the Memory connector, create a catalog properties file etc/catalog/memory.properties with the following contents:

connector.name=memory
memory.max-data-per-node=128MB

memory.max-data-per-node defines memory limit for pages stored in this connector per each node (default value is 128MB).

Examples#

Create a table using the Memory connector:

CREATE TABLE memory.default.nation AS
SELECT * from tpch.tiny.nation;

Insert data into a table in the Memory connector:

INSERT INTO memory.default.nation
SELECT * FROM tpch.tiny.nation;

Select from the Memory connector:

SELECT * FROM memory.default.nation;

Drop table:

DROP TABLE memory.default.nation;

Limitations#

  • After DROP TABLE memory is not released immediately. It is released after the next write access to memory connector.

  • When one worker fails/restarts, all data that was stored in its memory is lost. To prevent silent data loss the connector throws an error on any read access to such corrupted table.

  • When a query fails for any reason during writing to memory table, the table enters an undefined state. The table should be dropped and recreated manually. Reading attempts from the table may fail, or may return partial data.

  • When the coordinator fails/restarts, all metadata about tables is lost. The tables remain on the workers, but become inaccessible.

  • This connector does not work properly with multiple coordinators, since each coordinator has different metadata.