5.12. Memory Connector

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

Configuration

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

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

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

Examples

Create a table using the Memory connector:

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

Insert data into a table in the Memory connector:

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

Select from the Memory connector:

  1. SELECT * FROM memory.default.nation;

Drop table:

  1. DROP TABLE memory.default.nation;

Memory Connector Limitations

  • After DROP TABLE memory is not released immediately. It isreleased after next write access to memory connector.
  • When one worker fails/restarts all data that were stored in itsmemory will be lost forever. To prevent silent data loss thisconnector will throw an error on any read access to suchcorrupted table.
  • When query fails for any reason during writing to memory table,table will be in undefined state. Such table should be droppedand recreated manually. Reading attempt from such table may failor may return partial data.
  • When coordinator fails/restarts all metadata about tables willbe lost, but tables’ data will be still present on the workershowever they will be inaccessible.
  • This connector will not work properly with multiplecoordinators, since each coordinator will have a differentmetadata.