Presto 0.100 Documentation

10.23. Release 0.78

10.23. Release 0.78

ARRAY and MAP Types in Hive Connector

The Hive connector now returns arrays and maps instead of json encoded strings, for columns whose underlying type is array or map. Please note that this is a backwards incompatible change, and the JSON函数 will no longer work on these columns, unless you cast() them to the json type.

Session Properties

The Presto session can now contain properties, which can be used by the Presto engine or connectors to customize the query execution. There is a separate namespace for the Presto engine and each catalog. A property for a catalog is simplify prefixed with the catalog name followed by . (dot). A connector can retrieve the properties for the catalog using ConnectorSession.getProperties().

Session properties can be set using the --session command line argument to the Presto CLI. For example:

presto-cli --session color=red --session size=large

For JDBC, the properties can be set by unwrapping the Connection as follows:

connection.unwrap(PrestoConnection.class).setSessionProperty("name", "value");

Note

This feature is a work in progress and will change in a future release. Specifically, we are planning to require preregistration of properties so the user can list available session properties and so the engine can verify property values. Additionally, the Presto grammar will be extended to allow setting properties via a query.

Hive Changes

  • Add storage_format session property to override format used for creating tables.
  • Add write support for VARBINARY, DATE and TIMESTAMP.
  • Add support for partition keys of type TIMESTAMP.
  • Add support for partition keys with null values (__HIVE_DEFAULT_PARTITION__).
  • Fix hive.storage-format option (see Release 0.76).

General Changes

  • Fix expression optimizer, so that it runs in linear time instead of exponential time.
  • Add cardinality() for maps.
  • Fix race condition in SqlTask creation which can cause queries to hang.
  • Fix node-scheduler.multiple-tasks-per-node-enabled option.
  • Fix an exception when planning a query with a UNION under a JOIN.