12.177. Release 0.70

Warning

This release contained a packaging error that resulted in anunusable server tarball. Do not use this release.

Views

We have added support for creating views within Presto.Views are defined using Presto syntax but are stored (as blobs)by connectors. Currently, views are supported by theRaptor and Hive connectors. For the Hive connector, views arestored within the Hive metastore as Hive views, but they cannotbe queried by Hive, nor can Hive views be queried by Presto.

See CREATE VIEW and DROP VIEWfor details and examples.

DUAL Table

The synthetic DUAL table is no longer supported. As an alternative, pleasewrite your queries without a FROM clause or use the VALUES syntax.

Presto Verifier

There is a new project, Presto Verifier, which can be used toverify a set of queries against two different clusters.

Connector Improvements

  • Connectors can now add hidden columns to a table. Hidden columns are notdisplayed in DESCRIBE or information_schema, and are notconsidered for SELECT *. As an example, we have added a hiddenrow_number column to the tpch connector.
  • Presto contains an extensive test suite to verify the correctness. This testsuite has been extracted into the presto-test module for use duringconnector development. For an example, see TestRaptorDistributedQueries.

Machine Learning Functions

We have added two new machine learning functions, which can be usedby advanced users familiar with LIBSVM. The functions arelearn_libsvm_classifier and learn_libsvm_regressor. Both take aparameters string which has the form key=value,key=value

General Changes

  • New comparison functions: greatest() and least()
  • New window functions: first_value(), last_value(), and nth_value()
  • We have added a config option to disable falling back to the interpreter whenexpressions fail to be compiled to bytecode. To set this option, add compiler.interpreter-enabled=false to etc/config.properties.This will force certain queries to fail rather than running slowly.
  • DATE values are now implicitly coerced to TIMESTAMP and TIMESTAMP WITH TIME ZONEby setting the hour/minute/seconds to 0 with respect to the session timezone.
  • Minor performance optimization when planning queries over tables with tens ofthousands of partitions or more.
  • Fixed a bug when planning ORDER BY … LIMIT queries which could result induplicate and un-ordered results under rare conditions.
  • Reduce the size of stats collected from tasks, which dramatically reducesgarbage generation and improves coordinator stability.
  • Fix compiler cache for expressions.
  • Fix processing of empty or commented out statements in the CLI.

Hive Changes

  • There are two new configuration options for the Hive connector,hive.max-initial-split-size, which configures the size of theinitial splits, and hive.max-initial-splits, which configuresthe number of initial splits. This can be useful for speeding up smallqueries, which would otherwise have low parallelism.
  • The Hive connector will now consider all tables with a non-empty valuefor the table property presto_offline to be offline. The value of theproperty will be used in the error message.
  • We have added support for for DROP TABLE in the hive connector.By default, this feature is not enabled. To enable it, sethive.allow-drop-table=true in your Hive catalog properties file.
  • Ignore subdirectories when generating splits(this now matches the non-recursive behavior of Hive).
  • Fix handling of maps with null keys.