# Presto 316 Documentation

## 12.19. Release 0.214

## General Changes

- Fix history leak in coordinator for failed or canceled queries.
- Fix memory leak related to query tracking in coordinator that was introduced in Release 0.213.
- Fix planning failures when lambdas are used in join filter expression.
- Fix responses to client for certain types of errors that are encountered during query creation.
- Improve error message when an invalid comparator is provided to the `array_sort()` function.
- Improve performance of lookup operations on map data types.
- Improve planning and query performance for queries with `TINYINT`, `SMALLINT` and `VARBINARY` literals.
- Fix issue where queries containing distributed `ORDER BY` and aggregation could sometimes fail to make progress when data was spilled.
- Make top N row number optimization work in some cases when columns are pruned.
- Add session property `optimize-top-n-row-number` and configuration property `optimizer.optimize-top-n-row-number` to toggle the top N row number optimization.
- Add `ngrams()` function to generate N-grams from an array.
- Add qdigest type and associated Quantile Digest Functions.
- Add functionality to delay query execution until a minimum number of workers nodes are available. The minimum number of workers can be set with the `query-manager.required-workers` configuration property, and the max wait time with the `query-manager.required-workers-max-wait` configuration property.
- Remove experimental pre-allocated memory system, and the related configuration property `experimental.preallocate-memory-threshold`.

## Security Changes

- Add functionality to refresh the configuration of file-based access controllers. The refresh interval can be set using the `security.refresh-period` configuration property.

## JDBC Driver Changes

- Clear update count after calling `Statement.getMoreResults()`.

## Web UI Changes

- Show query warnings on the query detail page.
- Allow selecting non-default sort orders in query list view.

## Hive Connector Changes

- Prevent ORC writer from writing stripes larger than the maximum configured size.
- Add `hive.s3.upload-acl-type` configuration property to specify the type of ACL to use while uploading files to S3.
- Add Hive metastore API recording tool for remote debugging purposes.
- Add support for retrying on metastore connection errors.

## Verifier Changes

- Handle SQL execution timeouts while rewriting queries.