# Presto 316 Documentation

## 12.49. Release 0.184

## General Changes

- Fix query execution failure for `split_to_map(...)[...]`.
- Fix issue that caused queries containing `CROSS JOIN` to continue using CPU resources even after they were killed.
- Fix planning failure for some query shapes containing `count(*)` and a non-empty `GROUP BY` clause.
- Fix communication failures caused by lock contention in the local scheduler.
- Improve performance of `element_at()` for maps to be constant time rather than proportional to the size of the map.
- Improve performance of queries with gathering exchanges.
- Require `coalesce()` to have at least two arguments, as mandated by the SQL standard.
- Add `hamming_distance()` function.

## JDBC Driver Changes

- Always invoke the progress callback with the final stats at query completion.

## Web UI Changes

- Add worker status page with information about currently running threads and resource utilization (CPU, heap, memory pools). This page is accessible by clicking a hostname on a query task list.

## Hive Changes

- Fix partition filtering for keys of `CHAR`, `DECIMAL`, or `DATE` type.
- Reduce system memory usage when reading table columns containing string values from ORC or DWRF files. This can prevent high GC overhead or out-of-memory crashes.

## TPCDS Changes

- Fix display of table statistics when running `SHOW STATS FOR ...`.

## SPI Changes

- Row columns or values represented with `ArrayBlock` and `InterleavedBlock` are no longer supported. They must be represented as `RowBlock` or `SingleRowBlock`.
- Add `source` field to `ConnectorSession`.