# Presto 316 Documentation

## 12.65. Release 0.168

## General Changes

- Fix correctness issues for certain `JOIN` queries that require implicit coercions for terms in the join criteria.
- Fix invalid “No more locations already set” error.
- Fix invalid “No more buffers already set” error.
- Temporarily revert empty join short-circuit optimization due to issue with hanging queries.
- Improve performance of `DECIMAL` type and operators.
- Optimize window frame computation for empty frames.
- `json_extract()` and `json_extract_scalar()` now support escaping double quotes or backslashes using a backslash with a JSON path subscript. This changes the semantics of any invocation using a backslash, as backslashes were previously treated as normal characters.
- Improve performance of `filter()` and `map_filter()` lambda functions.
- Add Memory Connector.
- Add `arrays_overlap()` and `array_except()` functions.
- Allow concatenating more than two arrays with `concat()` or maps with `map_concat()`.
- Add a time limit for the iterative optimizer. It can be adjusted via the `iterative_optimizer_timeout` session property or `experimental.iterative-optimizer-timeout` configuration option.
- `ROW` types are now orderable if all of the field types are orderable. This allows using them in comparison expressions, `ORDER BY` and functions that require orderable types (e.g., `max()`).

## JDBC Driver Changes

- Update `DatabaseMetaData` to reflect features that are now supported.
- Update advertised JDBC version to 4.2, which part of Java 8.
- Return correct driver and server versions rather than `1.0`.

## Hive Changes

- Fix reading decimals for RCFile text format using non-optimized reader.
- Fix bug which prevented the file based metastore from being used.
- Enable optimized RCFile reader by default.
- Common user errors are now correctly categorized.
- Add new, experimental, RCFile writer optimized for Presto. The new writer can be enabled with the `rcfile_optimized_writer_enabled` session property or the `hive.rcfile-optimized-writer.enabled` Hive catalog property.

## Cassandra Changes

- Add predicate pushdown for clustering key.

## MongoDB Changes

- Allow SSL connections using the `mongodb.ssl.enabled` config flag.

## SPI Changes

- ConnectorIndex now returns `ConnectorPageSource` instead of `RecordSet`. Existing connectors that support index join can use the `RecordPageSource` to adapt to the new API.