Bug Fixes
* Fix a bug in QueryEngine::IsValidPartitionedDML where it failed to parse PostgreSQL parameter placeholders
* Support setting or dropping NOT NULL in PostgreSQL.
* Allow updating tables with indexes storing pending commit timestamps.
* Fix emulator feature flags returning references after losing lock in issue 370.
* Fix nullptr issue in Change Stream schema changes in issue 371.
New Feature
* DDL support for cloud queue
* Support creating tables without user-defined primary keys.
* Add support for TABLESAMPLE to the PostgreSQL dialect.
* Increase max tables per database to 5000 and max indexes per database to 10000.
* Support `IS DISTINCT FROM` / `IS NOT DISTINCT FROM` expressions in Spanner Emulator.