Announcing Vitess 19

Vitess 19 introduces performance improvements such as a new connection pool for Tablets, faster hashing in sharded Vitess clusters, and faster comparisons in cross-shard aggregations. Query compatibility is enhanced with support for multi-table delete operations and non-recursive CTEs. Online DDL now includes backoff for cut-over attempts and forced cut-over. Support for MySQL 5.7 is being dropped, and tablet throttlers now communicate exclusively via gRPC. The release also deprecates several VTTablet flags and changes the EXPLAIN statement format. ExecuteFetchAsDBA now rejects multi-statement SQL.