1. Btree: use TID as (last) part of index key; prepare btree for low-level locking (it's now possible to lose root page). 2. Vacuum: speed up index cleaning; release pg_class lock after updation statistic for a table. 3. Buffer manager: error handling broken; should flush only buffers changed by backend itself. 4. Implement shared catalog cache; get rid of invalidation code. 5. Subselects: in target list; in FROM. 6. Transaction manager: get rid of pg_variable; do not prefetch XIDs; nested transactions; savepoints.