Server mode: concurrently using the same connection could throw an exception Connection is broken: unexpected status

Server mode: concurrently using the same connection could throw an exception Connection is broken: unexpected status

Multi-threaded processing: concurrent deleting the same row could throw the exception Row not found when trying to delete

MVStore transactions: a thread could see a change of a different thread within a different map. Pull request #153.

MVStore transactions: a thread could see a change of a different thread within a different map. Pull request #153.

Test case for undoLog synchronization race and proposed fix

COLUMNS metatable

Table engine improvements