Scalable updates on distribution columns of tables with indices

In former versions, updates on distribution columns triggered an all-index rebuild of the table. Even single row updates could become quite expensive.

Improvement
Updates on distribution columns are handled by copying (delete marking) and redistributing of updated rows. Indices are updated through index inserts.

Large amounts of updated rows still trigger index rebuilds as this is faster than large updates on indices. Delete marking of update rows may trigger a delete reorganization with index rebuilds when table delete margin is reached (25% deleted marked rows).