MaxUnCommitedLogSize is the max size of uncommitted log, the unit is Byte.

Set if the key has been deleted.

Set if the value is NOT stored directly next to key.

4 * KB.

given all tables in range partition, if eID is not 0, caller can call stream.Truncate(eID) totruncate the stream, in our system, every extentID is bigger than 0.RETURN: if tables is nil, do not compactif table's estimated size is near maxCapacity, minor compaction policy will not choose this table.