* fix infinite loop when reading wide table When a wide table is read, the 1st batch would be exceed raw_bytes_threshold, so Scanner should read at least 1 row. Actually, we should adjust batch size automatically to reduce memoery usage.
* fix infinite loop when reading wide table When a wide table is read, the 1st batch would be exceed raw_bytes_threshold, so Scanner should read at least 1 row. Actually, we should adjust batch size automatically to reduce memoery usage.