char* getColPointer ( int i, int _slice_num, int j = 0 ) const
get buffer pointer.
when getColPointer(2,4,1), it means the 2nd column was divied into 4 sections, return the pointer of the 2nd section
Parameters:
| i | column id |
| _slice_num | divide column i into _slice_num parts |
| j | get the j’th part pointer after dividing |
Returns:
column buffer pointer