This is the
Used for finding row previously marked with position. This is useful for large sorts.
This is like rnd_next, but you are given a position to use to determine the row. The position will be of the type that you stored in ref. You can use ha_get_ptr(pos,ref_length) to retrieve whatever key or position you saved when position() was called. Called from filesort.cc records.cc sql_insert.cc sql_select.cc sql_update.cc.