handler::read_multi_range_XXX and HA_NEED_READ_RANGE_BUFFER

[Zardosht Kasheff]

Hello all,

In MySQL 5.1, I see that NDB exposes the HA_NEED_READ_RANGE_BUFFER
flag as a table flag, and the result is that the functions
handler::read_multi_range_first and handler::read_multi_range_next may
possibly use the buffer passed in somehow.

What is the contract here? How may the variable multi_range_buffer be
used if a handler exposes HA_NEED_READ_RANGE_BUFFER?

Thanks
-Zardosht