This is the
buf will contain a copy of the row to be
deleted. The server will call this right after the current row
has been called (from either a previous
rnd_next() or index call). If you keep a
pointer to the last row or can access a primary key it will
make doing the deletion quite a bit easier. Keep in mind that
the server does not guarantee consecutive deletions.
ORDER BY clauses can be used.
sql_udf.cc to manage internal table
information. Called in
sql_select it is used for removing
duplicates, while in
insert it is used for