my ho <[EMAIL PROTECTED]> writes:
> If anyone can help pls, I have a question abt the
> execution of cursor create/fetch/move , in particular
> about disk cost. When a cursor is created, is the
> whole table (with the required columns) got put into
> memory?

No.  The plan is set up and then incrementally executed each time you
say FETCH.

> how does postgre speed up the query in
> compare to normal selection?

The only difference from a SELECT is that the planner will prefer
"fast-start" plans, on the theory that you may not be intending
to retrieve the whole result.  For instance it might prefer an
indexscan to a seqscan + sort, when it otherwise wouldn't.

                        regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
      joining column's datatypes do not match

Reply via email to