Dear Postgresql experts,
According to the documentation for MOVE, it returns the number of rows that it has moved over. It seems to me that this is true for MOVE FORWARD n, but not for MOVE RELATIVE n or MOVE ABSOLUTE n when it always returns 1:
db=> declare c scroll cursor for select * from p; DECLARE CURSOR db=> move absolute -1 in c; MOVE 1 db=> move absolute 1 in c; MOVE 1 db=> move absolute 10 in c; MOVE 1 db=> move relative 10 in c; MOVE 1 db=> move relative 100 in c; MOVE 1 db=> move forward 100 in c; MOVE 100
Is this a bug?
What I'm actually trying to do is to find the number of rows in the query result. I was hoping to be able to do a "MOVE ABSOLUTE -1" to get this. Any other suggestions?
Taking a step further back, here's the real problem: I want to present the user with an index page to chunks of a table, e.g.
Aardvark - Frog Frozen - Rabbit Rabies - Zoo
So I need to get something like rows 1, n/3-1, n/3, 2n/3-1, 2n/3, n. Efficiency is of concern. Is there some way of asking "WHERE row_number MOD x < 2"? Currently I am running a count(*) version of the query to get the number of rows and then running it again with a cursor and fetching the necessary rows. Any other ideas?
This is with 7.4.2.
Regards,
--Phil.
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