Re: Bitmapset data type???

On Sun, Dec 19, 2004 at 05:39:43PM +0200, Martha Chronopoulou wrote:

Hi,

> "A bitmap set can represent any set of nonnegative integers, although it
> is mainly intented for sets where the maximum value is not large, say
> at most a few hundred."

Clearly this can only come from the contorted mind of a JPEG hacker.
(And indeed it does, as you can see from the CVS logs.)

> I'm tring to understand a part of code of postgres and I saw a line like
> this:
> "bms_is_subset(restrictinfo->right_relids,outerrelids)" (createplan.c,
> function get_switched_clauses() at ~/src/backend/optimizer/plan).

What that is doing is check whether restrictingo->right_relids is a
subset of outerrelids.

> I don't understand the data types of the the arguments
> of that function.

The only thing you need to know is that it represents a set of integers.
Anything beyond that is going to drive you crazy (and is irrelevant
anyway.)

--
Alvaro Herrera (<alvherre[(at)]dcc(dot)uchile(dot)cl>)
"I can't go to a restaurant and order food because I keep looking at the
fonts on the menu. Five minutes later I realize that it's also talking
about food" (Donald Knuth)