Re: Lowering the ever-growing heap->pd_lower - Mailing list pgsql-hackers

Hi,

On 2022-04-08 15:04:37 -0400, Robert Haas wrote:
> I meant wasting space in the page. I think that's a real concern.
> Imagine you allowed 1000 line pointers per page. Each one consumes 2
> bytes.

It's 4 bytes per line pointer, right?

struct ItemIdData {
        unsigned int               lp_off:15;            /*     0: 0  4 */
        unsigned int               lp_flags:2;           /*     0:15  4 */
        unsigned int               lp_len:15;            /*     0:17  4 */

        /* size: 4, cachelines: 1, members: 3 */
        /* last cacheline: 4 bytes */
};

Or am I confusing myself somehow?


I do wish the length of the tuple weren't in ItemIdData, but part of the
tuple, so we'd not waste this space for dead items (I think it'd also simplify
more code than it'd complicate). But ...

- Andres