On 3/28/23 10:28, Dominique Devienne wrote:
On Tue, Mar 28, 2023 at 6:06 PM Ron <ronljohnso...@gmail.com> wrote:
You can only get from parent to grandchild via//child.id
<http://child.id> to grandchild.parent, so why not cluster
grandchild on grandchild.parent?
Hi. I don't understand your question. Yes, of course, if I want all
grand-children of a given parent, I'll do for example:
select p.id <http://p.id>, c.id <http://c.id>, c.name <http://c.name>,
gc.*
from grandchild gc
join child c on gc.parent = c.id <http://c.id>
join parent p on c.parent = p.id <http://p.id>
where p.name <http://p.name> = $1
But w/o clustering on a denormalized grandchild.grandparent FK column,
as Peter showed,
and cluster only on grandchild.parent, that's not going to access a
mostly continuous range
of pages to fetch those all grandchild rows for that one parent. But
probably 10 to 50 "row-clusters",
given the fan-out I mentioned earlier at the child-table level. Or am
I missing something?
Are you using HDD (spinning) or SSD discs?
Is you world strictly three levels: grand,parent,child?
What tests have you done so far to compare clustered to non-clustered?
