On Wed, Nov 13, 2019 at 10:04:36AM -0800, Mark Dilger wrote:
On 11/13/19 7:28 AM, Tomas Vondra wrote:
Hi,
here's an updated patch, with some minor tweaks based on the review and
added tests (I ended up reworking those a bit, to make them more like
the existing ones).
Thanks, Tomas, for the new patch set!
Attached are my review comments so far, in the form of a patch applied
on top of yours.
Thanks.
1) It's not clear to me why adding 'const' to the List parameters would
be useful? Can you explain?
2) I think you're right we can change find_strongest_dependency to do
/* also skip weaker dependencies when attribute count matches */
if (strongest->nattributes == dependency->nattributes &&
strongest->degree >= dependency->degree)
continue;
That'll skip some additional dependencies, which seems OK.
3) It's not clear to me what you mean by
* TODO: Improve this code comment. Specifically, why would we
* ignore that no rows will match? It seems that such a discovery
* would allow us to return an estimate of 0 rows, and that would
* be useful.
added to dependencies_clauselist_selectivity. Are you saying we
should also compute selectivity estimates for individual clauses and
use Min() as a limit? Maybe, but that seems unrelated to the patch.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
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