| From: | Andy Fan <zhihuifan1213(at)163(dot)com> |
|---|---|
| To: | Andrei Lepikhov <a(dot)lepikhov(at)postgrespro(dot)ru> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, pgsql-hackers(at)postgresql(dot)org, Justin Pryzby <pryzby(at)telsasoft(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Subject: | Re: using extended statistics to improve join estimates |
| Date: | 2024-05-20 08:52:07 |
| Message-ID: | 87o790kgj3.fsf@163.com |
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| Lists: | pgsql-hackers |
Hi Andrei,
> On 4/3/24 01:22, Tomas Vondra wrote:
>> Cool! There's obviously no chance to get this into v18, and I have stuff
>> to do in this CF. But I'll take a look after that.
> I'm looking at your patch now - an excellent start to an eagerly awaited
> feature!
> A couple of questions:
> 1. I didn't find the implementation of strategy 'c' - estimation by the
> number of distinct values. Do you forget it?
What do you mean the "strategy 'c'"?
> 2. Can we add a clauselist selectivity hook into the core (something
> similar the code in attachment)? It can allow the development and
> testing of multicolumn join estimations without patching the core.
The idea LGTM. But do you want
+ if (clauselist_selectivity_hook)
+ s1 = clauselist_selectivity_hook(root, clauses, varRelid, jointype,
+
rather than
+ if (clauselist_selectivity_hook)
+ *return* clauselist_selectivity_hook(root, clauses, ..)
?
--
Best Regards
Andy Fan
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