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From: Andy Fan <[email protected]>
To: Andrei Lepikhov <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Julien Rouhaud <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: [email protected]
Cc: Justin Pryzby <[email protected]>
Cc: [email protected]
Subject: Re: using extended statistics to improve join estimates
Date: Mon, 20 May 2024 16:52:07 +0800
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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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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