From: Andrei Lepikhov <lepihov@gmail.com>
To: David Rowley <dgrowleyml@gmail.com>
Cc: tharakan@gmail.com, pgsql-bugs@lists.postgresql.org, PG Bug reporting form <noreply@postgresql.org>
Cc: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Tomas Vondra <tomas@vondra.me>
Subject: Re: BUG #18885: ERROR: corrupt MVNDistinct entry - 2
Date: Tue, 15 Apr 2025 11:41:08 +0200
Message-ID: <048f142e-18eb-4416-b7c7-b1398e667b3c@gmail.com> (raw)
In-Reply-To: <CAApHDvocZCUhM9W9mJ39d6oQz7ePKoqFnao_347mvC-A7QatcQ@mail.gmail.com>
References: <18885-da51324078588253@postgresql.org>
<f485c85f-9796-467e-81fe-43e8127cbb35@vondra.me>
<CAApHDvocZCUhM9W9mJ39d6oQz7ePKoqFnao_347mvC-A7QatcQ@mail.gmail.com>
On 4/14/25 01:26, David Rowley wrote:
> just "continue;". The variable would only be needed if there was some
> inner loop and we couldn't use "continue".
+1
> * XXX Maybe we should allow searching the expressions even if we
> * found an attribute matching the expression? That would handle
> * trivial expressions like "(a)" but it seems fairly useless.
> */
> Maybe it meant "matching the Var"?
+1
I have read your modification of comments to
estimate_multivariate_ndistinct. It suggested the idea of letting the
GroupVarInfo struct be exported. For now, only add_unique_group_var or
another internal selfuncs.c routine may build this list.
I'm not sure that the GroupVarInfo abstraction is shaped ideally at the
moment, but it seems it may perform duties similar to RestrictInfo but
for grouping keys: store the key, cache data about this key, cache
statistics and estimations.
It would be the first step in letting modules use
estimate_multivariate_ndistinct. Likewise, we can use
statext_clauselist_selectivity and dependencies_clauselist_selectivity.
What do you think about that?
P.S. statext_mcv_clauselist_selectivity deserves to be exported, too.
--
regards, Andrei Lepikhov
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Subject: Re: BUG #18885: ERROR: corrupt MVNDistinct entry - 2
In-Reply-To: <048f142e-18eb-4416-b7c7-b1398e667b3c@gmail.com>
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