From: Andrei Lepikhov <lepihov@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org, akorotkov@postgresql.org, Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Subject: Re: BUG #19102: Assertion failure in generate_orderedappend_paths with aggregate pushdown
Date: Tue, 4 Nov 2025 14:43:05 +0100
Message-ID: <e90abc7c-3d59-4f7b-9def-e43c4a6d587e@gmail.com> (raw)
In-Reply-To: <CAMbWs49ONLr4-_X3xe5nMgy-Jaqju_Cn0osaj3RMSsV-9Pd2Cg@mail.gmail.com>
References: <19102-93480667e1200169@postgresql.org>
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<CAMbWs49ONLr4-_X3xe5nMgy-Jaqju_Cn0osaj3RMSsV-9Pd2Cg@mail.gmail.com>
On 4/11/2025 08:44, Richard Guo wrote:
> Any thoughts?The first patch looks good, but I still have a couple of questions.
1. We don't use parameterised paths in MergeAppend yet. I wonder if it
could be nudged by spreading the use of partitioned tables with foreign
partitions. Do you think, in such a case, the usage of
cheapest_total->rows will stay correct? It seems that the parameterised
path has much less estimation than the RelOptInfo...
2. I understand why the upper relation has unset nrows. However, it may
be more accurate to set row estimation for a pushing-down upper
RelOptInfo. Or, at least, describe in comments why this is desirable
behaviour. It would be profitable, at least, for extension developers.
I also support the second patch. With many partitions, it allows us to
save a significant amount of CPU cycles.
--
regards, Andrei Lepikhov,
pgEdge
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To: pgsql-bugs@postgresql.org
Cc: lepihov@gmail.com, guofenglinux@gmail.com, kuntalghosh.2007@gmail.com
Subject: Re: BUG #19102: Assertion failure in generate_orderedappend_paths with aggregate pushdown
In-Reply-To: <e90abc7c-3d59-4f7b-9def-e43c4a6d587e@gmail.com>
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