From: Tom Lane <tgl@sss.pgh.pa.us>
To: Rick Otten <rottenwindfish@gmail.com>
cc: "pgsql-performa." <pgsql-performance@postgresql.org>
Subject: Re: max partitions behind a view?
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Comments: In-reply-to Rick Otten <rottenwindfish@gmail.com>
	message dated "Mon, 18 Sep 2017 07:25:14 -0400"
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Date: Mon, 18 Sep 2017 09:55:08 -0400
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Rick Otten <rottenwindfish@gmail.com> writes:
> The challenge is that because of an exponential rate of data growth, I
> might have to significantly increase the number of partitions I'm working
> with - to several hundred at a minimum and potentially more than 1000...

> This leads me to the question how many 'union all' statements can I have in
> one view?

I don't think there's a hard limit short of INT32_MAX or so, but I'd be
worried about whether there are any O(N^2) algorithms that would start
to be noticeable at the O(1000) level.

> Should I create a hierarchy of views to gradually roll the data
> up instead of putting them all in one top-level view?

That would likely make things worse not better; the planner would flatten
them anyway and would expend extra cycles doing so.  You could perhaps
stop the flattening with optimization fences (OFFSET 0) but I really doubt
you want the side-effects of that.

			regards, tom lane


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