Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1h4B9X-0000EW-Fp for pgsql-hackers@arkaria.postgresql.org; Wed, 13 Mar 2019 21:11:07 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.89) (envelope-from ) id 1h4B9V-0000R1-Kr for pgsql-hackers@arkaria.postgresql.org; Wed, 13 Mar 2019 21:11:05 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1h4B9V-0000Qu-Dl for pgsql-hackers@lists.postgresql.org; Wed, 13 Mar 2019 21:11:05 +0000 Received: from sss.pgh.pa.us ([66.207.139.130]) by magus.postgresql.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1h4B9T-0002HX-D0 for pgsql-hackers@lists.postgresql.org; Wed, 13 Mar 2019 21:11:05 +0000 Received: from sss1.sss.pgh.pa.us (localhost [127.0.0.1]) by sss.pgh.pa.us (8.14.4/8.14.4) with ESMTP id x2DLAtvp016520; Wed, 13 Mar 2019 17:10:55 -0400 From: Tom Lane To: Andres Freund cc: Robert Haas , Alvaro Herrera , PostgreSQL Hackers Subject: Re: hyrax vs. RelationBuildPartitionDesc In-reply-to: <20190313205656.6eqpqua5vn4nf34d@alap3.anarazel.de> References: <7448.1552497345@sss.pgh.pa.us> <7961.1552498252@sss.pgh.pa.us> <10788.1552501588@sss.pgh.pa.us> <12316.1552504492@sss.pgh.pa.us> <14279.1552508314@sss.pgh.pa.us> <20190313205656.6eqpqua5vn4nf34d@alap3.anarazel.de> Comments: In-reply-to Andres Freund message dated "Wed, 13 Mar 2019 13:56:56 -0700" MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <16518.1552511455.1@sss.pgh.pa.us> Date: Wed, 13 Mar 2019 17:10:55 -0400 Message-ID: <16519.1552511455@sss.pgh.pa.us> List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk Andres Freund writes: > On 2019-03-13 16:50:53 -0400, Robert Haas wrote: >> On Wed, Mar 13, 2019 at 4:38 PM Robert Haas wrote: >>> On Wed, Mar 13, 2019 at 4:18 PM Tom Lane wrote: >>>> Off topic for the moment, since this clearly wouldn't be back-patch >>>> material, but I'm starting to wonder if we should just have a context >>>> for each relcache entry and get rid of most or all of the retail >>>> cleanup logic in RelationDestroyRelation ... >> It just occurred to me that one advantage of this would be that you >> could see how much memory was being used by each relcache entry using >> MemoryContextStats(), which seems super-appealing. > But it might also make it frustrating to look at memory context dumps - > we'd suddenly have many many more memory context lines we'd displayed, > right? Wouldn't that often make the dump extremely long? There's already a mechanism in there to suppress child contexts after 100 or so, which would almost inevitably kick in on the relcache if we did this. So I don't believe we'd have a problem with the context dumps getting too long --- more likely, the complaints would be the reverse. My gut feeling is that right now relcache entries tend to be mas-o-menos the same size, except for stuff that is *already* in sub-contexts, like index and partition descriptors. So I'm not that excited about this adding useful info to context dumps. I was just looking at it as a way to make relcache entry cleanup simpler and less leak-prone. Having said that, I do agree that CacheMemoryContext is too much of an undifferentiated blob right now, and splitting it up seems like it'd be good for accountability. I'd definitely be +1 for a catcache vs. relcache vs. other caches split. You could imagine per-catcache contexts, too. The main limiting factor here is that the per-context overhead could get excessive. regards, tom lane