Re: Queries containing ORDER BY and LIMIT started to work slowly

From: Rondat Flyag <rondatflyag(at)yandex(dot)ru>
To: Rick Otten <rottenwindfish(at)gmail(dot)com>
Cc: "pgsql-performance(at)lists(dot)postgresql(dot)org" <pgsql-performance(at)lists(dot)postgresql(dot)org>
Subject: Re: Queries containing ORDER BY and LIMIT started to work slowly
Date: 2023-08-30 17:46:46
Message-ID: 1062241693416677@mail.yandex.ru
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<div>Thanks for the response.</div><div>Sure, I thought about it and even bought another drive. The current drive is SSD, as far as I'm concerned write operations degrade SSDs.</div><div> </div><div>Even so, why other queries work fine? Why the query joining two tables instead of three works fine?</div><div> </div><div>Cheers,</div><div>Serg</div><div> </div><div>30.08.2023, 00:07, "Rick Otten" &lt;rottenwindfish(at)gmail(dot)com&gt;:</div><blockquote><div><div> </div> <div><div>On Tue, Aug 29, 2023 at 3:57 PM Rondat Flyag &lt;<a href="mailto:rondatflyag(at)yandex(dot)ru" rel="noopener noreferrer">rondatflyag(at)yandex(dot)ru</a>&gt; wrote:</div><blockquote style="border-left-color:rgb( 204 , 204 , 204 );border-left-style:solid;border-left-width:1px;margin:0px 0px 0px 0.8ex;padding-left:1ex"><div>I took the dump just to store it on another storage (external HDD). I didn't do anything with it.</div><div> </div><div>29.08.2023, 21:42, "Jeff Janes" &lt;<a href="mailto:jeff(dot)janes(at)gmail(dot)com" rel="noopener noreferrer" target="_blank">jeff(dot)janes(at)gmail(dot)com</a>&gt;:</div><blockquote><div><div> </div> <div><div>On Tue, Aug 29, 2023 at 1:47 PM Rondat Flyag &lt;<a href="mailto:rondatflyag(at)yandex(dot)ru" rel="noopener noreferrer" target="_blank">rondatflyag(at)yandex(dot)ru</a>&gt; wrote:</div><blockquote style="border-left-color:rgb( 204 , 204 , 204 );border-left-style:solid;border-left-width:1px;margin:0px 0px 0px 0.8ex;padding-left:1ex"><div>I have a legacy system that uses `Posgresql 9.6` and `Ubuntu 16.04`. Everything was fine several days ago even with standard Postgresql settings. I dumped a database with the compression option (maximum compression level -Z 9) in order to have a smaller size (`pg_dump --compress=9 database_name &gt; database_name.sql`). After that I got a lot of problems.</div></blockquote><div> </div><div>You describe taking a dump of the database, but don't describe doing anything with it.  Did you replace your system with one restored from that dump?  If so, did vacuum and analyze afterwards?</div><div> </div><div>Cheers,</div><div> </div><div>Jeff</div></div></div></blockquote></blockquote><div> </div><div>Since this is a very old system and backups are fairly I/O intensive, it is possible you have a disk going bad?  Sometimes after doing a bunch of I/O on an old disk, it will accelerate its decline.  You could be about to lose it altogether.</div><div> </div></div></div></blockquote>

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