From: Brendan Duddridge <brendan@clickspace.com>
To: Jim C. Nasby <jnasby@pervasive.com>
Cc: Greg Stark <gsstark@mit.edu>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: App very unresponsive while performing simple update
Date: Wed, 31 May 2006 00:29:50 -0600
Message-ID: <09F270C9-7DF8-4574-AC70-CD7F9DA2C020@clickspace.com> (raw)
In-Reply-To: <20060531062307.GG53487@pervasive.com>
References: <961F6F02-4B00-494C-B071-6DF76A305C14@clickspace.com>
<21B15664-F4EE-462C-88B4-EEEB2B4A979F@clickspace.com>
<874pzanvk6.fsf@stark.xeocode.com>
<17733.1148832292@sss.pgh.pa.us>
<3C756C36-DC66-4D13-B2CE-99CFCE7BF390@clickspace.com>
<87hd39n3c4.fsf@stark.xeocode.com>
<20060531062307.GG53487@pervasive.com>
>> You should realize this will produce a lot of garbage records and
>> mean you'll
>> have to be running vacuum very frequently. You might consider
>> instead of
>> updating the main table inserting into a separate clickstream
>> table. That
>> trades off not getting instantaneous live totals with isolating the
>> maintenance headache in a single place. That table will grow large
>> but you can
>> prune it at your leisure without impacting query performance on
>> your main
>> tables.
We actually already have a table for this purpose. product_click_history
>
> Actually, you can still get instant results, you just have to hit two
> tables to do it.
Well, not really for our situation. We use the click_count on product
to sort our product listings by popularity. Joining with our
product_click_history to get live counts would be very slow. Some
categories have many tens of thousands of products. Any joins outside
our category_product table tend to be very slow.
We'll probably have to write a process to update the click_count from
querying our product_click_history table.
____________________________________________________________________
Brendan Duddridge | CTO | 403-277-5591 x24 | brendan@clickspace.com
ClickSpace Interactive Inc.
Suite L100, 239 - 10th Ave. SE
Calgary, AB T2G 0V9
http://www.clickspace.com
On May 31, 2006, at 12:23 AM, Jim C. Nasby wrote:
> On Sun, May 28, 2006 at 07:20:59PM -0400, Greg Stark wrote:
>> Brendan Duddridge <brendan@clickspace.com> writes:
>>
>>> We do have foreign keys on other tables that reference the
>>> product table.
>>> Also, there will be updates going on at the same time as this
>>> update. When
>>> anyone clicks on a product details link, we issue an update
>>> statement to
>>> increment the click_count on the product. e.g. update product
>>> set click_count
>>> = click_count + 1;
>>
>> You should realize this will produce a lot of garbage records and
>> mean you'll
>> have to be running vacuum very frequently. You might consider
>> instead of
>> updating the main table inserting into a separate clickstream
>> table. That
>> trades off not getting instantaneous live totals with isolating the
>> maintenance headache in a single place. That table will grow large
>> but you can
>> prune it at your leisure without impacting query performance on
>> your main
>> tables.
>
> Actually, you can still get instant results, you just have to hit two
> tables to do it.
>
>> More likely you were blocking on some lock. Until that other query
>> holding
>> that lock tries to commit Postgres won't actually detect a
>> deadlock, it'll
>> just sit waiting until the lock becomes available.
>
> Wow, are you sure that's how it works? I would think it would be
> able to
> detect deadlocks as soon as both processes are waiting on each other's
> locks.
> --
> Jim C. Nasby, Sr. Engineering Consultant jnasby@pervasive.com
> Pervasive Software http://pervasive.com work: 512-231-6117
> vcard: http://jim.nasby.net/pervasive.vcf cell: 512-569-9461
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 5: don't forget to increase your free space map settings
>
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To: pgsql-performance@postgresql.org
Cc: brendan@clickspace.com, jnasby@pervasive.com, gsstark@mit.edu, tgl@sss.pgh.pa.us
Subject: Re: App very unresponsive while performing simple update
In-Reply-To: <09F270C9-7DF8-4574-AC70-CD7F9DA2C020@clickspace.com>
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