[Devel] [Engine-devel] vds_dynamic refactor

[Liran Zelkha]

On Fri, Apr 4, 2014 at 3:15 PM, Itamar Heim <iheim at redhat.com> wrote:

> On 04/04/2014 04:30 AM, Liran Zelkha wrote:
>
>>
>>
>>
>> On Thu, Apr 3, 2014 at 8:40 PM, Gilad Chaplik <gchaplik at redhat.com
>> <mailto:gchaplik at redhat.com>> wrote:
>>
>>     ----- Original Message -----
>>      > From: "Liran Zelkha" <liran.zelkha at gmail.com
>>     <mailto:liran.zelkha at gmail.com>>
>>      > To: "Gilad Chaplik" <gchaplik at redhat.com
>>     <mailto:gchaplik at redhat.com>>
>>      > Cc: "Omer Frenkel" <ofrenkel at redhat.com
>>     <mailto:ofrenkel at redhat.com>>, "Eli Mesika" <emesika at redhat.com
>>     <mailto:emesika at redhat.com>>, "engine-devel" <engine-devel at ovirt.org
>>     <mailto:engine-devel at ovirt.org>>,
>>      > devel at linode01.ovirt.org <mailto:devel at linode01.ovirt.org>
>>      > Sent: Thursday, April 3, 2014 7:51:39 PM
>>      > Subject: Re: [Engine-devel] vds_dynamic refactor
>>      >
>>      > On Thu, Apr 3, 2014 at 5:33 PM, Gilad Chaplik
>>     <gchaplik at redhat.com <mailto:gchaplik at redhat.com>> wrote:
>>      >
>>      > > *From: *"Liran Zelkha" <liran.zelkha at gmail.com
>>     <mailto:liran.zelkha at gmail.com>>
>>
>>      > > *To: *"Gilad Chaplik" <gchaplik at redhat.com
>>     <mailto:gchaplik at redhat.com>>
>>
>>      > > *Cc: *"Omer Frenkel" <ofrenkel at redhat.com
>>     <mailto:ofrenkel at redhat.com>>, "Eli Mesika" <
>>      > > emesika at redhat.com <mailto:emesika at redhat.com>>, "engine-devel"
>>     <engine-devel at ovirt.org <mailto:engine-devel at ovirt.org>>
>>
>>      > > *Sent: *Thursday, April 3, 2014 5:27:56 PM
>>      > > *Subject: *Re: [Engine-devel] vds_dynamic refactor
>>      > >
>>      > > True but that's no reason to have a bad schema
>>      > >
>>      > > I'm open to new ideas and truly want to understand what is bad?
>>      > >
>>      > The problem is with both updates and selects.
>>      > For selects - to get all the information for the VDS we have
>> multiple
>>      > joins. Adding another one will hurt performance even more.
>>
>>     What about creating the VDS list in the db. i.e. your patch [1]
>>     about constructing VDS objects in the engine, should occur in the db
>>     within a SP, and should be transparent to the server. that will
>>     solve the multiple table join.
>>
>>
>> The joins are happening on the server. We have a VDS view that brings in
>> information from many tables and we retrieve rows from it all the time.
>> Just run an explain on a select * from vds and see for yourself.
>>
>
> thought the distinction was vds_static is updated by user (configuration),
> where as vds_dyanmic/statistics is reported from vdsm (slow/fast updates).
>
> True - vds_static hardly change. But vds_dynamic is split-brain - it has
practically static data, but also has the status - which changes rapidly.
And since we have 3 tables, we need to do 3 joins to get VDS (actually we
do much more).


> please remember joining them to one table, also means DWH will ETA all of
> data each time. today it will only copy statistics if dynamic did not
> change.
>
> I'm not saying joining all 3 tables to 1 table, just make them 2 tables.
And since the data is hardly changing - same logic of DWH will stay.
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