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Posted to user@trafodion.apache.org by "Liu, Yuan (Yuan)" <yu...@esgyn.cn> on 2017/07/28 07:57:29 UTC

Do we have cqd to force MDAM?

Hi Trafodioneers,

Does anyone know that do we have any cqd to force MDAM query plan? Cqd mdam_scan_method 'on' seems not work.

Best regards,
Yuan
Email: yuan.liu@esgyn.cn<ma...@esgyn.cn>
Cellphone: (+86) 13671935540

RE: Do we have cqd to force MDAM?

Posted by "Liu, Yuan (Yuan)" <yu...@esgyn.cn>.

Thank you, Suresh.


Best regards,
Yuan
Email: yuan.liu@esgyn.cn<ma...@esgyn.cn>
Cellphone: (+86) 13671935540

From: Suresh Subbiah [mailto:suresh.subbiah60@gmail.com]
Sent: Saturday, July 29, 2017 11:27 AM
To: user@trafodion.incubator.apache.org
Subject: Re: Do we have cqd to force MDAM?

Hi Yuan,

We don't have a cqd to force mdam for all scans in a given query.
MDAM_SCAN_METHOD has 3 possible value; ON, OFF and MAXIMUM. ON is the default. If cqd is set to MAXIMUM mdam scan on the right side of  a nested join is considered.
The cqd in all three settings will only influence whether mdam is considered. It still has to win under the cost model to be chosen.

With a Control query shape we can force mdam as you know. I think we can also a control table statement, though I have not done this recently.

Since CQS syntax can get quite unwieldy, I am think of creating a JIRA  asking that <<+ mdam(col-list)>> type hints be supported to force index access. The problem with a cqd I think is that there could several scans in one query and maybe we don't want mdam for all of them.

Thanks
Suresh


On Fri, Jul 28, 2017 at 2:57 AM, Liu, Yuan (Yuan) <yu...@esgyn.cn>> wrote:
Hi Trafodioneers,

Does anyone know that do we have any cqd to force MDAM query plan? Cqd mdam_scan_method ‘on’ seems not work.

Best regards,
Yuan
Email: yuan.liu@esgyn.cn<ma...@esgyn.cn>
Cellphone: (+86) 13671935540<tel:+86%20136%207193%205540>

Re: Do we have cqd to force MDAM?

Posted by Suresh Subbiah <su...@gmail.com>.

Hi Yuan,

We don't have a cqd to force mdam for all scans in a given query.
MDAM_SCAN_METHOD has 3 possible value; ON, OFF and MAXIMUM. ON is the
default. If cqd is set to MAXIMUM mdam scan on the right side of  a nested
join is considered.
The cqd in all three settings will only influence whether mdam is
considered. It still has to win under the cost model to be chosen.

With a Control query shape we can force mdam as you know. I think we can
also a control table statement, though I have not done this recently.

Since CQS syntax can get quite unwieldy, I am think of creating a JIRA
 asking that <<+ mdam(col-list)>> type hints be supported to force index
access. The problem with a cqd I think is that there could several scans in
one query and maybe we don't want mdam for all of them.

Thanks
Suresh

On Fri, Jul 28, 2017 at 2:57 AM, Liu, Yuan (Yuan) <yu...@esgyn.cn> wrote:

> Hi Trafodioneers,
>
>
>
> Does anyone know that do we have any cqd to force MDAM query plan? Cqd
> mdam_scan_method ‘on’ seems not work.
>
>
>
> Best regards,
>
> Yuan
>
> Email: yuan.liu@esgyn.cn
>
> Cellphone: (+86) 13671935540 <+86%20136%207193%205540>
>
>
>

FW: Do we have cqd to force MDAM?

Posted by "Liu, Yuan (Yuan)" <yu...@esgyn.cn>.

Hi Trafodioneers,

Does anyone know that do we have any cqd to force MDAM query plan? Cqd mdam_scan_method 'on' seems not work.

Best regards,
Yuan
Email: yuan.liu@esgyn.cn<ma...@esgyn.cn>
Cellphone: (+86) 13671935540