postgres-xc-developers Mailing List for Postgres-XC

I looked at the schedule.

I am not sure about the planned design for GROUP BY, but originally
Andrei was planning on making it somewhat similar to ORDER BY, how
ORDER BY does a merge sort on the coordinator, based on sorted results
from the data nodes. Each data node could do the beginning phase of
aggregation in groups and then sort the output in the same manner of
the groups. Then, the coordinator could do the last step of
aggregation with like groups, which is easy to get them on the fly
because of the sorting coming in from the data nodes (and avoiding
materialization).

This should work pretty well.  One drawback is if they chose a GROUP
BY clause with many groups (many = thousands+). Then some parallelism
is lost because of the final phase being done in only one place, on
the Coordinator. GridSQL spreads out the final aggregation phase
amongst all the data nodes, moving like groups to the same node to get
more parallelism. I think row shipping infrastructure might have to be
in place first before implementing that, and there will be a
noticeable benefit only once there are many, many groups, so I don't
see it being a critical thing at this phase and can be added later.

Regards,

Mason



On Thu, Apr 7, 2011 at 5:27 AM, Koichi Suzuki
<koi...@us...> wrote:
> Project "Postgres-XC documentation".
>
> The branch, master has been updated
>       via  62434399fdd57aff2701e3e5e97fed619f6d6820 (commit)
>      from  252519c2be5309a3682b0ee895cf040083ae1784 (commit)
>
>
> - Log -----------------------------------------------------------------
> commit 62434399fdd57aff2701e3e5e97fed619f6d6820
> Author: Koichi Suzuki <koi...@gm...>
> Date:   Thu Apr 7 18:27:26 2011 +0900
>
>    1. Added 2011FYQ1 schedule for each member.
>    2. Modified my progress sheet of Reference Manual.
>
>                     -- Koichi Suzuki
>
> diff --git a/progress/2011FYQ1_Schedule.ods b/progress/2011FYQ1_Schedule.ods
> new file mode 100755
> index 0000000..5e24d37
> Binary files /dev/null and b/progress/2011FYQ1_Schedule.ods differ
> diff --git a/progress/documentation-progress.ods b/progress/documentation-progress.ods
> index 277aade..2c8577e 100644
> Binary files a/progress/documentation-progress.ods and b/progress/documentation-progress.ods differ
>
> -----------------------------------------------------------------------
>
> Summary of changes:
>  progress/2011FYQ1_Schedule.ods      |  Bin 0 -> 22147 bytes
>  progress/documentation-progress.ods |  Bin 16883 -> 19519 bytes
>  2 files changed, 0 insertions(+), 0 deletions(-)
>  create mode 100755 progress/2011FYQ1_Schedule.ods
>
>
> hooks/post-receive
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I added the latest version of the patch in the patch tracker.
-- 
Thanks,

Michael Paquier
http://michael.otacoo.com

Hi,

Just to let everybody know about the status of DBT-1 with latest Postgres-XC
release...

Related to bug 3240359 and some others, it is important to know that
runnning DBT-1 with version 0.9.4 may result in a high number of errors.
The origin of this problem is the aggregate function count.
Because of the fact that when doing a count XC returns 0 rows instead of 1
row with 0 as result, this is resulting in a huge amount of errors when
running DBT1.
So basically we are unable to make proper DBT-1 measurements with 0.9.4.

The query being the origin of the error is from addToSC.h:
SELECT count(scl_sc_id)
FROM   shopping_cart_line
WHERE  scl_sc_id=%lld;
-- 
Thanks,

Michael Paquier
http://michael.otacoo.com

Benny;

I'm afraid I didn't find the the patch attached.   I'll register it to
the patch track for the review.

Thank you;
----------
Koichi Suzuki



2011/4/6 wangxiong.gm <wan...@gm...>:
>
> Dears,
>
> When a table is dropped, the relative distribution information will be kept
> in pgxc_class catalog now. The patch can fix such a problem. The relative
> infomation on the table distribution will be removed when drop a table.
>
> I hope it's helpful.
>
> Best regards,
> Benny
> 2011-04-06
> ________________________________
> wangxiong.gm
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