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From "Liu, Ming (Ming)" <ming....@esgyn.cn>
Subject RE: Upsert on part of columns get traf_merge which cause the performance not good
Date Wed, 06 Jun 2018 12:39:31 GMT
hi, Yuan,

You can check a discussion on this at https://lists.apache.org/list.html?user@trafodion.apache.org:2016-03,
search for 'upsert semantics' topic.
Default mode should be MERGE as discussed, it was decided that. Correct behavior is more important
than peformance.
I think you can create Non-Aligned format table, if the table is very frequently updated,
it will be slower for read queries though.

Others may have better answer here

thanks,
Ming

From: Liu, Yuan (Yuan) <yuan.liu@esgyn.cn>
Sent: Wednesday, June 06, 2018 3:33 PM
To: dev@trafodion.apache.org; user@trafodion.apache.org
Subject: Upsert on part of columns get traf_merge which cause the performance not good

Hi Trafodioneers,

In many cases, we find that "UPDATE" is not that efficient, so sometimes we rewrite the "UPDATE"
as "UPSERT".

However, if we only write part of columns in upsert, the query plan will get "TRAF_MERGE",
which is still not efficient.

Only if we write all the columns in upsert, the query plan can get good query plan, such as
VSBB_UPSERT.

If table has hundrends of columns, this is very complex for users.

It is possible that upsert choose "TRAF_REPLACE" by default, at the same time, we keep the
values which are not in upsert?


Best regards,
Yuan


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