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Question and Answer

Connor McDonald

Thanks for the question, Mark.

Asked: January 27, 2017 - 4:29 pm UTC

Last updated: January 30, 2017 - 8:03 pm UTC

Version: 12C

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You Asked

We have a few tables that have just under 255 columns. According to Oracle documentation, the max number of columns that can be stored in a block is 255. If Extended stats are produced for this table, which creates additional hidden columns, could this cause the row to spill into an additional block. I realize it is only an issue on "select *" queries, but we do have some of these in our applications.

Thanks!!

and Connor said...

By default, there is no means to do so in 12.1, but there is in 12.2. This was logged as bug 21171382 so you can contact Support to request a backport of the patch if needed.

If you want to turn it off system wide, you can do that - but you need to get Support's endorsement for that, because its an underscore parameter.

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A question about extended Stat and exchange partition

Gh, January 28, 2017 - 6:37 am UTC

Reading this spot I have a doubt.
How overcome issue when gathering extended stats on some cols in partitioned table. Since system cols are generated the exchange partition will fail cause #of cols do not match with the exchanged table.
Yes we have to make them unused cols.
Still this is tricky ..not practical industrial thing.
Any suggestions?
Connor McDonald
January 30, 2017 - 8:03 pm UTC

Some means to work with that here

https://connormcdonald.wordpress.com/2013/01/20/exchange-partition-those-pesky-columns/

In 12.2, you can just do

create table T for exchange as ...
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