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change of pushdown behavior after upgrade to DS 4.2.11


 
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skromoka1970
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Joined: 01 Jan 2019

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PostPosted: Tue Jan 01, 2019 3:45 pm 
Post subject: change of pushdown behavior after upgrade to DS 4.2.11

Hi,

two weeks ago the client has upgraded from SAP DS 4.2.9 to 4.2.11 Patch 1. (oracle12 as underlying database, Job server on AIX)

The upgrade went fine but we observe that pushdown behaviour does not seem to work as expected anymore. We have tried to identify the major differences based on the following case :

two input tables with each one query transform (with no transformations), these two query transforms are inner joined, followed by one query transform which contains a database function (decode) and one target table.

- previously this dataflow was pushed down, after the upgrade not anymore. Pushdown for this case now only is achieved when the decode function is moved to the query transform where the join is done.

- When inner join of two tables are done, without any query transforms before the join, then pushdown is achieved (with a database function in the query transform subsequent to the join query transform) again. This also is the case when a table and a query transform is inner joined.

- When a left outer join is done between tables, then pushdown is achieved, when a left outer join is down and either one of the inputs involves a query transform, then pushdown is lost.

To summarize: pushdown of dataflows with (database) transformation functions is achieved without problems when only tables are (inner or left) joined. As soon as one of the inputs of the join contain a query transform, pushdown is lost, when a database function (nvl, decode, sysdate, etc) is used.

We are still investigating the scope of this change in behaviour but based on what we have seen sofar this is heavily influencing flows that have been built already, and more important, the future possibilities of designing data flows with pushdown.

Has anybody come across something similar lately ? We have raised an incident at SAP but we find it hard to believe that this would be unnoticed at other clients, esspecially where production flows might be affected by this change in behaviour.

PS. All conditions regarding pushdown optimization are met (all tables in same datastore etc), as we have already implemented a lot of dataflows to allow processing of 100+ million records. A lot of these dataflows have lost pushdown after the upgrade.
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