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Hana SQL Query on composite provider ends with OOM

Hi,

Our BW team reported issue on following query which results in OOM.

Select top 1000 * from "ZSALES_MART_5642"."SWEDEN::C_SORD_INT99";

From the OOM file we can see allocator "Pool/JoinEvaluator/JERequestedAttributes/Results" is taking almost 100GB of memory. Though underlying tables for above query are very small like 25MB and 7MB.

So I'm not sure why joins on those 2 tables and few other can consume 100GB and still fails.

Please bear with me my little knowledge on sql side.

Attached screenshot of Visualiser Planvisplan.png

.. couldn't upload the full plan as it's not allowed.

Looking forward to gain some ideas from your expertise!!

Thanks

visplan.png (44.6 kB)
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  • Posted on Jul 27, 2020 at 12:17 PM

    - Take a look at how this view/cp is created and if there are any performance bottlenecks in them which is why its causing this issue

    - How many columns are you querying and why select *? this to me dosent look like an ideal query. You could try to query only those columns that you need and check if its still bad

    - Do backtracking to identify the exact performance bottleneck, do this either bottom to top or vice versa by running the query on the supporting tables/views projection nodes from top/bottom

    Thanks

    Abhishek Shanbhogue

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