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2696356 - IQ could run slower with more temp cache on a Windows - SAP IQ

Symptom

  • IQ could run slower with more temp cache on a Windows.
  • 2 tests below were performed for the same query, one test with -iqtc 100000 and another test with iqtc 400000. It results that the query is slower with higher iqtc.

With -iqtc 100000
The Fast query plan has at #134 a Parallel Combiner that has drained the rows, from 49,530,598 rows to 0 rows.
Est. Temp Space Used (Mb) 660619.5
Act. Temp Space Used (Mb) 20484.5
38 secs to complete

With -iqtc 400000
In the Slow query plan the Parallel Combiner node does not exist.
Est. Temp Space Used (Mb) 5152.0
Act. Temp Space Used (Mb) 28575.0
4min 39 secs to complete


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Environment

SAP IQ 16.1

Product

SAP IQ 16.1

Keywords

CR816748, CR#816748, 816748, performance, slow, slower, memory, iqtc, -iqtc, max_hash_rows, , KBA , BC-SYB-IQ , Sybase IQ , Bug Filed

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