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2098977 - ORDER BY clause causing query to take longer - SAP ASE

Symptom

  • You are running a query with a UNION ALL clasue and an ORDER BY clause.
  • Without ORDER BY the query runs fast.
  • When appending ORDER BY on a column that is already indexed, the query takes considerably longer to execute.
  • When ORDER BY is used, the query plan shows that the optimizer is spending a lot of time in sorting of a worktable.
  • ASE is configured with the optimization goal "allrows_oltp".


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Environment

SAP Adaptive Server Enterprise (ASE) 15.x

Product

SAP Adaptive Server Enterprise 15.7 ; Sybase Adaptive Server Enterprise 15.0 ; Sybase Adaptive Server Enterprise 15.5

Keywords

allrows_mix, allrows_dss, join, nested-loop, hash-joins, merge-joins, optgoal, performance , KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Problem

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