[jira] [Created] (IMPALA-13166) Queries with many nested views are still slow

["Michael Smith (Jira)" <ji...@apache.org>]

Michael Smith created IMPALA-13166:
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             Summary: Queries with many nested views are still slow
                 Key: IMPALA-13166
                 URL: https://issues.apache.org/jira/browse/IMPALA-13166
             Project: IMPALA
          Issue Type: Improvement
          Components: Frontend
    Affects Versions: Impala 4.4.0
            Reporter: Michael Smith


Further profiling on the query from IMPALA-12800 - and a larger version of the same - show significant time spent in {{Analyzer#registerSlotRef}}. The bulk of the work here is in checking whether a {{SlotDescriptor}} exists in the current {{TupleDescriptor}}, both because {{Path#getFullyQualifiedRawPath}} is expensive and because equals on the resulting list is expensive (especially repeated over every {{SlotDescriptor}} in the {{TupleDescriptor}}.

There's room for improvement here:
1. avoid copying {{rawPath_}} every time we call {{getFullyQualifiedRawPath}}
2. use a map to identify whether a {{SlotDescriptor}} already exists at {{Path}} in the current {{TupleDescriptor}}
3 other small improvements may exist around memory allocation



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