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Wrong execution path

-klb
-klb Member Posts: 6
edited October 2010 in Python
Query going slow through cx_oracle

select ...
from big_table a, small_table b
where a.col1= :bind1
and a.col2 = :bind2
and a.col3 = :bind3
and a.col4 = :bind4
and a.col5 = b.col1

This query, when executed via SQLPLUS uses nested loops=>big table rowid via index range scan, with small table rowid index unique scan. Perfect, and very fast.

When going through python, it does a full table scan on big_table nested loops to the index unique scan on small-table.

Even with hint /*+ INDEX(a ix_on_those_columns) */, the query from python does a full table scan against the oracle table.

The statistics are up to date on the objects.

What could be causing this?

Thanks,

Answers

  • 734879
    734879 Member Posts: 121
    Try adding...

    conn.cursor().execute("alter session set events '10046 trace name context forever, level 12'")

    ...before you execute the query. Format the trace file using tkprof and the issue will usually jump out at you.

    HTH,

    Steve
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