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  1. IMPALA
  2. IMPALA-1788

Consider replacing constant exprs with literal equivalents

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      Evaluating expressions that are the same for every row can be very expensive (note these numbers are taken from the debug build, so maybe this is not an issue in release?):

      (15:33:02@desktop) ~/src/cloudera/impala (cdh5-trunk) $ impala-shell.sh -q "SELECT 1.2345678 FROM tpch.lineitem" -B 2>&1 > /dev/null
      ...
      Fetched 6001215 row(s) in 61.33s
      
      (15:34:06@desktop) ~/src/cloudera/impala (cdh5-trunk) $ impala-shell.sh -q "SELECT CAST('1.2345678' AS DOUBLE) FROM tpch.lineitem" -B 2>&1 > /dev/null
      ...
      Fetched 6001215 row(s) in 74.86s
      

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              alex.behm Alexander Behm
              henryr Henry Robinson
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