• Ramil Kalimullin's avatar
    Fix for bug#52051: Aggregate functions incorrectly returns · 18e4d1ae
    Ramil Kalimullin authored
          NULL from outer join query
          
          Problem: optimising MIN/MAX() queries without GROUP BY clause
          by replacing the aggregate expression with a constant, we may set it
          to NULL disregarding the fact that there may be outer joins involved.
          
          Fix: don't replace MIN/MAX() with NULL if there're outer joins.
          
          Note: the fix itself is just
          - if (!count)
          + if (!count && !outer_tables)
              set to NULL
          
          The rest of the patch eliminates repeated code to improve speed
          and for easy maintenance of the code.
    
    
    mysql-test/r/group_by.result:
              Fix for bug#52051: Aggregate functions incorrectly returns
              NULL from outer join query
                - test result.
    mysql-test/t/group_by.test:
              Fix for bug#52051: Aggregate functions incorrectly returns
              NULL from outer join query
                - test case.
    sql/opt_sum.cc:
              Fix for bug#52051: Aggregate functions incorrectly returns
              NULL from outer join query
                - optimising MIN/MAX() queries without GROUP BY clause by
              replacing them with a constant, take into account that
              there're may be outer joins involved.
                - repeated code for MIN/MAX optimization in the opt_sum_query()
              eliminated by introducing new functions that read MIN/MAX values
              using index and combining MIN/MAX cases to one.
    18e4d1ae
group_by.result 55.4 KB