• evgen@moonbone.local's avatar
    Fixed bug #18360: Type aggregation for IN and CASE may lead to a wrong · 9fc769ff
    evgen@moonbone.local authored
    result
    
    The IN function aggregates result types of all expressions. It uses that 
    type in comparison of left expression and expressions in right part. 
    This approach works in most cases. But let's consider the case when the
    right part contains both strings and integers. In that case this approach may
    cause wrong results because all strings which do not start with a digit are
    evaluated as 0.
    CASE uses the same approach when a CASE expression is given thus it's also
    affected.
    
    The idea behind this fix is to make IN function to compare expressions with
    different result types differently. For example a string in the left
    part will be compared as string with strings specified in right part and
    will be converted to real for comparison to int or real items in the right
    part.
    
    A new function called collect_cmp_types() is added. It collects different
    result types for comparison of first item in the provided list with each 
    other item in the list. 
    
    The Item_func_in class now can refer up to 5 cmp_item objects: 1 for each
    result type for comparison purposes. cmp_item objects are allocated according
    to found result types. The comparison of the left expression with any
    right part expression is now based only on result types of these expressions.
    
    The Item_func_case class is modified in the similar way when a CASE
    expression is specified. Now it can allocate up to 5 cmp_item objects
    to compare CASE expression with WHEN expressions of different types.
    The comparison of the CASE expression with any WHEN expression now based only 
    on result types of these expressions.
    9fc769ff
item_cmpfunc.h 45.3 KB