ctcgag@hotmail.com wrote:
> Richard Kuhler <noone@nowhere.com> wrote:
>
>>kuntz.1507173@bloglines.com wrote:
>>
>>>we have a large table that contains a bitmask field:
>>>MASK NUMBER(19)
>>>
>>>The application then performs a query that includes BITAND(MASK, ?) > 0
>>>condition.
>>>
>>>Is there any way to use an index for this condition. I was thinking
>>>about bitmap indexes for this but could not figure out how to use them
>>>here.
>>
>>Why in the world would you bundle data up into a column like that? I
>>can't imagine why the correct solution isn't to break those bits out
>>into individual columns with descriptive names so people can actually
>>see what information is stored there. Then you could use bitmap indexes
>>on them if performance dictated it (keeping in mind the problems they
>>create).
>
> I don't know why the OP would bundle data up like that, but I do it because
> N+512 columns in a table is just too many, and N+2048 columns is way too
> many. (Of course, I have little hopes of getting bitmap indices to work
> effectively on this data anyway.)
>
> Xho

Wow, you really have a tuple with 2048 distinct and meaningful
attributes? What is this application if I might ask? Even if you
convinced me that they absolutely can't be columns, I'd wonder why they
can't be rows in a related table.

--
Richard Kuhler