Re: Fast bitwise search

Richard Kuhler <noone_at_nowhere.com> wrote:
> kuntz.1507173_at_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

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