Subject Re: ORDER BY on large VARCHAR columns
Author robert_difalco
<unordained_00@c...> wrote:
> ... they can't be chopped up -and- indexing just the first 250 or
so chars wouldn't at least help
> somewhat? in theory it would reduce by orders of magnitude how
many comparisons would be needed,
> even if the index couldn't do the entire sort by itself ... or,
heck, four or five varchar fields,
> using substring? doesn't need to be hierarchical, you've got a set
limit on the length ...

Well, I have a UDF to perform regex searches on this column, so I
can't really split them up as I have no idea where the wildcards may
be in the search pattern. It's just a very problematic field.

Also, there is a requirement that they be displayed -- fully
qualified, sorted, and paged (i.e. 15-20 at a time).

Can Firebird use a partial (i.e. substring) INDEX and have that
index help it sort this table? I didn't think so, but maybe I'm not
sure what you mean by "indexing just the first 250 or so chars".