[EMAIL PROTECTED] wrote:
Is it worth the effort to pre-process the pattern?
For example:
%% -> %
This is already done, required by spec.
%_ -> _%
If applied recursively, this would automatically cover:
%_% -> _%
_%_ -> __%
The 'benefit' would be that the pattern matching code would not
need an inner if statement?
I doubt it's worth the trouble.
Also - I didn't see a response to my query with regard treating UTF-8
as a two pass match. First pass treating it as bytes. If the first pass
matches, the second pass doing a full analysis. In the case of low
selectivity, this will be a win, as the primary filter would be the
full speed byte-based matching.
All matching will now be done byte-wise. CHAREQ is dead.
Advancing will also be done byte-wise except for:
. where text matching is against _ for UTF8
. where text matching is against % or _ for other multi-byte charsets.
So two passes doesn't sound like much of a win.
I had also asked why the focus would be on high selectivity. Why would
the primary filter criteria for a properly designed select statement by
a like with high selectivity? The only time I have ever used like is
when I expect low selectivity. Is there a reasonable case I am missing?
I think you'd need to show something close to a Pareto improvement:
nobody worse off and some people better off. If you can do that then
send in a patch.
However, I'm trying to minimise special case processing for UTF8, not
create a whole new code path for it. The less special cases we have the
easier it will be to maintain.
cheers
andrew
---------------------------(end of broadcast)---------------------------
TIP 2: Don't 'kill -9' the postmaster
