Re: bug of pg_trgm?

On Thu, Aug 9, 2012 at 3:05 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> ... btw, I think there is another problem here, which is that
> generate_wildcard_trgm will restart get_wildcard_part at the
> same place that the second loop exits, which means it would
> do the wrong thing if what it returns is a pointer to the
> second char of an escape pair. Consider for instance
>
> foo\\%bar
>
> The first call of get_wildcard_part will correctly extract "foo",
> but then return a pointer to the second backslash. So the second
> call will think that the % is escaped, which it is not, leading to
> a wrong decision about whether to pad "bar".

Good catch!

> Probably a minimal fix for this could be made by backing up "endword"
> one byte before returning it if in_escape is true when the second
> loop exits. That would not scale up to preserving the state of
> in_wildcard_meta, but since the second loop never advances past a
> meta char, that's okay for the moment.

Or what about extending get_wildcard_part() so that it accepts the pointer
to in_escape as an argument? generate_wildcard_trgm() can know the last
value of in_escape and specify it the next call of get_wildcard_part(). Looks
very simple.

Regards,

--
Fujii Masao