Re: Compressed TOAST Slicing

On Wed, Feb 20, 2019 at 10:50 AM Daniel Verite <daniel@manitou-mail.org> wrote:
>
>         Paul Ramsey wrote:
>
> > Oddly enough, I couldn't find many/any things that were sensitive to
> > left-end decompression. The only exception is "LIKE this%" which
> > clearly would be helped, but unfortunately wouldn't be a quick
> > drop-in, but a rather major reorganization of the regex handling.
>
> What about starts_with(string, prefix)?
>
> text_starts_with(arg1,arg2) in varlena.c does a full decompression
> of  arg1 when it could limit itself to the length of the smaller arg2:

Nice catch, I didn't find that one as it's not user visible, seems to
be only called in spgist (!!)
./backend/access/spgist/spgtextproc.c:
DatumGetBool(DirectFunctionCall2(text_starts_with

Thanks, I'll add that.

P