Using SIMD instructions (MMX/SSE/AVX)
○ Most operators limited to floats but recently more general purpose (integer) vector operations have been supported
○ Registers keep increasing in size -- the next generation of CPUs will have 512 byte registers which may be sufficient
For SSE/MMX/AVX/etc or GPU sorts it would have to use integer or floating point surrogate keys. It would probably be the same abbreviated keys mentioned in the last few slides. That could be a radix sort but generally I think bitonic sort is preferred.
That's not quite true. It supports string tries, for example (using SP-GIST). Such operations just have to be built for specific types. I think it would be more accurate to say that (AFAICT) Postgres doesn't currently have any way to extend the optimizer with custom plans (though it's been a very popular feature suggestion).