On 1/7/17 10:01 PM, Peter Geoghegan wrote:
> It occurs to me that the comparison caching stuff added by commit
> 0e57b4d8b needs to be considered here, too. When we had to copy the
> string to a temp buffer anyway, in order to add the terminating NUL
> byte expected by strcoll(), there was an opportunity to do caching of
> comparisons at little additional cost. However, since ICU offers an
> interface that you're using that doesn't require any NUL byte, there
> is a new trade-off to be considered -- swallow the cost of copying
> into our own temp buffer solely for the benefit of comparison caching,
> or don't do comparison caching. (Note that glibc had a similar
> comparison caching optimization itself at one point, built right into
> strcoll(), but it was subsequently disabled.)

That might be worth looking into, but it seems a bit daunting to
construct a benchmark specifically for this, unless we have the one that
was originally used lying around somewhere.

Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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