Re: strncmp->memcmp when we know the shorter length

On Mon, Dec 20, 2010 at 1:10 PM, Noah Misch <noah@leadboat.com> wrote:
> When the caller knows the smaller string length, memcmp and strncmp are
> functionally equivalent.  Since memcmp need not watch each byte for a NULL
> terminator, it often compares a CPU word at a time for better performance.  The
> attached patch changes use of strncmp to memcmp where we have the length of the
> shorter string.  I was most interested in the varlena.c instances, but I tried
> to find all applicable call sites.  To benchmark it, I used the attached
> "bench-texteq.sql".  This patch improved my 5-run average timing of the SELECT
> from 65.8s to 56.9s, a 13% improvement.  I can't think of a case where the
> change should be pessimal.

This is a good idea.  I will check this over and commit it.

--
Robert Haas
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