Re: Visibility map thoughts

"Heikki Linnakangas" <heikki@enterprisedb.com> writes:

> I don't buy that. I believe at least on some architectures you'd get a
> word-long load+modify+store, and scribble the neighboring bytes.

Hm, I mis-remembered this bit of advice from the glibc info doc. I remembered
thinking it was strange when I read it but I guess my memory exaggerated how
strange it was:

.>    In practice, you can assume that `int' is atomic. You can also assume
.> that pointer types are atomic; that is very convenient. Both of these
.> assumptions are true on all of the machines that the GNU C library supports
.> and on all POSIX systems we know of.

I suppose if we could keep count of tuples and a count of free space and use a
whole word. Map files would be 1M per 2G heap file (on an 8kb blocksize and
4-byte words). More complicated than necessary but I'm just thinking out loud.


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