Jeff Davis wrote:
On Tue, 2009-12-15 at 10:19 -0500, Tom Lane wrote:
I'm not sure that anyone has argued that. I did suggest that there
might be a small list of types for which we should provide discrete
behavior (ie, with next/previous functions) and the rest could have
continuous behavior (without that assumption). But I quite agree
that we want both types of ranges.
It seems like we're moving toward treating TIMESTAMP as continuous.
If I'm correct, continuous ranges always need two extra bits of storage
for the exclusivity. But for timestamps, that means 16 bytes (2 x 8-byte
timestamp) turns into 17 bytes, which is really more like 20 or 24 bytes
with alignment.
Considering that these are likely to be used for audit or history
tables, 8 bytes of waste (50%) seems excessive -- especially when
treating them as discrete seems to work pretty well, at least for the
int64 timestamps.
Would it be OK if we handled float timestamp ranges as continuous and
int64 timestamps discrete? You effectively lose the ability to build
non-contiguous sets with continuous ranges. Which is integral to the
work I'm doing (union, intersect, coalesce and minus sets of ranges)
As for the extra bits, would it be better to just require continuous
ranges to be either [] or [)? But I don't know which would be preferred.
My inclination would be toward [), but Tom seemed to indicate that
perhaps [] was the norm.
Scott
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