On Nov 25, 2008, at 9:41 PM, Robert Haas wrote:
Changing physical positioning is purely an internal matter. A
first-cut
implementation should probably just make it identical to logical
positioning, until the latter is changed by the user (after which,
physical positioning continues to reflect the original ordering).
Only
after this work has been done and gotten battle-tested, we can get
into
niceties like having the server automatically rearrange physical
positioning to improve performance.
Yeah. The problem with that is that, as Tom pointed out in a previous
iteration of this discussion, you will likely have lurking bugs. The
bugs are going to come from confusing physical vs. logical vs. column
identity, and if some of those are always-equal, it's gonna be pretty
hard to know if you have bugs that confuse the two. Now, if you could
run the regression tests with a special option that would randomly
permute the two orderings with respect to one another, that would give
you at least some degree of confidence...
Random is good, but I suspect there are some boundary cases that
could be tested too.
As for the complexity, it might make sense to only tackle part of
this at a time. There would be value in only allowing logical order
to differ from literal order, or only allowing physical order to
differ. That means you could tackle just one of those for the first
go-round and still get a benefit from it.
--
Decibel!, aka Jim C. Nasby, Database Architect [EMAIL PROTECTED]
Give your computer some brain candy! www.distributed.net Team #1828
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