Robert Haas escribió:
> After some thought, it seems pretty clear, at least to me, that the
> third (hypothetical) command should not change the result of "SELECT *
> FROM tricky" (the contrary conclusion gives rise to a lot of problems,
> especially if there are other views depending on it). But what will
> "pg_dump -t tricky" output at this point? I suspect it will be
> necessary to introduce some new syntax here.
Everything that's user-visible needs to use logical positioning. That
includes pg_dump.
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.
Column identity is, of course, set in stone as soon as decided for the
first time.
--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.