On Sat, Dec 12, 2015 at 06:48:58PM +0800, Craig Ringer wrote:
> Being able to access pg_dump and pg_restore's dependency resolution logic,
> object dumping routines, etc from regular SQL and from the SPI would be
> wonderful.
As I understand it, pushing these into a library has been proposed but
not rejected. That it hasn't happened yet is mostly about the lack of
tuits (the round ones) to rewrite the functionality as libraries and
refactor pg_dump/pg_restore to use only calls to same. As usual, it's
less about writing the code and more about the enormous amount of
testing any such a refactor would entail.
> I believe the main complaints about doing that when it was discussed in the
> past were issues with downgrading. A pg_get_tabledef(...) in 9.6 might emit
> keywords etc that a 9.2 server wouldn't understand, and the way we
> currently solve this is to require that you run 9.2's pg_dump against the
> 9.6 server to get a 9.2-compatible dump. So if we had pg_get_blahdef
> functions we'd still need external versions, so why bother having them?
You have made a persuasive case that major version downgrading is not
a problem we need to solve on the first go.
> The alternative is to have all the get_blahdef functions accept a param for
> server version compatibility, which would work but burden future servers
> with knowledge about older versions' features and corresponding code cruft
> for some extended period of time.
>
> So it's gone nowhere to date.
I believe that refactoring much of pg_dump's functionality for the
current version of the server into SQL-accessible functions and making
pg_dump use only those functions is achievable with available
resources.
Such a refactor need not be all-or-nothing. For example, the
dependency resolution stuff is a first step that appears to be worth
doing by itself even if the effort then pauses, possibly for some
time.
Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
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