On 4/14/16 6:16 AM, Andreas Karlsson wrote:
On 04/14/2016 12:22 PM, Craig Ringer wrote:
I'd find a pg_get_tabledef(...) built-in function more interesting for
this particular purpose than pg_dump as a library would be. We already
have pg_get_viewdef(...), pg_get_functiondef(...) etc.


I am personally not a fan of the pg_get_Xdef() functions due to their
heavy reliance on the syscache which feels rather unsafe in combination
with concurrent DDL. I would not be surprised if we have some low
probability bugs which cause inconsistent backups there which just has
not hit enough people yet to have been reported. And this problem will
only get worse as we reduce the lock level of more DDL.

The other issue specific to pg_dump is it often needs to do something different than what pg_get_*def would do to support version upgrades.

I agree that it would be nice to have better DDL generation capabilities in the database, but I think the right way to do that is to create the pg_dump library and then wrap that as a (version-specific) extension. That way you could loan the pg_dump-9.5 extension in a 9.3 database if you wanted.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com


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