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Re: Need advice for migration to pgsql



In message <87g1sejp03.fsf@baal.winnegan.north.de>, writes:
  >Before uploading a pgsql_v6.1.1 package, I need some advice how to
  >cope with a migration problem for users who have valuable data in a
  >previous postgres95 installation.
...
  >Since pgsql replaces files from postgres95, the backup has to be run
  >before pgsql is unpacked or postgres95 is removed.
  >
  >I'm thinking of a postgres95-migrate package where pgsql predepends
  >upon. Its postinst will check for postgres95 being installed and only
  >when this test succeeds prompt the user whether existing databases are
  >to be dumped. The postinst will only succeed when postgres95 is not
  >installed or existing databases have been successfully dumped.
 
I think this is very important.  You should also consider the position of
those who have mixed case table and field names, which are no longer
supported by 6.1 (for SQL compatibility), and also the case of people
who might have a non-debianised version occupying the same filespace as
the new debian package.  I don't think that any part of the conversion
procedure should be automatic; at the least you should explain what is
going to happen to any existing files, whether in a package or not, and
wait for the installer to give explicit consent.

Even with that consent, I think that the existing database and programs should 
be moved rather than deleted.  Otherwise there is too much risk of a
disaster.  Your postgres95-migrate package should provide separate
programs for renaming/moving the old software and data and for deleting it.
The deletion should only happen when the operation of the new software
and the data conversion have been verified.

-- 
Oliver Elphick                                Oliver.Elphick@lfix.co.uk
Isle of Wight                                  http://lfix.co.uk/oliver

     Make it idiot-proof, and someone will breed a better idiot.



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