Re: Migration from 7.1.3. to 7.4.7.

smarlowe@g2switchworks.com (Scott Marlowe) writes:
> On Wed, 2005-03-16 at 06:07, Dr. Roger Wießner wrote:
>> Can anyone tell me how to successfully migrate from 7.1.3. to 7.4.7.? I get
>> lots of errors...
>
> Try to have both installed at once (separate dirs, or separate machines)
> and dump the 7.1.3 db with the 7.4.7 pg_dump.  You might want to do a
> file system backup and an upgrade of 7.1.3 to the last version of 7.1.3.
>
> On rare occasions, an intermediate upgrade to something in between may
> help, but I've not used 7.1 in a VERY long time.

7.1 is _mighty_ old, which gives a pretty considerable chance of there
being data type changes that may break.

I seem to recall doing an upgrade of some databases to 7.2 and
discovering that the date type being used in the "ancient" version
(which might well have been 6.5 or 7.0, even older than 7.1!) not
existing in more modern versions.

We wound up splitting the conversion into two pieces:

 - A schema conversion, where the types of fields were updated to
   those available in more modern versions.  This is where most of
   the fiddling took place.

 - A data copy, where (if memory serves) we dumped the data as a set of
   INSERT statements rather than via COPY 'dumps'.

   Careful addition of BEGIN/COMMIT allowed the load to be acceptably
   fast, and the use of INSERT avoided differences between COPY
   formats...

I'd do some "dry runs" (where you don't expect the results to
necessarily be useful) to see what problems fall out.
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