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Re: [Gnumed-devel] Approaches to maintain clinical data uptime

From: Karsten Hilbert
Subject: Re: [Gnumed-devel] Approaches to maintain clinical data uptime
Date: Sun, 30 Apr 2006 12:42:39 +0200
User-agent: Mutt/1.5.11+cvs20060403

On Sun, Apr 30, 2006 at 12:05:33PM +0200, Karsten Hilbert wrote:

> I have written a partial update-v2-v3.sql script and let me
> tell you it *can* get quite complex. Simple alter statements
> won't suffice since we do have to deal with data already in
> the tables.
For the record, our update-db concept is as follows such
that it is entirely non-destructive:

Suppose update from v2 to v3.

- clients are disconnected
- database "gnumed_v3" is created with template "gnumed_v2"
- now we have an exact copy of gnumed_v2 in gnumed_v3, warts and all
- the update ddl (alter etc) is run against "gnumed_v3"
- if all goes well the gnumed_v3 now really actually contains a v3 schema
- clients connect to "gnumed_v3"

If anything breaks in updating the database clients connect
to "gnumed_v2" again and the whole procedure is back to
square one. If anyone can come up with a more secure
procedure I'd like to hear about it.

Note that this isn't just a plan. It's working reality
(apart from the fact that due to lacking demand - no v1
users out there to my knowledge - we don't actually have a
complete update-ddl-v1-v2.sql script - but we could if
demand is there).

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