Re: Speaking of upgrades... (was Re: Predicted ...)

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On 01/27/07 00:19, Martijn van Oosterhout wrote:
> On Fri, Jan 26, 2007 at 10:16:39PM -0600, Ron Johnson wrote:
>> What are your plans for reducing the number of resources needed to
>> upgrade databases?
>
> As noted, the table structure changes only slightly between versions,
> if at all. What does change significantly is the catalog. Even now
> there have been significant underlying changes to make the catalog
> totally incompatable. There has been work on a pg_upgrade tool which
> would create a new database with the new version and then copy the data
> tables from the old version and rebuild the indexes. The idea being
> that the data is large, but the underlying system is fairly small.

You mean "copy just the system catalog"?

> In theory it could work, but I don't know about the status. There has
> been some support from the core that *if* such a pg_upgrade tool
> existed, *then* they would provide some backward compatability for he
> datatypes.

That's how the system I use at work does upgrades. The existing
user data formats don't change, but the system catalog does. So,
when you convert a DB, it makes a fresh copy of the catalog, and
then migrates the old catalog to the new catalog. 15 year old
systems can be upgraded that way, with no harm to the user data.
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