From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] pg_upgrade may be mortally wounded |
Date: | 1999-08-01 02:06:36 |
Message-ID: | 199908010206.WAA13790@candle.pha.pa.us |
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Lists: | pgsql-hackers |
> I re-enabled pg_upgrade this afternoon, thinking that it would be easier
> to use than dump/initdb/reload for coping with the pg_statistic change
> I'm about to commit. However, testing shows that it doesn't really
> work. The "upgraded" database behaves very strangely --- vacuum tends
> to fail, and I have seen duplicate listings for attributes of a relation
> in psql's \d listing, broken links between a relation and its indices,
> and other problems.
>
> I think the problem is that pg_upgrade no longer works in the presence
> of MVCC. In particular, forcibly moving the old database's pg_log into
> the new is probably a bad idea when there is no similarity between the
> sets of committed transaction numbers. I suspect the reason for the
> strange behaviors I've seen is that after the pg_log copy, the system no
> longer believes that all of the rows in the new database's system tables
> have been committed.
>
> Is it possible to make pg_upgrade work again, perhaps by requiring a
> vacuum on the old and/or new databases just before the move happens?
> Or must we consign pg_upgrade to the dustbin of history?
I am unsure how MVCC would affect this. I will say that pg_upgrade does
not work when the underlying table structure changes, though I don't
think we have changed any of that. Strange.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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