Andres Freund wrote:
> On 2014-03-17 21:09:10 +0000, Greg Stark wrote:
> > That said, it would be nice to actually fix the problem, not just
> > detect it. Eventually vacuum would fix the problem. I think. I'm not
> > really sure what will happen actually.
> Indexes will quite possibly stay corrupted. I think. If there was a
> index lookup for a affected row, the kill_prior_tuple logic will have
> quite possibly have zapped the index entry.
> Aside from that, it looks like VACUUM will have a hard time cleaning up
> as well. It looks to me like heap_prune_chain() won't remove tuples that
> are marked as both HeapTupleHeaderIsHeapOnly() and
> HeapTupleHeaderIsHotUpdated(), i.e. intermediate tuples in a HOT
> chain. Neither will lazy_scan_heap()...

Ugh :-(

> I think the best way to really cleanup a table is to use something like:
> where text is the previous type of the column. That should trigger a
> full table rewrite, without any finesse about tracking ctid chains.

Isn't this what VACUUM FULL does?

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Training & Services

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