Re: INSERT...ON DUPLICATE KEY LOCK FOR UPDATE

On Sat, Jan 18, 2014 at 5:28 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> I was wondering if that might cause deadlocks if an existing index is
>> changed from unique to non-unique, or vice versa, as the ordering would
>> change. But we don't have a DDL command to change that, so the question is
>> moot.
>
> It's not hard to imagine someone wanting to add such a DDL command.

Perhaps, but the burden of solving that problem ought to rest with
whoever eventually propose the command. Certainly, if someone did so
today, I would object on the grounds that their patch precluded us
from ever prioritizing unique indexes, to get them out of the way
during insertion, so I am not actually making such an effort more
difficult than it already is. Moreover, avoiding entirely predictable
index bloat is more important than making supporting this yet to be
proposed feature's implementation easier. I was surprised when I
learned that things didn't already work this way.

Attached patch, broken off from my patch has relcache sort indexes by
(!indisunique, relindexid).

--
Peter Geoghegan