On 03/02/2015 09:29 PM, Peter Geoghegan wrote:
> On Mon, Mar 2, 2015 at 11:20 AM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
>> Are we OK with a 10% overhead, caused by the locking? That's probably
>> acceptable if that's what it takes to get UPSERT. But it's not OK just to
>> solve the deadlock issue with regular insertions into a table with exclusion
>> constraints. Can we find a scheme to eliminate that overhead?
>
> Looks like you tested a B-Tree index here. That doesn't seem
> particularly representative of what you'd see with exclusion
> constraints.
Hmm. I used a b-tree to estimate the effect that the locking would have
in the UPSERT case, for UPSERT into a table with a b-tree index. But
you're right that for the question of whether this is acceptable for the
case of regular insert into a table with exclusion constraints, other
indexams are more interesting. In a very quick test, the overhead with a
single GiST index seems to be about 5%. IMHO that's still a noticeable
slowdown, so let's try to find a way to eliminate it.
- Heikki