Re: Planner performance extremely affected by an hanging transaction (20-30 times)?

> As a matter of fact you get the same slow down after a rollback until
autovacuum, and if autovacuum can't keep up...

Actually, this is not what we observe. The performance goes back to the
normal level immediately after committing or aborting the transaction.

On Wed, Sep 25, 2013 at 1:30 AM, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:

> On Tue, Sep 24, 2013 at 11:03 AM, didier <did447(at)gmail(dot)com> wrote:
>
>> Hi
>>
>>
>> On Tue, Sep 24, 2013 at 5:01 PM, <jesper(at)krogh(dot)cc> wrote:
>>
>>>
>>> Apparently it is waiting for locks, cant the check be make in a
>>> "non-blocking" way, so if it ends up waiting for a lock then it just
>>> assumes non-visible and moves onto the next non-blocking?
>>>
>>
>> Not only, it's a reason but you can get the same slow down with only one
>> client and a bigger insert.
>>
>> The issue is that a btree search for one value degenerate to a linear
>> search other 1000 or more tuples.
>>
>> As a matter of fact you get the same slow down after a rollback until
>> autovacuum, and if autovacuum can't keep up...
>>
>
> Have you experimentally verified the last part? btree indices have some
> special kill-tuple code which should remove aborted tuples from the index
> the first time they are encountered, without need for a vacuum.
>
> Cheers,
>
> Jeff
>