Re: performance regression in 9.2/9.3

On 09/06/14 17:30, Merlin Moncure wrote:
> On Mon, Jun 9, 2014 at 10:00 AM, Linos <info(at)linos(dot)es> wrote:
>> On 09/06/14 16:55, Merlin Moncure wrote:
>>> On Mon, Jun 9, 2014 at 9:51 AM, Linos <info(at)linos(dot)es> wrote:
>>>> Hello,
>>>>
>>>> Is this information enough? I could try to assemble a complete test case but I have very little time right now because I am trying to meet a very difficult deadline.
>>>>
>>>> I will do ASAP if needed.
>>> It is not -- it was enough to diagnose a potential problem but not the
>>> solution. Tom was pretty clear: "I'd like to see a self-contained
>>> test case, by which I mean full details about the table/view schemas;
>>> it's not clear whether the actual data is very important here.".
>>>
>>> merlin
>> Merlin, in the email I replied to are attached the table/view schemas, I was referring to this information as enough or not. Tom said "full details about the table/view schemas" and these details are attached to the original email I replied to.
> A self contained test case would generally imply a precise sequence of
> steps (possibly with supplied data, or some manipulations via
> generate_series) that would reproduce the issue locally. Since data
> may not be required, you might be able to get away with a 'schema only
> dump', but you'd need to make sure to include necessary statistics
> (mostly what you'd need is in pg_statistic which you'd have to join
> against pg_class, pg_attribute and pg_namespace).
>
> Ideally, you'd be able to restore your schema only dump on a blank
> database with autovacuum disabled, hack in your statistics, and verify
> your query produced the same plan. Then (and only then) you could tar
> up your schema only file, the statistics data, and the query to update
> the data, and your query with the bad plan which you've triple checked
> matched your problem condition's plan, and send it to Tom. There
> might be some things I've missed but getting a blank database to
> reproduce your problem with a minimum number of steps is key.
>
> merlin

oh I understand now, sorry for the misunderstanding, I will prepare the complete test case ASAP, thank you for the explanation Merlin.

Miguel Angel.