Re: What does it mean? Plan stats and double rainbows.

On Thu, Jun 9, 2016 at 5:11 PM, Michael Moore <michaeljmoore(at)gmail(dot)com>
wrote:

> I'm having a difficult time finding documentation on EXPLAIN PLAN stats.
> For example, in
> ' -> Nested Loop Left Join (cost=0.43..1415.06 rows=2
> width=1377) (actual time=0.093..0.093 rows=0 loops=1)'
> what does 0.43..1415.06 mean? Is that a range? If so, it seems rather
> pointless, like saying "somewhere between 0 and infinity".
>
>
​Thomas' link should cover this but it isn't giving you a probabilistic
range , its giving the time to first record and time to fetch all records.
For stuff like semi-joins you don't care about the total number of records
found only that you can quickly find one record. A limited requirement but
since plan output is somewhat generic in nature it always gives both
numbers.

> Also, is there a way to tell the query planner to limit the search for the
> best plan on a per statement basis. I know that this exists as a config
> parameter but I think that applies to the entire database. I have a query
> that takes 9 times more time to plan than it does to execute.
>
>
​All parameters (in this context) are session-local in use; even if the
default value is set at the scope of the entire server. You can make them
transaction-local by using "SET LOCAL" instead of a plain "SET" when
changing them within the session.

​David J.