On 23 August 2012 20:21, Bruce Momjian <bruce@momjian.us> wrote:
> On Tue, Aug 21, 2012 at 12:16:11PM +0900, Tatsuo Ishii wrote:
>> I found this in https://wiki.postgresql.org/wiki/Todo :
>>
>> Improve ability to display optimizer analysis using OPTIMIZER_DEBUG
>>
>> What does this actually mean?
>>
>> Add GUC switch to enable optimizer debug on/off?
>> More fancy/useful info should be printed?
>> If so, what kind of information is required?
>
> Well, right now, OPTIMIZER_DEBUG lets you see what plans were considered
> and removed. I was thinking that information should be available
> without a special compiled binary.
That seems like an unreasonable burden on what OPTIMIZER_DEBUG can do.
If you can't build Postgres from source, something that is relatively
low barrier, you have little hope of sensibly interpreting low-level
output from the planner. However, I could get behind having it as a
configure option, which it is currently not. It would probably also
make sense to expose SELECTIVITY_DEBUG and GEQO_DEBUG.
--
Peter Geoghegan http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training and Services