As of now, explain.depesz.com will provide hints for seq scans with multiple equality conditions joined with AND.
For example:
SELECT * FROM TABLE WHERE proj_type = 'GR14' AND week = 2000 AND pop_flag = '1'
You can see it in action in this plan.
Hope you'll find it useful.
I just pushed change to explain.depesz.com that allows for processing and displaying hints for plans.
For example, take a look at this plan, and check if you'll notice subtle “HINTS" tab.
In there you will see example hints – one about sort and memory, and the other about missing index.
It is not much, but it's a step in (hopefully) right direction, when the explain tool will also provide, automatically, some ideas on what to do to make the thing faster.
Hope you'll find it useful.
On 18th of July, Tom Lane committed patch:
Add GET STACKED DIAGNOSTICS plpgsql command to retrieve exception info. This is more SQL-spec-compliant, more easily extensible, and better performing than the old method of inventing special variables. Pavel Stehule, reviewed by Shigeru Hanada and David Wheeler
Continue reading Waiting for 9.2 – Stacked Diagnostics in PL/pgSQL