Re: Re: [GENERAL] contrib/plantuner - enable PostgreSQL planner hints

Robert Haas <robertmhaas(at)gmail(dot)com> wrote:

> I sometimes want to know what the planner thinks the cost of some
> plan other than the one actually selected would be.

Another DBMS I used for years had a way to turn on an *extremely*
verbose mode for their planner; it showed everything it considered
with its related cost information. Even a moderately complex query
generated hundreds or thousands of lines of output, so I rarely used
it; but for those particularly stubborn queries, where you just can't
understand why it's picking the plan it is, a little work wading
through the output would *always* clear up the mystery.

Now that we can generate EXPLAIN output in more structured formats,
perhaps we could think about adding an "extremely verbose" mode where
the planner would "think out loud" as a whole separate section from
where we show the chosen plan?

-Kevin