Re: verbose cost estimate

On Mon, Dec 09, 2019 at 05:40:40PM -0500, Tom Lane wrote:
>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> ... Perhaps a path-specific struct, referenced
>> from the path and built only with verbose explain would be fine?
>
>How would that work, given that the planner doesn't know whether its
>output is going to get explained?  With features like the plan cache
>and auto_explain in mind, it's very hard to see how you avoid having
>to save the information always.
>

I don't know, but my assumption is that this information would be needed
only very rarely. So maybe we could pass a flag enabling this to the
planner when executed from explain, and disable storing the plan in the
plan cache, or something. And the additional info would be only
available when explicitly requested using an extra EXPLAIN option.

So for example auto_explain would not really show this (or it might get
an extra option, with additional overhead).

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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