Re: EXPLAIN and nfiltered

On 2010-11-18 6:26 PM +0200, Tom Lane wrote:
> Marko Tiikkaja<marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> writes:
>> Here's a patch for showing in EXPLAIN ANALYZE the number of rows a plan
>> qual filtered from a node's input.
>
> I don't like this a whole lot. It's unclear what "filtered" means,
> or why it's worth expending precious EXPLAIN ANALYZE output space for.

The name can be changed, of course. But I think the idea is good; I
find myself constantly manually finding out how many rows were actually
filtered.

> Also, you've not implemented it for any except scan nodes;

That was intentional.

> and I
> think it's not going to be entirely well-defined for join nodes,
> since it's somewhat arbitrary which conditions are considered part
> of the join qual versus the filter. (That problem will get worse
> not better with the planned generalization of inner indexscans,
> since there may be join quals in scan nodes.)

Hmm.. Maybe I'm misunderstanding something, but I don't see that as a
huge problem.

Regards,
Marko Tiikkaja