Re: EXPLAIN BUFFERS

On Thu, Dec 10, 2009 at 10:44 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
>> Takahiro Itagaki escribió:
>>> Blocks: (shared hit=96 read=1544 written=0) (local hit=0 read=0 written=0) (temp read=0 written=0)
>
>> Maybe I missed part of this discussion, but it seems a bit weird to have
>> an option named "buffers" turn on a line that specifies numbers of
>> "blocks".
>
> Agreed, and I have to agree also with the people who have been
> criticizing the output format.  If we were trying to put the block
> counts onto the same line as everything else then maybe parentheses
> would be helpful, but here they're just clutter.
>
> Perhaps
>
>        I/O: shared hit=96 read=1544 written=0 local hit=0 read=0 written=0 temp read=0 written=0
>
> (although this would suggest making the option name "io" which is
> probably a poor choice)
>
> I also suggest that dropping out zeroes might help --- a large fraction
> of EXPLAIN work is done with SELECTs that aren't ever going to write
> anything.  Then the above becomes
>
>        I/O: shared hit=96 read=1544
>
> which is vastly more readable.  You wouldn't want that to happen in
> machine-readable formats of course, but I think we no longer care about
> whether the text format is easy for programs to parse.

Oooh, that's a nice idea, though I think you should throw in some
commas if there is, say, both shared and local stuff:

shared hit=96 read=1544, local read=19

I don't think IO is a terrible name for an option but I like BUFFERS
better. I don't think the BUFFERS/BLOCKS confusion is too bad, but
perhaps we could use BUFFERS in both places.

...Robert