Re: EXPLAIN BUFFERS - Mailing list pgsql-hackers

From Robert Haas
Subject Re: EXPLAIN BUFFERS
Date
Msg-id 603c8f070912100749g1436cfa3n218abffb231a41ba@mail.gmail.com
Whole thread Raw
In response to Re: EXPLAIN BUFFERS  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: EXPLAIN BUFFERS  (Greg Smith <greg@2ndquadrant.com>)
List pgsql-hackers
On Thu, Dec 10, 2009 at 10:44 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alvaro Herrera <alvherre@commandprompt.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


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