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Re: Ticket 117: Explain Buffers

From: Guillaume Lelarge <guillaume(at)lelarge(dot)info>
To: Magnus Hagander <magnus(at)hagander(dot)net>
Cc: pgadmin-hackers <pgadmin-hackers(at)postgresql(dot)org>
Subject: Re: Ticket 117: Explain Buffers
Date: 2010-01-25 22:46:49
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Lists: pgadmin-hackers
Le 23/01/2010 16:40, Magnus Hagander a écrit :
> 2010/1/23 Guillaume Lelarge <guillaume(at)lelarge(dot)info>:
>> Le 23/01/2010 15:14, Magnus Hagander a écrit :
>>> 2010/1/23 Guillaume Lelarge <guillaume(at)lelarge(dot)info>:
>>>> Hi,
>>>> This patch handles two new parameters for EXPLAIN: COSTS and BUFFERS.
>>>> I'm not sure that we need to add support for format. I would like to
>>>> have your opinion on this?
>>> Not really. The whole idea of using EXPLAIN on the menu is to get the
>>> graphical output, so I don't see where the user would care aobut the
>>> format of the text behind it.
>> That was also what I thought... but, if so, why do we propose VERBOSE
>> option? in this case, we don't get a graphical EXPLAIN, but a textual
> Shows how often I use it. I thought we put that stuff in the main
> explain output, not flick to text mode.
> Couldn't we put the verbose stuff in the text output and still show
> the graphical one?

Done with Euler's patch.

> Hmm. That might at least be easier to do if we use a machine format explain?
>>> That said, we might want to consider switching to using one of the
>>> machine readable formats for newer versions, and then just implement
>>> parsing of these options there. In the end, that should lead to less
>>> complicated code.. (mind you, I didn't even look at your code so I
>>> don't know how complex it is :D)
>> We can't switch completely if we want to still have compatibility with
>> the older releases. Anyways, this is something we'll have to do to ease
>> the process.
> Right. What I'd envision us doing is a simple
> if (version < 9.0)
>    run_old_explain_code();
> else
>    run_new_explain_code();
> and only the codepath for run_new_explain_code() - which would use a
> machine format output - would have the implementation of any of these
> new parameters.
> It would be slightly more work to get started since the new parser
> needs to be done (hopefully there are classes that'll do 95% of that
> for us already though), but not having to maintain manual parsing of
> these new options should be a win in the long run.
> And eventually, some 5 years from now or so, we can retire the old
> explain code because we no longer support pre-9.0 versions :D

OK. I'll add a ticket so that we can take care of this in another patch.

>>> While you're whacking around the explain code, one thing that has
>>> always nagged me, is that ANALYZE is an option for EXPLAIN. IMO we
>>> should have "Explain" and "Explain Analyze" as separate commands,
>>> because they actually do different things. And then options for things
>>> like verbose, costs, buffers etc. If we're going to change that ever,
>>> now is probably the best time :-)
>>> Thoughts?
>> I don't quite get why we should do that. You can already have an EXPLAIN
>> or an EXPLAIN ANALYZE. Or is it simply to really differentiate them?
>> because one won't launch the query and the other one will?
> Now we have:
> explain
> Explain Options -> [verbose, analyze, newstuff]
> I'd prefer
> Explain
> Explain Analyze
> Explain Options -> [verbose, newstuff]

Done. F7 launches an explain, Shift-F7 launches an explain analyze.

New patch attached.


Attachment: ticket117_v2.patch
Description: text/x-patch (8.3 KB)

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Subject: Re: Ticket 117: Explain Buffers
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