| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Takahiro Itagaki <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> |
| Cc: | Euler Taveira de Oliveira <euler(at)timbira(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: EXPLAIN BUFFERS |
| Date: | 2009-12-14 04:13:11 |
| Message-ID: | 603c8f070912132013r2142226ao19f00c75d5e9ef29@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Sun, Dec 13, 2009 at 10:00 PM, Takahiro Itagaki
<itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> wrote:
>> Two other thoughts:
>>
>> 1. It doesn't appear that there is any provision to ever zero
>> pgBufferUsage. Shouldn't we do this, say, once per explain, just to
>> avoid the possibility of overflowing the counters?
>
> I think the overflowing will not be a problem because we only use
> the differences of values. The delta is always corrent unless we use
> 2^32 buffer accesses during one execution of a node.
Hmm... you might be right. I'm not savvy enough to know whether there
are any portability concerns here.
Anyone else know?
...Robert
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