Re: Patch: add timing of buffer I/O requests - Mailing list pgsql-hackers

From Robert Haas
Subject Re: Patch: add timing of buffer I/O requests
Date
Msg-id CA+TgmobXoDG-T5BoTy3fxb4SG2uyohy+87bw2AgjaTfrm84nOQ@mail.gmail.com
Whole thread Raw
In response to Re: Patch: add timing of buffer I/O requests  (Greg Stark <stark@mit.edu>)
List pgsql-hackers
On Wed, Apr 25, 2012 at 1:58 PM, Greg Stark <stark@mit.edu> wrote:
> On Wed, Apr 25, 2012 at 5:47 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Also, as was pointed out upthread, the underlying data in shared memory
>> is almost certainly never going to be infinite-precision; so using
>> numeric in the API seems to me to be more likely to convey a false
>> impression of exactness than to do anything useful.
>
> I don't think that follows. The underlyng data will be measured in
> some metric unit of time like microsecond or nanosecond or something
> like that. So a base-10 representation will show exactly the precision
> that the underlying data has. On the other hand a floating point
> number will show a base-2 approximation that may in fact display with
> more digits than the underlying data representation has.

I wholeheartedly agree.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company


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