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

From Greg Stark
Subject Re: Patch: add timing of buffer I/O requests
Date
Msg-id CAM-w4HN2Yau2qz5GNpmG2oQvZxO+ioygjiObstXxeoeShDL=MA@mail.gmail.com
Whole thread Raw
In response to Re: Patch: add timing of buffer I/O requests  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Patch: add timing of buffer I/O requests  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Patch: add timing of buffer I/O requests  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
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.

-- 
greg


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