Re: storage of sensor data with Fourier transforms - Mailing list pgsql-hackers

From Nathan Buchanan
Subject Re: storage of sensor data with Fourier transforms
Date
Msg-id d51c18ed0705052307w38b1cf65j1f2f625eec797904@mail.gmail.com
Whole thread Raw
In response to Re: storage of sensor data with Fourier transforms  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers


On 5/5/07, Tom Lane <tgl@sss.pgh.pa.us> wrote:
"Nathan Buchanan" <nbinont@gmail.com> writes:
> I had the idea of taking the Fourier transform of the waveform and storing
> the waveform internally that way to reduce storage requirements.

Aside from what Steve said: The Fourier transform in itself doesn't
reduce data size --- it's N points in, N points out.  If you want to
reduce storage requirements you have to resort to lossy compression, ie,
deliberately throwing away some data.  The transformed data might be
more suitable for doing that (eg you can selectively discard
high-frequency components) but do you really want to?  Usually the point
of storing measurements is so you can do unspecified analysis on them
later.  Applying lossy compression will restrict what you can
(meaningfully) do later on.

                        regards, tom lane

Thanks for the replies. It seems I need to examine my plan more closely.

Nathan

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