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[netCDF #PJC-712062]: nccopy cannot copy a nc3 file to a nc4 file

Hi Kent,

It is a concern, certainly, that our users may use an attribute/name pair
CLASS/IMAGE, and be confused about why it doesn't work.  Ideally we'd be
able to set an error code indicating that a reserved keyword was used.
Since it doesn't look like that's the case, documenting this will probably
be sufficient, especially without anybody else having encountered/reported
this issue.

We could always implement our own list of reserved keywords in nccopy/ncgen
for various file types and throw a warning there, I suppose.  It wouldn't
be hard, but it is also relatively low priority for the moment.

-Ward


On Thu, Jan 14, 2016 at 3:03 PM, Kent Yang <address@hidden>
wrote:

> New Client Reply: nccopy cannot copy a nc3 file to a nc4 file
>
> Hi Ward,
>
> Thanks for looking into this quickly.
> I just checked the latest HDF5 trunk version. H5DSattach_scale only
> returns FAIL if anything goes wrong and there is one line coding as
> /*check if the dataset is a "reserved" dataset(image,table)*/,
> If yes, return FAIL.
>
> Any thoughts on what you expect the DSattach_scale to retun?
> Are you concerned that the some NetCDF users may use the attribute CLASS
> and assign a name IMAGE; the DS restriction may avoid them creating a valid
> file?
>
> Kent
>
> -----Original Message-----
> From: Unidata netCDF Support [mailto:address@hidden]
> Sent: Thursday, January 14, 2016 3:11 PM
> To: Kent Yang
> Cc: address@hidden
> Subject: [netCDF #PJC-712062]: nccopy cannot copy a nc3 file to a nc4 file
>
> Hi Kent,
>
> Thanks for the additional information; we'll have to discuss how to handle
> this internally, since we'll definitely want to handle this but we also
> don't want to modify an end-user data set programatically.  Do you know
> offhand if H5DSattach_scale sets/returns any sort of error code or throws a
> signal we can catch, in addition to returning FAIL?
>
> -Ward
>
> address@hidden>
> wrote:
>
> > New Client Reply: nccopy cannot copy a nc3 file to a nc4 file
> >
> > I did a little more investigation of the original HDF5 that may be
> helpful.
> > In the original nc3 file, the attribute CLASS=IMAGE. This is a special
> > convention for an HDF5 high-level image file.
> > I think nccopy fails when calling H5DSattach_scale. In the function
> > H5DSattach_scale, it will return FAIL if this dataset is an
> > image(CLASS=IMAGE) or table(CLASS = TABLE).
> > HDF5 IMAGE and TABLE cannot have dimension scales.
> >
> > One solution for this problem is to check if the attribute CLASS is
> > IMAGE or TABLE, don't attach the scale if finding the variable is
> > actually HDF5 image or table.
> >
> > Hope it helps,
> >
> > Kent
> > -----Original Message-----
> > From: Unidata netCDF Support [mailto:address@hidden]
> > Sent: Wednesday, January 13, 2016 3:10 PM
> > To: Kent Yang
> > Cc: address@hidden
> > Subject: [netCDF #PJC-712062]: nccopy cannot copy a nc3 file to a nc4
> > file
> >
> > I have recreated the error using cygwin.
> >
> > A couple of things I noticed so far:
> > 1. It appears to actually create the output netcdf4 file.
> > 2. A diff of the metadata appears to show that the netcdf3 metadata
> >    and the netcdf4 metadata are consistent except that the netcdf4
> >    metadata is missing all attributes named 'CLASS' or 'NAME'.
> >    Weird.
> >
> > =Dennis Heimbigner
> >   Unidata
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: PJC-712062
> > Department: Support netCDF
> > Priority: Normal
> > Status: Closed
> >
> >
> >
> > Ticket Details
> > ===================
> > Ticket ID: PJC-712062
> > Department: Support netCDF
> > Priority: Normal
> > Status: Open
> > Link:
> > https://andy.unidata.ucar.edu/esupport/staff/index.php?_m=tickets&_a=v
> > iewticket&ticketid=26542
> >
> >
>
>
>
> Ticket Details
> ===================
> Ticket ID: PJC-712062
> Department: Support netCDF
> Priority: Normal
> Status: Open
>
>
>
> Ticket Details
> ===================
> Ticket ID: PJC-712062
> Department: Support netCDF
> Priority: Normal
> Status: Open
> Link:
> https://andy.unidata.ucar.edu/esupport/staff/index.php?_m=tickets&_a=viewticket&ticketid=26542
>
>



Ticket Details
===================
Ticket ID: PJC-712062
Department: Support netCDF
Priority: Normal
Status: Open