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[netCDF #VGE-187371]: deflating scalar

> We have netcdf data files that were written with netcdf-4.0.  In these files 
> the deflate and deflate_level are set to 0 for scalars.  With netcdf-4.1.1 
> this no longer works.  In nc4var.c  the function nc_def_var_extra returns 
> NC_EINVAL  because of the check:
> if (!var->ndims)
> Code that was written to handle the netcdf files produced by netcdf-4.0 
> worked because this check wasn't made back then.  When I recompile linking to 
> netcdf-4.1.1 the code doesn't work anymore.
> Is this behavior on purpose?  The variable's chunking is set to NC_CONTIGUOUS 
> and deflate is set to 0.  Historically that combo was sufficient.
> Will

Howdy Will!

This has been fixed in the netCDF daily snapshot. You can get the snapshot, 
wait for the next release (before the end of the year), or change your copy of 
the code to return NC_NOERR.

This was done on purpose, because there can be no compression of a scalar in 

But someone suggested that I was being to strict, and that I should just ignore 
attempts to deflate scalars. I'm OK with that, but when you check the 
properties of the file, netcdf will still tell you that there is no compression 
on that variable. (Because there isn't, really).

Also in the snapshot, netCDF will now ignore attempts to set deflation to zero. 
This causes everything to be run through the gzip compression filter, but no 
compression is done. It causes bad performance and does nothing to the data, so 
now it is simply ignored.



Ticket Details
Ticket ID: VGE-187371
Department: Support netCDF
Priority: Normal
Status: Closed

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