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Do not try to compress variable-sized varaibles #1424

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Merged
lesserwhirls merged 1 commit into from
Mar 10, 2025
Merged

Do not try to compress variable-sized varaibles #1424

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17 changes: 16 additions & 1 deletion cdm/core/src/main/java/ucar/nc2/write/Nc4ChunkingStrategy.java
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,9 @@

package ucar.nc2.write;

import ucar.ma2.DataType;
import ucar.nc2.Attribute;
import ucar.nc2.Structure;
import ucar.nc2.Variable;
import ucar.nc2.constants.CDM;
import javax.annotation.concurrent.Immutable;
Expand Down Expand Up @@ -52,7 +54,20 @@ protected Nc4ChunkingStrategy(int deflateLevel, boolean shuffle) {

@Override
public int getDeflateLevel(Variable v) {
return deflateLevel;
return isCompressible(v) ? deflateLevel : 0;
}

// compression should not be applied to variable-sized variables
// see Unidata/netcdf-java#1420
private boolean isCompressible(Variable v) {
if (v.getDataType().equals(DataType.STRING) || v.isVariableLength())
return false;

if (v.getDataType().equals(DataType.STRUCTURE)) {
Structure s = (Structure) v;
return s.getVariables().stream().allMatch(this::isCompressible);
}
return true;
}

@Override
Expand Down