Unable to open dataset that was created with Blosc(2) compression

[Leonard-Mueller]

Hi, I created a dataset with the following python code

    compression_options = hdf5plugin.Blosc2(
        cname='blosclz',  # Blosc2 supports 'zstd', 'lz4', 'blosclz', etc.
        clevel=9,  # Compression level (1-9)
        filters=hdf5plugin.Blosc2.SHUFFLE,  # Better for floating point data
    )

    if isinstance(da_arr.data, da.Array):
        chunks = da_arr.data.chunksize
        is_dask = True
    else:
        chunks = None
        is_dask = False
    dset = f.create_dataset(
        dset_name,
        shape=da_arr.shape,  # Keep original shape
        dtype=da_arr.dtype,  # Ensure proper data type
        chunks=chunks,  # copy chunksize of underlying dask array
        compression = compression_options
    )

The h5web (in vscode) viewer gives this error:

HDF5-DIAG: Error detected in HDF5 (1.14.2) thread 0:
  #000: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5D.c line 1061 in H5Dread(): can't synchronously read data
    major: Dataset
    minor: Read failed
  #001: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5D.c line 1008 in H5D__read_api_common(): can't read data
    major: Dataset
    minor: Read failed
  #002: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 2092 in H5VL_dataset_read_direct(): dataset read failed
    major: Virtual Object Layer
    minor: Read failed
  #003: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLcallback.c line 2048 in H5VL__dataset_read(): dataset read failed
    major: Virtual Object Layer
    minor: Read failed
  #004: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5VLnative_dataset.c line 363 in H5VL__native_dataset_read(): can't read data
    major: Dataset
    minor: Read failed
  #005: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Dio.c line 279 in H5D__read(): can't initialize I/O info
    major: Dataset
    minor: Unable to initialize object
  #006: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Dchunk.c line 1088 in H5D__chunk_io_init(): unable to create file and memory chunk selections
    major: Dataset
    minor: Unable to initialize object
  #007: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Dchunk.c line 1231 in H5D__chunk_io_init_selections(): unable to create file chunk selections
    major: Dataset
    minor: Unable to initialize object
  #008: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5Dchunk.c line 1692 in H5D__create_piece_file_map_all(): can't insert chunk into skip list
    major: Dataspace
    minor: Unable to insert object
  #009: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5SL.c line 1036 in H5SL_insert(): can't create new skip list node
    major: Skip Lists
    minor: Unable to insert object
  #010: /__w/libhdf5-wasm/libhdf5-wasm/build/1.14.2/_deps/hdf5-src/src/H5SL.c line 709 in H5SL__insert_common(): can't insert duplicate key
    major: Skip Lists
    minor: Unable to insert object

This is the metadata displayed with h5web of the dataset:

  "name": "slope_map",
  "path": "/slope_map",
  "attributes": [
    {
      "name": "DIMENSION_LIST",
      "shape": [
        2
      ],
      "type": {
        "class": "Array (variable length)",
        "base": {
          "class": "Reference"
        }
      }
    }
  ],
  "kind": "dataset",
  "shape": [
    12000,
    12001
  ],
  "type": {
    "class": "Float",
    "endianness": "little-endian",
    "size": 32
  },
  "chunks": [
    1000,
    1000
  ],
  "filters": [
    {
      "id": 32026,
      "name": "blosc2",
      "cd_values": [
        1,
        0,
        4,
        4000000,
        9,
        1,
        0,
        2,
        1000,
        1000
      ]
    }
  ],
  "rawType": {
    "signed": false,
    "type": 1,
    "vlen": false,
    "littleEndian": true,
    "size": 4,
    "total_size": 144012000
  }
}

With for instance gzip compression it works just fine. I am also read the dataset again with the h5py library. Should h5web be able to read blosc and blosc2 compressed datasets out of the box?

[axelboc]

Hi @Leonard-Mueller, the VSCode extension supports Blosc2 compression out of the box:

import h5py
import numpy
import hdf5plugin

with h5py.File('blosc2.h5', 'w') as file:
  file.create_dataset(
    'blosc2',
    data=numpy.arange(100),
    compression=hdf5plugin.Blosc2(
      cname='blosclz',
      clevel=9,
      filters=hdf5plugin.Blosc2.SHUFFLE
    )
  )

blosc2.zip

So I don't think the problem comes from the compression per se. Perhaps your dataset is somehow malformed and the Blosc2 filter is less lenient to it than the gzip filter?