Datachain

TarVFile

TarVFile

Bases: VFile

Virtual file model for files extracted from tar archives.

open classmethod 

open(file: File, location: list[dict], block_size: int | None = None)

Stream file from tar archive based on location in archive.

Reads always consult the cache (hit → local, miss → remote stream); _caching_enabled only governs whether a miss is also persisted.

Source code in datachain/lib/file.py 
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
@classmethod
def open(cls, file: "File", location: list[dict], block_size: int | None = None):
    """Stream file from tar archive based on location in archive.

    Reads always consult the cache (hit → local, miss → remote stream);
    ``_caching_enabled`` only governs whether a miss is also persisted.
    """
    tar_file = cls.parent(file, location)

    loc = location[0]

    if (offset := loc.get("offset", None)) is None:
        raise VFileError("'offset' is not specified", file.source, file.path)

    if (size := loc.get("size", None)) is None:
        raise VFileError("'size' is not specified", file.source, file.path)

    client = file._catalog.get_client(tar_file.source)
    fd = client.open_object(tar_file, use_cache=True, block_size=block_size)
    return FileSlice(fd, offset, size, file.name)