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https://issues.apache.org/jira/browse/BEAM-11282?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17548950#comment-17548950
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Danny McCormick commented on BEAM-11282:
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This issue has been migrated to https://github.com/apache/beam/issues/20560
> Cannot set compression level when writing compressed files
> ----------------------------------------------------------
>
> Key: BEAM-11282
> URL: https://issues.apache.org/jira/browse/BEAM-11282
> Project: Beam
> Issue Type: Improvement
> Components: sdk-py-core
> Affects Versions: 2.25.0
> Reporter: Jack Whelpton
> Priority: P3
>
> CompressedFile._initialize_compressor hardcodes the compression level used
> when writing:
>
> self._compressor = zlib.compressobj(
> zlib.Z_DEFAULT_COMPRESSION, zlib.DEFLATED, self._gzip_mask)
>
> It would be good to be able to control this, as I have a large set of GZIP
> compressed files that are creating output 10x larger then the input size when
> writing the same data back.
>
> I've tried various monkeypatching approaches: these seem to work with the
> local runner, but failed when using DataflowRunner. For example:
>
> class WriteData(beam.PTransform):
> def __init__(self, dst):
> import zlib
> self._dst = dst
> def _initialize_compressor(self):
> self._compressor = zlib.compressobj(
> zlib.Z_BEST_COMPRESSION, zlib.DEFLATED, self._gzip_mask
> )
> CompressedFile._initialize_compressor = _initialize_compressor
> def expand(self, p):
> return p | WriteToText(
> file_path_prefix=self._dst,
> file_name_suffix=".tsv.gz",
> compression_type="gzip",
> )
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