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Default to ZSTD compression when writing Parquet #981

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Default to ZSTD compression when writing Parquet #981

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18 changes: 13 additions & 5 deletions python/datafusion/dataframe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -620,16 +620,24 @@ def write_csv(self, path: str | pathlib.Path, with_header: bool = False) -> None
def write_parquet(
self,
path: str | pathlib.Path,
compression: str = "uncompressed",
compression: str = "ZSTD",
compression_level: int | None = None,
) -> None:
"""Execute the :py:class:`DataFrame` and write the results to a Parquet file.

Args:
path: Path of the Parquet file to write.
compression: Compression type to use.
compression_level: Compression level to use.
"""
path (str | pathlib.Path): The file path to write the Parquet file.
compression (str): The compression algorithm to use. Default is "ZSTD".
compression_level (int | None): The compression level to use. For ZSTD, the
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We should document that the compression level is different per algorithm. It's only zstd that has a 1-22 range IIRC.

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Do you mean like

compression_level (int | None): The compression level to use. For ZSTD, the
            recommended range is 1 to 22, with the default being 3. Higher levels
            provide better compression but slower speed.

recommended range is 1 to 22, with the default being 3. Higher levels
provide better compression but slower speed.
"""
# default compression level to 3 for ZSTD
if compression == "ZSTD":
if compression_level is None:
compression_level = 3
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3 seems like an awfully low compression default. We should evaluate what other libraries use as the default compression setting.

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It might be nice to dig into what DuckDB's defaults are: https://duckdb.org/docs/data/parquet/overview.html#writing-to-parquet-files

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@kosiew kosiew Dec 27, 2024 •
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3 seems like an awfully low compression default. We should evaluate what other libraries use as the default compression setting.

I used the default compression level in the manual from Facebook (author of zstd) - https://facebook.github.io/zstd/zstd_manual.html

I could not find a default in DuckDB's documentation.

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hi @kylebarron ,

Shall we adopt delta-rs' default, and use 4 as the default ZSTD compression level?

elif not (1 <= compression_level <= 22):
raise ValueError("Compression level for ZSTD must be between 1 and 22")
self.df.write_parquet(str(path), compression, compression_level)

def write_json(self, path: str | pathlib.Path) -> None:
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