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ARROW-1276: enable parquet serialization of empty DataFrames #906

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crepererum wants to merge 2 commits into from
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ARROW-1276: enable parquet serialization of empty DataFrames #906

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1d9cc41
add missing conda packages to python dev. doc
crepererum Jul 28, 2017
1c1c92c
ARROW-1276: enable parquet serialization of empty DataFrames
crepererum Jul 28, 2017
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2 changes: 1 addition & 1 deletion python/doc/source/development.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -84,7 +84,7 @@ from conda-forge:
conda create -y -q -n pyarrow-dev \
python=3.6 numpy six setuptools cython pandas pytest \
cmake flatbuffers rapidjson boost-cpp thrift-cpp snappy zlib \
brotli jemalloc -c conda-forge
brotli jemalloc lz4-c zstd -c conda-forge
source activate pyarrow-dev


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5 changes: 4 additions & 1 deletion python/pyarrow/_parquet.pyx
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Expand Up @@ -629,7 +629,10 @@ cdef class ParquetWriter:
cdef CTable* ctable = table.table

if row_group_size is None or row_group_size == -1:
row_group_size = ctable.num_rows()
if ctable.num_rows() > 0:
row_group_size = ctable.num_rows()
else:
row_group_size = 1
elif row_group_size == 0:
raise ValueError('Row group size cannot be 0')

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12 changes: 12 additions & 0 deletions python/pyarrow/tests/test_parquet.py
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Expand Up @@ -265,6 +265,18 @@ def test_read_pandas_column_subset(tmpdir):
tm.assert_frame_equal(df[['strings', 'uint8']], df_read)


@parquet
def test_pandas_parquet_empty_roundtrip(tmpdir):
df = _test_dataframe(0)
arrow_table = pa.Table.from_pandas(df)
imos = pa.BufferOutputStream()
_write_table(arrow_table, imos, version="2.0")
buf = imos.get_result()
reader = pa.BufferReader(buf)
df_read = _read_table(reader).to_pandas()
tm.assert_frame_equal(df, df_read)


@parquet
def test_pandas_parquet_pyfile_roundtrip(tmpdir):
filename = tmpdir.join('pandas_pyfile_roundtrip.parquet').strpath
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