ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile #494

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1009423
Add read_row_group / num_row_groups to ParquetFile
wesm Apr 5, 2017
126789a
Fix docstring
wesm Apr 5, 2017
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17 changes: 12 additions & 5 deletions python/pyarrow/_parquet.pxd
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

@staticmethod
unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
shared_ptr[CFileMetaData] metadata();
shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

cdef cppclass FileReader:
FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
CStatus ReadColumn(int i, shared_ptr[CArray]* out);
CStatus ReadTable(shared_ptr[CTable]* out);
CStatus ReadColumn(int i, shared_ptr[CArray]* out)

int num_row_groups()
CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
CStatus ReadRowGroup(int i, const vector[int]& column_indices,
shared_ptr[CTable]* out)

CStatus ReadTable(shared_ptr[CTable]* out)
CStatus ReadTable(const vector[int]& column_indices,
shared_ptr[CTable]* out);
const ParquetFileReader* parquet_reader();
shared_ptr[CTable]* out)

const ParquetFileReader* parquet_reader()

void set_num_threads(int num_threads)

Expand Down
37 changes: 29 additions & 8 deletions python/pyarrow/_parquet.pyx
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
result.init(metadata)
return result

def read(self, column_indices=None, nthreads=1):
property num_row_groups:

def __get__(self):
return self.reader.get().num_row_groups()

def set_num_threads(self, int nthreads):
self.reader.get().set_num_threads(nthreads)

def read_row_group(self, int i, column_indices=None):
cdef:
Table table = Table()
shared_ptr[CTable] ctable
vector[int] c_column_indices

self.reader.get().set_num_threads(nthreads)
if column_indices is not None:
for index in column_indices:
c_column_indices.push_back(index)

with nogil:
check_status(self.reader.get()
.ReadRowGroup(i, c_column_indices, &ctable))
else:
# Read all columns
with nogil:
check_status(self.reader.get()
.ReadRowGroup(i, &ctable))
return table_from_ctable(ctable)

def read_all(self, column_indices=None):
cdef:
shared_ptr[CTable] ctable
vector[int] c_column_indices

if column_indices is not None:
# Read only desired column indices
for index in column_indices:
c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
with nogil:
check_status(self.reader.get()
.ReadTable(&ctable))

table.init(ctable)
return table
return table_from_ctable(ctable)

def column_name_idx(self, column_name):
"""
Expand Down
53 changes: 39 additions & 14 deletions python/pyarrow/parquet.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
def schema(self):
return self.metadata.schema

def read(self, nrows=None, columns=None, nthreads=1):
@property
def num_row_groups(self):
return self.reader.num_row_groups

def read_row_group(self, i, columns=None, nthreads=1):
"""
Read a single row group from a Parquet file

Parameters
----------
columns: list
If not None, only these columns will be read from the row group.
nthreads : int, default 1
Number of columns to read in parallel. If > 1, requires that the
underlying file source is threadsafe

Returns
-------
pyarrow.table.Table
Content of the row group as a table (of columns)
"""
column_indices = self._get_column_indices(columns)
self.reader.set_num_threads(nthreads)
return self.reader.read_row_group(i, column_indices=column_indices)

def read(self, columns=None, nthreads=1):
"""
Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
pyarrow.table.Table
Content of the file as a table (of columns)
"""
if nrows is not None:
raise NotImplementedError("nrows argument")
column_indices = self._get_column_indices(columns)
self.reader.set_num_threads(nthreads)
return self.reader.read_all(column_indices=column_indices)

if columns is None:
column_indices = None
def _get_column_indices(self, column_names):
if column_names is None:
return None
else:
column_indices = [self.reader.column_name_idx(column)
for column in columns]

return self.reader.read(column_indices=column_indices,
nthreads=nthreads)
return [self.reader.column_name_idx(column)
for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
use_dictionary=True, compression='snappy', **kwargs):
"""
Write a Table to Parquet format

Parameters
----------
table : pyarrow.Table
sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
The maximum number of rows in each Parquet RowGroup. As a default,
we will write a single RowGroup per file.
version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
compression : str or dict
Specify the compression codec, either on a general basis or per-column.
"""
row_group_size = kwargs.get('chunk_size', row_group_size)
writer = ParquetWriter(sink, use_dictionary=use_dictionary,
compression=compression,
version=version)
writer.write_table(table, row_group_size=chunk_size)
writer.write_table(table, row_group_size=row_group_size)
29 changes: 29 additions & 0 deletions python/pyarrow/tests/test_parquet.py
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
# ARROW-471
N, K = 10000, 4
df = alltypes_sample(size=N)

a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

buf = io.BytesIO()
pq.write_table(a_table, buf, row_group_size=N / K,
compression='snappy', version='2.0')

buf.seek(0)

pf = pq.ParquetFile(buf)

assert pf.num_row_groups == K

row_groups = [pf.read_row_group(i) for i in range(K)]
result = pa.concat_tables(row_groups)
pdt.assert_frame_equal(df, result.to_pandas())

cols = df.columns[:2]
row_groups = [pf.read_row_group(i, columns=cols)
for i in range(K)]
result = pa.concat_tables(row_groups)
pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
nfiles = 10
Expand Down
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Closed

wesm
wants to merge
2
commits into

from

 Closed


ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Closed

wesm
wants to merge
2
commits into

from

 Closed


ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile#494

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 Closed

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commits into

from

 Closed


ARROW-771: [Python] Add read_row_group / num_row_groups to ParquetFile
#494
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1009423

Add read_row_group / num_row_groups to ParquetFile


wesm Apr 5, 2017
126789a

Fix docstring


wesm Apr 5, 2017

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17 changes: 12 additions & 5 deletions
python/pyarrow/_parquet.pxd

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -179,7 +179,7 @@ cdef extern from "parquet/api/reader.h" namespace "parquet" nogil:

 @staticmethod
 unique_ptr[ParquetFileReader] OpenFile(const c_string& path)
 shared_ptr[CFileMetaData] metadata();
 shared_ptr[CFileMetaData] metadata()


cdef extern from "parquet/api/writer.h" namespace "parquet" nogil:
Expand DownExpand Up@@ -211,11 +211,18 @@ cdef extern from "parquet/arrow/reader.h" namespace "parquet::arrow" nogil:

 cdef cppclass FileReader:
 FileReader(CMemoryPool* pool, unique_ptr[ParquetFileReader] reader)
 CStatus ReadColumn(int i, shared_ptr[CArray]* out);
 CStatus ReadTable(shared_ptr[CTable]* out);
 CStatus ReadColumn(int i, shared_ptr[CArray]* out)

 int num_row_groups()
 CStatus ReadRowGroup(int i, shared_ptr[CTable]* out)
 CStatus ReadRowGroup(int i, const vector[int]& column_indices,
 shared_ptr[CTable]* out)

 CStatus ReadTable(shared_ptr[CTable]* out)
 CStatus ReadTable(const vector[int]& column_indices,
 shared_ptr[CTable]* out);
 const ParquetFileReader* parquet_reader();
 shared_ptr[CTable]* out)

 const ParquetFileReader* parquet_reader()

 void set_num_threads(int num_threads)

Expand Down

37 changes: 29 additions & 8 deletions
python/pyarrow/_parquet.pyx

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -31,7 +31,7 @@ from pyarrow.error import ArrowException
from pyarrow.error cimport check_status
from pyarrow.io import NativeFile
from pyarrow.memory cimport MemoryPool, maybe_unbox_memory_pool
from pyarrow.table cimport Table
from pyarrow.table cimport Table, table_from_ctable

from pyarrow.io cimport NativeFile, get_reader, get_writer

Expand DownExpand Up@@ -381,16 +381,39 @@ cdef class ParquetReader:
 result.init(metadata)
 return result

 def read(self, column_indices=None, nthreads=1):
 property num_row_groups:

 def __get__(self):
 return self.reader.get().num_row_groups()

 def set_num_threads(self, int nthreads):
 self.reader.get().set_num_threads(nthreads)

 def read_row_group(self, int i, column_indices=None):
 cdef:
 Table table = Table()
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 self.reader.get().set_num_threads(nthreads)
 if column_indices is not None:
 for index in column_indices:
 c_column_indices.push_back(index)

 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, c_column_indices, &ctable))
 else:
 # Read all columns
 with nogil:
 check_status(self.reader.get()
 .ReadRowGroup(i, &ctable))
 return table_from_ctable(ctable)

 def read_all(self, column_indices=None):
 cdef:
 shared_ptr[CTable] ctable
 vector[int] c_column_indices

 if column_indices is not None:
 # Read only desired column indices
 for index in column_indices:
 c_column_indices.push_back(index)

Expand All@@ -402,9 +425,7 @@ cdef class ParquetReader:
 with nogil:
 check_status(self.reader.get()
 .ReadTable(&ctable))

 table.init(ctable)
 return table
 return table_from_ctable(ctable)

 def column_name_idx(self, column_name):
 """
Expand Down

53 changes: 39 additions & 14 deletions
python/pyarrow/parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -50,7 +50,32 @@ def metadata(self):
 def schema(self):
 return self.metadata.schema

 def read(self, nrows=None, columns=None, nthreads=1):
 @property
 def num_row_groups(self):
 return self.reader.num_row_groups

 def read_row_group(self, i, columns=None, nthreads=1):
 """
 Read a single row group from a Parquet file

 Parameters
 ----------
 columns: list
 If not None, only these columns will be read from the row group.
 nthreads : int, default 1
 Number of columns to read in parallel. If > 1, requires that the
 underlying file source is threadsafe

 Returns
 -------
 pyarrow.table.Table
 Content of the row group as a table (of columns)
 """
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_row_group(i, column_indices=column_indices)

 def read(self, columns=None, nthreads=1):
 """
 Read a Table from Parquet format

Expand All@@ -67,17 +92,16 @@ def read(self, nrows=None, columns=None, nthreads=1):
 pyarrow.table.Table
 Content of the file as a table (of columns)
 """
 if nrows is not None:
 raise NotImplementedError("nrows argument")
 column_indices = self._get_column_indices(columns)
 self.reader.set_num_threads(nthreads)
 return self.reader.read_all(column_indices=column_indices)

 if columns is None:
 column_indices = None
 def _get_column_indices(self, column_names):
 if column_names is None:
 return None
 else:
 column_indices = [self.reader.column_name_idx(column)
 for column in columns]

 return self.reader.read(column_indices=column_indices,
 nthreads=nthreads)
 return [self.reader.column_name_idx(column)
 for column in column_names]


def read_table(source, columns=None, nthreads=1, metadata=None):
Expand DownExpand Up@@ -178,16 +202,16 @@ def open_file(path, meta=None):
 return all_data


def write_table(table, sink, chunk_size=None, version='1.0',
 use_dictionary=True, compression='snappy'):
def write_table(table, sink, row_group_size=None, version='1.0',
 use_dictionary=True, compression='snappy', **kwargs):
 """
 Write a Table to Parquet format

 Parameters
 ----------
 table : pyarrow.Table
 sink: string or pyarrow.io.NativeFile
chunk_size : int, default None
row_group_size : int, default None
 The maximum number of rows in each Parquet RowGroup. As a default,
 we will write a single RowGroup per file.
 version : {"1.0", "2.0"}, default "1.0"
Expand All@@ -198,7 +222,8 @@ def write_table(table, sink, chunk_size=None, version='1.0',
 compression : str or dict
 Specify the compression codec, either on a general basis or per-column.
 """
 row_group_size = kwargs.get('chunk_size', row_group_size)
 writer = ParquetWriter(sink, use_dictionary=use_dictionary,
 compression=compression,
 version=version)
 writer.write_table(table, row_group_size=chunk_size)
 writer.write_table(table, row_group_size=row_group_size)

29 changes: 29 additions & 0 deletions
python/pyarrow/tests/test_parquet.py

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -402,6 +402,35 @@ def test_pass_separate_metadata():
 pdt.assert_frame_equal(df, fileh.read().to_pandas())


@parquet
def test_read_single_row_group():
 # ARROW-471
 N, K = 10000, 4
 df = alltypes_sample(size=N)

 a_table = pa.Table.from_pandas(df, timestamps_to_ms=True)

 buf = io.BytesIO()
 pq.write_table(a_table, buf, row_group_size=N / K,
 compression='snappy', version='2.0')

 buf.seek(0)

 pf = pq.ParquetFile(buf)

 assert pf.num_row_groups == K

 row_groups = [pf.read_row_group(i) for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df, result.to_pandas())

 cols = df.columns[:2]
 row_groups = [pf.read_row_group(i, columns=cols)
 for i in range(K)]
 result = pa.concat_tables(row_groups)
 pdt.assert_frame_equal(df[cols], result.to_pandas())


@parquet
def test_read_multiple_files(tmpdir):
 nfiles = 10
Expand Down