TheNeuralBit commented on a change in pull request #13488:
URL: https://github.com/apache/beam/pull/13488#discussion_r542981589
##########
File path: sdks/python/apache_beam/dataframe/io.py
##########
@@ -192,14 +207,133 @@ def expand(self, root):
self.reader,
self.args,
self.kwargs,
+ self.binary,
self.incremental,
- self.splittable,
- self.binary)))
+ self.splitter)))
from apache_beam.dataframe import convert
return convert.to_dataframe(
pcoll, proxy=_prefix_range_index_with(':', sample[:0]))
+class _Splitter:
+ def empty_buffer(self):
+ raise NotImplementedError(self)
+
+ def read_header(self, handle):
+ raise NotImplementedError(self)
+
+ def read_to_record_boundary(self, buffered, handle):
+ raise NotImplementedError(self)
Review comment:
Could you add docstrings and/or typehints for this class so its clear
what implementations should do
##########
File path: sdks/python/apache_beam/dataframe/io.py
##########
@@ -192,14 +207,134 @@ def expand(self, root):
self.reader,
self.args,
self.kwargs,
+ self.binary,
self.incremental,
- self.splittable,
- self.binary)))
+ self.splitter)))
from apache_beam.dataframe import convert
return convert.to_dataframe(
pcoll, proxy=_prefix_range_index_with(':', sample[:0]))
+class _Splitter:
+ def empty_buffer(self):
+ raise NotImplementedError(self)
+
+ def read_header(self, handle):
+ raise NotImplementedError(self)
+
+ def read_to_record_boundary(self, buffered, handle):
+ raise NotImplementedError(self)
+
+
+class _DelimSplitter(_Splitter):
+ def __init__(self, delim, read_chunk_size=_DEFAULT_BYTES_CHUNKSIZE):
Review comment:
Might be helpful to clarify that this is splitting on delimiters between
_records_, it's easy to get mixed up in the CSV case where there's also a field
delimiter.
```suggestion
class _RecordDelimSplitter(_Splitter):
""" A _Splitter that splits on delimiters between records. """
def __init__(self, delim, read_chunk_size=_DEFAULT_BYTES_CHUNKSIZE):
```
##########
File path: sdks/python/apache_beam/dataframe/io.py
##########
@@ -31,16 +33,28 @@
_DEFAULT_BYTES_CHUNKSIZE = 1 << 20
-def read_csv(path, *args, **kwargs):
+def read_csv(path, *args, splittable=False, **kwargs):
"""Emulates `pd.read_csv` from Pandas, but as a Beam PTransform.
Use this as
df = p | beam.dataframe.io.read_csv(...)
to get a deferred Beam dataframe representing the contents of the file.
+
+ If your files are large and records do not contain quoted newlines, you may
+ pass the extra argument splittable=True to enable dynamic splitting for this
+ read.
Review comment:
Can we make this warn that using splittable=True with quoted newlines
could lead to dataloss?
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