robertwb commented on a change in pull request #13488:
URL: https://github.com/apache/beam/pull/13488#discussion_r543754989
##########
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:
Good point. Done.
##########
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:
Done.
##########
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:
I actually tried to add typehints initially; they work poorly due to the
fact that this works both on bytes and strings (but it's hard for mypy to know
that it will be all one or all the other). But I added some comments at least.
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