kennknowles commented on a change in pull request #14992:
URL: https://github.com/apache/beam/pull/14992#discussion_r651203658
##########
File path: sdks/python/apache_beam/dataframe/frames.py
##########
@@ -3210,17 +3230,15 @@ class _DeferredGroupByCols(frame_base.DeferredFrame):
diff = frame_base._elementwise_method('diff', base=DataFrameGroupBy)
fillna = frame_base._elementwise_method('fillna', base=DataFrameGroupBy)
filter = frame_base._elementwise_method('filter', base=DataFrameGroupBy)
- first = frame_base.wont_implement_method(
- DataFrameGroupBy, 'first', reason="order-sensitive")
+ first = frame_base._elementwise_method('first', base=DataFrameGroupBy)
Review comment:
Putting it here cause it to do a `first` globally?
##########
File path: sdks/python/apache_beam/dataframe/frames.py
##########
@@ -253,6 +253,36 @@ def fillna(self, value, method, axis, limit, **kwargs):
backfill = _fillna_alias('backfill')
pad = _fillna_alias('pad')
+ @frame_base.with_docs_from(pd.DataFrame)
+ def first(self, offset):
+ per_partition = expressions.ComputedExpression(
+ 'first-per-partition',
+ lambda df: df.sort_index().first(offset=offset), [self._expr],
+ preserves_partition_by=partitionings.Arbitrary(),
+ requires_partition_by=partitionings.Arbitrary())
+ with expressions.allow_non_parallel_operations(True):
+ return frame_base.DeferredFrame.wrap(
+ expressions.ComputedExpression(
+ 'first',
+ lambda df: df.sort_index().first(offset=offset), [per_partition],
+ preserves_partition_by=partitionings.Arbitrary(),
+ requires_partition_by=partitionings.Singleton()))
Review comment:
This is the bit that causes it to feed in the whole dataframe to the
DoFn at once?
##########
File path: sdks/python/apache_beam/dataframe/frames.py
##########
@@ -253,6 +253,36 @@ def fillna(self, value, method, axis, limit, **kwargs):
backfill = _fillna_alias('backfill')
pad = _fillna_alias('pad')
+ @frame_base.with_docs_from(pd.DataFrame)
+ def first(self, offset):
+ per_partition = expressions.ComputedExpression(
+ 'first-per-partition',
+ lambda df: df.sort_index().first(offset=offset), [self._expr],
+ preserves_partition_by=partitionings.Arbitrary(),
Review comment:
Assuming this means that it preserves no partitioning?
##########
File path: sdks/python/apache_beam/dataframe/frames.py
##########
@@ -3037,10 +3059,8 @@ def do_partition_apply(df):
tail = frame_base.wont_implement_method(
DataFrameGroupBy, 'tail', explanation=_PEEK_METHOD_EXPLANATION)
- first = frame_base.wont_implement_method(
- DataFrameGroupBy, 'first', reason='order-sensitive')
- last = frame_base.wont_implement_method(
- DataFrameGroupBy, 'last', reason='order-sensitive')
+ first = frame_base.not_implemented_method('first')
Review comment:
What's the difference here? I was looking at adjacent lines to see if
there were any analogous functions, to understand at a high level, but I don't
see any.
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