amol- commented on code in PR #13409:
URL: https://github.com/apache/arrow/pull/13409#discussion_r913871729
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python/pyarrow/_dataset.pyx:
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@@ -432,6 +443,46 @@ cdef class Dataset(_Weakrefable):
use_threads=use_threads,
coalesce_keys=coalesce_keys,
output_type=InMemoryDataset)
+cdef class FilteredDataset(Dataset):
+ """
+ A Dataset with an applied filter.
+
+ Parameters
+ ----------
+ dataset : Dataset
+ The dataset to which the filter should be applied.
+ expression : Expression
+ The filter that should be applied to the dataset.
+ """
+
+ def __init__(self, dataset, expression):
+ self.init(<shared_ptr[CDataset]>(<Dataset>dataset).wrapped)
+ self._filter = expression
+
+ cdef void init(self, const shared_ptr[CDataset]& sp):
+ Dataset.init(self, sp)
+ self._filter = None
+
+ def filter(self, expression):
+ cdef:
+ FilteredDataset filtered_dataset
+
+ if self._filter is not None:
+ new_filter = self._filter & expression
+ else:
+ new_filter = expression
+ filtered_dataset = self.__class__.__new__(self.__class__)
+ filtered_dataset.init(self.wrapped)
+ filtered_dataset._filter = new_filter
+ return filtered_dataset
+
+ cdef Scanner _make_scanner(self, options):
+ scanner_options = dict(options, filter=self._filter)
+ return Scanner.from_dataset(self, **scanner_options)
Review Comment:
My original code was overwriting any filter provided in `options` with the
one in `self._filter` (as providing a filter to `_make_scanner` shouldn't be
done. With the code you suggested it's going to error, which might even be
better, but it's probably going to error with an unrelated error like `got
multiple values for keyword argument 'x'` which might be confusing for the user.
I guess I can just trap if `filter` is provided in options.
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