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Lists Filtering#

group lists_filtering

Functions

std::unique_ptr<column> apply_boolean_mask(lists_column_view const &input, lists_column_view const &boolean_mask, rmm::cuda_stream_view stream = cudf::get_default_stream(), rmm::mr::device_memory_resource *mr = rmm::mr::get_current_device_resource())#

Filters elements in each row of input LIST column using boolean_mask LIST of booleans as a mask.

Given an input LIST column and a list-of-bools column, the function produces a new LIST column of the same type as input, where each element is copied from the input row only if the corresponding boolean_mask is non-null and true.

E.g. 

input        = { {0,1,2}, {3,4}, {5,6,7}, {8,9} };
boolean_mask = { {0,1,1}, {1,0}, {1,1,1}, {0,0} };
results      = { {1,2},   {3},   {5,6,7}, {} };

input and boolean_mask must have the same number of rows. The output column has the same number of rows as the input column. An element is copied to an output row only if the corresponding boolean_mask element is true. An output row is invalid only if the input row is invalid.

Throws:

  • cudf::logic_error – if boolean_mask is not a “lists of bools” column

  • cudf::logic_error – if input and boolean_mask have different number of rows

Parameters:

  • input – The input list column view to be filtered

  • boolean_mask – A nullable list of bools column used to filter input elements

  • stream – CUDA stream used for device memory operations and kernel launches

  • mr – Device memory resource used to allocate the returned table’s device memory

Returns:

List column of the same type as input, containing filtered list rows

std::unique_ptr<column> distinct(lists_column_view const &input, null_equality nulls_equal = null_equality::EQUAL, nan_equality nans_equal = nan_equality::ALL_EQUAL, rmm::cuda_stream_view stream = cudf::get_default_stream(), rmm::mr::device_memory_resource *mr = rmm::mr::get_current_device_resource())#

Create a new list column without duplicate elements in each list.

Given a lists column input, distinct elements of each list are copied to the corresponding output list. The order of lists is preserved while the order of elements within each list is not guaranteed.

Example: 

input  = { {0, 1, 2, 3, 2}, {3, 1, 2}, null, {4, null, null, 5} }
result = { {0, 1, 2, 3}, {3, 1, 2}, null, {4, null, 5} }

Parameters:

  • input – The input lists column

  • nulls_equal – Flag to specify whether null elements should be considered as equal

  • nans_equal – Flag to specify whether floating-point NaNs should be considered as equal

  • stream – CUDA stream used for device memory operations and kernel launches

  • mr – Device memory resource used to allocate the returned object

Returns:

The resulting lists column containing lists without duplicates

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