Encoding

Functions
std::unique_ptr< column >	cudf::dictionary::encode (column_view const &column, data_type indices_type=data_type{type_id::INT32}, cuda::stream_ref stream=cudf::get_default_stream(), cudf::memory_resources mr=cudf::get_current_device_resource_ref())
	Construct a dictionary column by dictionary encoding an existing column. More...
std::unique_ptr< column >	cudf::dictionary::decode (dictionary_column_view const &dictionary_column, cuda::stream_ref stream=cudf::get_default_stream(), cudf::memory_resources mr=cudf::get_current_device_resource_ref())
	Create a column by gathering the keys from the provided dictionary_column into a new column using the indices from that column. More...

Detailed Description

Function Documentation

decode()

std::unique_ptr<column> cudf::dictionary::decode	(	dictionary_column_view const &	dictionary_column,
		cuda::stream_ref	stream = cudf::get_default_stream(),
		cudf::memory_resources	mr = cudf::get_current_device_resource_ref()
	)

#include <cudf/dictionary/encode.hpp>

Create a column by gathering the keys from the provided dictionary_column into a new column using the indices from that column.

d1 = {["a", "c", "d"], [2, 0, 1, 0]}
s = decode(d1)
s is now ["d", "a", "c", "a"]

Parameters

dictionary_column	Existing dictionary column
stream	CUDA stream used for device memory operations and kernel launches
mr	Memory resources used for temporary allocations and the returned column

Returns

New column with type matching the dictionary_column's keys

encode()

std::unique_ptr<column> cudf::dictionary::encode	(	column_view const &	column,
		data_type	indices_type = data_type{type_id::INT32},
		cuda::stream_ref	stream = cudf::get_default_stream(),
		cudf::memory_resources	mr = cudf::get_current_device_resource_ref()
	)

#include <cudf/dictionary/encode.hpp>

Construct a dictionary column by dictionary encoding an existing column.

The output column is a DICTIONARY type with a keys column of non-null, unique values that are in a strict, total order. Meaning, keys[i] is _ordered before keys[i+1] for all i in [0,n-1) where n is the number of keys.

The output column has a child indices column that is of integer type and with the same size as the input column. The indices column will be of type indices_type. The result is undefined if the indices_type is not large enough for the indices values.

The null mask and null count are copied from the input column to the output column.

Exceptions

cudf::data_type_error	if indices type is not a signed integer type
std::invalid_argument	if the column to encode is a DICTIONARY or nested type

c = [429, 111, 213, 111, 213, 429, 213]
d = encode(c)
d now has keys [111, 213, 429] and indices [2, 0, 1, 0, 1, 2, 1]

Parameters

column	The column to dictionary encode
indices_type	The integer type to use for the indices
stream	CUDA stream used for device memory operations and kernel launches
mr	Memory resources used for temporary allocations and the returned column

Returns

Returns a dictionary column