Arrays¶
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class
arrow::Array¶ Array base type Immutable data array with some logical type and some length.
Any memory is owned by the respective Buffer instance (or its parents).
The base class is only required to have a null bitmap buffer if the null count is greater than 0
If known, the null count can be provided in the base Array constructor. If the null count is not known, pass -1 to indicate that the null count is to be computed on the first call to null_count()
Subclassed by arrow::DictionaryArray, arrow::ExtensionArray, arrow::FixedSizeListArray, arrow::FlatArray, arrow::StructArray, arrow::UnionArray
Public Functions
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bool
IsNull(int64_t i) const¶ Return true if value at index is null. Does not boundscheck.
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bool
IsValid(int64_t i) const¶ Return true if value at index is valid (not null).
Does not boundscheck
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Result<std::shared_ptr<Scalar>>
GetScalar(int64_t i) const¶ Return a Scalar containing the value of this array at i.
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int64_t
length() const¶ Size in the number of elements this array contains.
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int64_t
offset() const¶ A relative position into another array’s data, to enable zero-copy slicing.
This value defaults to zero
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int64_t
null_count() const¶ The number of null entries in the array.
If the null count was not known at time of construction (and set to a negative value), then the null count will be computed and cached on the first invocation of this function
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std::shared_ptr<Buffer>
null_bitmap() const¶ Buffer for the validity (null) bitmap, if any.
Note that Union types never have a null bitmap.
Note that for
null_count == 0or for null type, this will be null. This buffer does not account for any slice offset
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const uint8_t *
null_bitmap_data() const¶ Raw pointer to the null bitmap.
Note that for
null_count == 0or for null type, this will be null. This buffer does not account for any slice offset
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bool
Equals(const Array &arr, const EqualOptions& = EqualOptions::Defaults()) const¶ Equality comparison with another array.
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std::string
Diff(const Array &other) const¶ Return the formatted unified diff of arrow::Diff between this Array and another Array.
Approximate equality comparison with another array.
epsilon is only used if this is FloatArray or DoubleArray
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bool
RangeEquals(int64_t start_idx, int64_t end_idx, int64_t other_start_idx, const Array &other, const EqualOptions& = EqualOptions::Defaults()) const¶ Compare if the range of slots specified are equal for the given array and this array.
end_idx exclusive. This methods does not bounds check.
Construct a zero-copy view of this array with the given type.
This method checks if the types are layout-compatible. Nested types are traversed in depth-first order. Data buffers must have the same item sizes, even though the logical types may be different. An error is returned if the types are not layout-compatible.
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std::shared_ptr<Array>
Slice(int64_t offset, int64_t length) const¶ Construct a zero-copy slice of the array with the indicated offset and length.
- Return
a new object wrapped in std::shared_ptr<Array>
- Parameters
[in] offset: the position of the first element in the constructed slice[in] length: the length of the slice. If there are not enough elements in the array, the length will be adjusted accordingly
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Result<std::shared_ptr<Array>>
SliceSafe(int64_t offset, int64_t length) const¶ Input-checking variant of Array::Slice.
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Result<std::shared_ptr<Array>>
SliceSafe(int64_t offset) const¶ Input-checking variant of Array::Slice.
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std::string
ToString() const¶ - Return
PrettyPrint representation of array suitable for debugging
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bool
Concrete array subclasses¶
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class
arrow::DictionaryArray: public arrow::Array¶ Array type for dictionary-encoded data with a data-dependent dictionary.
A dictionary array contains an array of non-negative integers (the “dictionary indices”) along with a data type containing a “dictionary” corresponding to the distinct values represented in the data.
For example, the array
[“foo”, “bar”, “foo”, “bar”, “foo”, “bar”]
with dictionary [“bar”, “foo”], would have dictionary array representation
indices: [1, 0, 1, 0, 1, 0] dictionary: [“bar”, “foo”]
The indices in principle may be any integer type.
Public Functions
Transpose this DictionaryArray.
This method constructs a new dictionary array with the given dictionary type, transposing indices using the transpose map. The type and the transpose map are typically computed using DictionaryUnifier.
- Parameters
[in] type: the new type object[in] dictionary: the new dictionary[in] transpose_map: transposition array of this array’s indices into the target array’s indices[in] pool: a pool to allocate the array data from
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bool
CanCompareIndices(const DictionaryArray &other) const¶ Determine whether dictionary arrays may be compared without unification.
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std::shared_ptr<Array>
dictionary() const¶ Return the dictionary for this array, which is stored as a member of the ArrayData internal structure.
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int64_t
GetValueIndex(int64_t i) const¶ Return the ith value of indices, cast to int64_t.
Not recommended for use in performance-sensitive code. Does not validate whether the value is null or out-of-bounds.
Public Static Functions
Construct DictionaryArray from dictionary and indices array and validate.
This function does the validation of the indices and input type. It checks if all indices are non-negative and smaller than the size of the dictionary.
- Parameters
[in] type: a dictionary type[in] dictionary: the dictionary with same value type as the type object[in] indices: an array of non-negative integers smaller than the size of the dictionary
Non-nested¶
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class
FlatArray: public arrow::Array¶ Base class for non-nested arrays.
Subclassed by arrow::BaseBinaryArray< TYPE >, arrow::NullArray, arrow::PrimitiveArray, arrow::BaseBinaryArray< BinaryType >, arrow::BaseBinaryArray< LargeBinaryType >
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class
BinaryArray: public arrow::BaseBinaryArray<BinaryType>¶ Concrete Array class for variable-size binary data.
Subclassed by arrow::StringArray
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class
arrow::StringArray: public arrow::BinaryArray¶ Concrete Array class for variable-size string (utf-8) data.
Public Functions
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Status
ValidateUTF8() const¶ Validate that this array contains only valid UTF8 entries.
This check is also implied by ValidateFull()
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Status
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class
arrow::PrimitiveArray: public arrow::FlatArray¶ Base class for arrays of fixed-size logical types.
Subclassed by arrow::BooleanArray, arrow::DayTimeIntervalArray, arrow::FixedSizeBinaryArray, arrow::NumericArray< TYPE >
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class
arrow::BooleanArray: public arrow::PrimitiveArray¶ Concrete Array class for boolean data.
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class
FixedSizeBinaryArray: public arrow::PrimitiveArray¶ Concrete Array class for fixed-size binary data.
Subclassed by arrow::Decimal128Array, arrow::Decimal256Array
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class
arrow::Decimal128Array: public arrow::FixedSizeBinaryArray¶ Concrete Array class for 128-bit decimal data.
Public Functions
Construct Decimal128Array from ArrayData instance.
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template<typename
TYPE>
classNumericArray: public arrow::PrimitiveArray¶ Concrete Array class for numeric data.
Nested¶
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class
arrow::UnionArray: public arrow::Array¶ Base class for SparseUnionArray and DenseUnionArray.
Subclassed by arrow::DenseUnionArray, arrow::SparseUnionArray
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class
arrow::ListArray: public arrow::BaseListArray<ListType>¶ Concrete Array class for list data.
Subclassed by arrow::MapArray
Public Functions
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Result<std::shared_ptr<Array>>
Flatten(MemoryPool *memory_pool = default_memory_pool()) const¶ Return an Array that is a concatenation of the lists in this array.
Note that it’s different from
values()in that it takes into consideration of this array’s offsets as well as null elements backed by non-empty lists (they are skipped, thus copying may be needed).
Public Static Functions
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Result<std::shared_ptr<ListArray>>
FromArrays(const Array &offsets, const Array &values, MemoryPool *pool = default_memory_pool())¶ Construct ListArray from array of offsets and child value array.
This function does the bare minimum of validation of the offsets and input types, and will allocate a new offsets array if necessary (i.e. if the offsets contain any nulls). If the offsets do not have nulls, they are assumed to be well-formed
- Parameters
[in] offsets: Array containing n + 1 offsets encoding length and size. Must be of int32 type[in] values: Array containing list values[in] pool: MemoryPool in case new offsets array needs to be allocated because of null values
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Result<std::shared_ptr<Array>>
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class
arrow::StructArray: public arrow::Array¶ Concrete Array class for struct data.
Public Functions
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std::shared_ptr<Array>
GetFieldByName(const std::string &name) const¶ Returns null if name not found.
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Result<ArrayVector>
Flatten(MemoryPool *pool = default_memory_pool()) const¶ Flatten this array as a vector of arrays, one for each field.
- Parameters
[in] pool: The pool to allocate null bitmaps from, if necessary
Public Static Functions
Return a StructArray from child arrays and field names.
The length and data type are automatically inferred from the arguments. There should be at least one child array.
Return a StructArray from child arrays and fields.
The length is automatically inferred from the arguments. There should be at least one child array. This method does not check that field types and child array types are consistent.
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std::shared_ptr<Array>
Chunked Arrays¶
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class
arrow::ChunkedArray¶ A data structure managing a list of primitive Arrow arrays logically as one large array.
Data chunking is treated throughout this project largely as an implementation detail for performance and memory use optimization. ChunkedArray allows Array objects to be collected and interpreted as a single logical array without requiring an expensive concatenation step.
In some cases, data produced by a function may exceed the capacity of an Array (like BinaryArray or StringArray) and so returning multiple Arrays is the only possibility. In these cases, we recommend returning a ChunkedArray instead of vector of Arrays or some alternative.
When data is processed in parallel, it may not be practical or possible to create large contiguous memory allocations and write output into them. With some data types, like binary and string types, it is not possible at all to produce non-chunked array outputs without requiring a concatenation step at the end of processing.
Application developers may tune chunk sizes based on analysis of performance profiles but many developer-users will not need to be especially concerned with the chunking details.
Preserving the chunk layout/sizes in processing steps is generally not considered to be a contract in APIs. A function may decide to alter the chunking of its result. Similarly, APIs accepting multiple ChunkedArray inputs should not expect the chunk layout to be the same in each input.
Public Functions
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ChunkedArray(ArrayVector chunks)¶ Construct a chunked array from a vector of arrays.
The vector must be non-empty and all its elements must have the same data type.
Construct a chunked array from a single Array.
Construct a chunked array from a vector of arrays and a data type.
As the data type is passed explicitly, the vector may be empty.
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int64_t
length() const¶ - Return
the total length of the chunked array; computed on construction
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int64_t
null_count() const¶ - Return
the total number of nulls among all chunks
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std::shared_ptr<ChunkedArray>
Slice(int64_t offset, int64_t length) const¶ Construct a zero-copy slice of the chunked array with the indicated offset and length.
- Return
a new object wrapped in std::shared_ptr<ChunkedArray>
- Parameters
[in] offset: the position of the first element in the constructed slice[in] length: the length of the slice. If there are not enough elements in the chunked array, the length will be adjusted accordingly
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std::shared_ptr<ChunkedArray>
Slice(int64_t offset) const¶ Slice from offset until end of the chunked array.
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Result<std::vector<std::shared_ptr<ChunkedArray>>>
Flatten(MemoryPool *pool = default_memory_pool()) const¶ Flatten this chunked array as a vector of chunked arrays, one for each struct field.
- Parameters
[in] pool: The pool for buffer allocations, if any
Construct a zero-copy view of this chunked array with the given type.
Calls Array::View on each constituent chunk. Always succeeds if there are zero chunks
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bool
Equals(const ChunkedArray &other) const¶ Determine if two chunked arrays are equal.
Two chunked arrays can be equal only if they have equal datatypes. However, they may be equal even if they have different chunkings.
Determine if two chunked arrays are equal.
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std::string
ToString() const¶ - Return
PrettyPrint representation suitable for debugging
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