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Doctests for UnionBuilder and UnionArray. #603

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Jul 26, 2021
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Doctests for UnionBuilder and UnionArray. #603

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3325a87
Doctests for UnionBuilder and UnionArray.
novemberkilo Jul 25, 2021
1d49007
Update arrow/src/array/array_union.rs
novemberkilo Jul 25, 2021
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69 changes: 11 additions & 58 deletions arrow/src/array/array_union.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,64 +15,8 @@
// specific language governing permissions and limitations
// under the License.

//! Contains the `UnionArray` type.
//!
//! Each slot in a `UnionArray` can have a value chosen from a number of types. Each of the
//! possible types are named like the fields of a [`StructArray`](crate::array::StructArray).
//! A `UnionArray` can have two possible memory layouts, "dense" or "sparse". For more information
//! on please see the [specification](https://arrow.apache.org/docs/format/Columnar.html#union-layout).
//!
//! Builders are provided for `UnionArray`'s involving primitive types. `UnionArray`'s of nested
//! types are also supported but not via `UnionBuilder`, see the tests for examples.
//!
//! # Example: Dense Memory Layout
//!
//! ```
//! use arrow::array::UnionBuilder;
//! use arrow::datatypes::{Float64Type, Int32Type};
//!
//! # fn main() -> arrow::error::Result<()> {
//! let mut builder = UnionBuilder::new_dense(3);
//! builder.append::<Int32Type>("a", 1).unwrap();
//! builder.append::<Float64Type>("b", 3.0).unwrap();
//! builder.append::<Int32Type>("a", 4).unwrap();
//! let union = builder.build().unwrap();
//!
//! assert_eq!(union.type_id(0), 0_i8);
//! assert_eq!(union.type_id(1), 1_i8);
//! assert_eq!(union.type_id(2), 0_i8);
//!
//! assert_eq!(union.value_offset(0), 0_i32);
//! assert_eq!(union.value_offset(1), 0_i32);
//! assert_eq!(union.value_offset(2), 1_i32);
//!
//! # Ok(())
//! # }
//! ```
//!
//! # Example: Sparse Memory Layout
//! ```
//! use arrow::array::UnionBuilder;
//! use arrow::datatypes::{Float64Type, Int32Type};
//!
//! # fn main() -> arrow::error::Result<()> {
//! let mut builder = UnionBuilder::new_sparse(3);
//! builder.append::<Int32Type>("a", 1).unwrap();
//! builder.append::<Float64Type>("b", 3.0).unwrap();
//! builder.append::<Int32Type>("a", 4).unwrap();
//! let union = builder.build().unwrap();
//!
//! assert_eq!(union.type_id(0), 0_i8);
//! assert_eq!(union.type_id(1), 1_i8);
//! assert_eq!(union.type_id(2), 0_i8);
//!
//! assert_eq!(union.value_offset(0), 0_i32);
//! assert_eq!(union.value_offset(1), 1_i32);
//! assert_eq!(union.value_offset(2), 2_i32);
//!
//! # Ok(())
//! # }
//! ```
/// Contains the `UnionArray` type.
///
use crate::array::{data::count_nulls, make_array, Array, ArrayData, ArrayRef};
use crate::buffer::Buffer;
use crate::datatypes::*;
Expand All @@ -83,6 +27,15 @@ use std::any::Any;
use std::mem::size_of;

/// An Array that can represent slots of varying types.
///
/// Each slot in a `UnionArray` can have a value chosen from a number of types. Each of the
/// possible types are named like the fields of a [`StructArray`](crate::array::StructArray).
/// A `UnionArray` can have two possible memory layouts, "dense" or "sparse". For more information
/// on please see the [specification](https://arrow.apache.org/docs/format/Columnar.html#union-layout).
///
/// Builders are provided for `UnionArray`'s involving primitive types. `UnionArray`'s of nested
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/// types are also supported but not via `UnionBuilder`, see the tests for examples.
///
pub struct UnionArray {
data: ArrayData,
boxed_fields: Vec<ArrayRef>,
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41 changes: 41 additions & 0 deletions arrow/src/array/builder.rs
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Expand Up @@ -1696,6 +1696,47 @@ impl FieldData {
}

/// Builder type for creating a new `UnionArray`.
///
/// Example: **Dense Memory Layout**
///
/// ```
/// use arrow::array::UnionBuilder;
/// use arrow::datatypes::{Float64Type, Int32Type};
///
/// let mut builder = UnionBuilder::new_dense(3);
/// builder.append::<Int32Type>("a", 1).unwrap();
/// builder.append::<Float64Type>("b", 3.0).unwrap();
/// builder.append::<Int32Type>("a", 4).unwrap();
/// let union = builder.build().unwrap();
///
/// assert_eq!(union.type_id(0), 0_i8);
/// assert_eq!(union.type_id(1), 1_i8);
/// assert_eq!(union.type_id(2), 0_i8);
///
/// assert_eq!(union.value_offset(0), 0_i32);
/// assert_eq!(union.value_offset(1), 0_i32);
/// assert_eq!(union.value_offset(2), 1_i32);
/// ```
///
/// Example: **Sparse Memory Layout**
/// ```
/// use arrow::array::UnionBuilder;
/// use arrow::datatypes::{Float64Type, Int32Type};
///
/// let mut builder = UnionBuilder::new_sparse(3);
/// builder.append::<Int32Type>("a", 1).unwrap();
/// builder.append::<Float64Type>("b", 3.0).unwrap();
/// builder.append::<Int32Type>("a", 4).unwrap();
/// let union = builder.build().unwrap();
///
/// assert_eq!(union.type_id(0), 0_i8);
/// assert_eq!(union.type_id(1), 1_i8);
/// assert_eq!(union.type_id(2), 0_i8);
///
/// assert_eq!(union.value_offset(0), 0_i32);
/// assert_eq!(union.value_offset(1), 1_i32);
/// assert_eq!(union.value_offset(2), 2_i32);
/// ```
#[derive(Debug)]
pub struct UnionBuilder {
/// The current number of slots in the array
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