Improve documentation on how to build ScalarValue::Struct and add ScalarStructBuilder
#9229
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| @@ -99,6 +102,66 @@ use arrow_buffer::NullBuffer; | |||
| /// # } | |||
| /// ``` | |||
| /// | |||
| /// # Nested Types | |||
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It would be nice to have some similar examples for creating Struct::List
| /// # use arrow::datatypes::{DataType, Field}; | ||
| /// # use datafusion_common::{ScalarValue, scalar::ScalarStructBuilder}; | ||
| /// // Build a struct like: {a: 1, b: "foo"} | ||
| /// let field_a = Field::new("a", DataType::Int32, false); |
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The use case for the ScalarStructBuilder is pretty nicely illustrated by this example compared to the one in
## Example: Creating [`ScalarValue::Struct`] directly
| @@ -2710,27 +2774,6 @@ impl From<String> for ScalarValue { | |||
| } | |||
| } | |||
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| // TODO: Remove this after changing to Scalar<T> | |||
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These were added in #7893 and not yet released so this is not a breaking API change
datafusion/common/src/scalar/mod.rs
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| let struct_arr = sv.to_array().unwrap(); | ||
| let actual = as_struct_array(&struct_arr).unwrap(); | ||
| assert_eq!(actual, &expected); | ||
| } | ||
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| #[test] | ||
| #[should_panic(expected = "assertion `left == right` failed")] | ||
| #[should_panic( | ||
| expected = "Error building SclarValue::Struct. Expected array with exactly one element, found array with 4 elements" |
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the builder makes better messages I think
| @@ -932,17 +932,17 @@ fn round_trip_scalar_values() { | |||
| ScalarValue::Binary(None), | |||
| ScalarValue::LargeBinary(Some(b"bar".to_vec())), | |||
| ScalarValue::LargeBinary(None), | |||
| ScalarValue::from(( | |||
| vec
…ScalarStructBuilder`
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datafusion/common/src/scalar/mod.rs
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| @@ -15,7 +15,9 @@ | |||
| // specific language governing permissions and limitations | |||
| // under the License. | |||
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| //! This module provides ScalarValue, an enum that can be used for storage of single elements | |||
| //! [`ScalarValue`]: stores single constant values | |||
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constant may be misleading.
Maybe like
In databases, a scalar value is simply a single value, as opposed to a set of values or a combination of values. It's like having just one piece of information
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Scalar value is a single value of different datatypes: bool, ints, floats, arrays, structs, etc
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Good point -- reworded
…tafusion into alamb/better_struct_array
Which issue does this PR close?
Closes #9227
Rationale for this change
Described on #9227
Basically I found it hard to build
ScalarValue::Structafter #7893What changes are included in this PR?
ScalarStructBuilderto help ease the conversion when trying to add ScalarValues or arrays as fieldsFrom..impls forScalarValuethat were added in Change ScalarValue::Struct to ArrayRef #7893 but are of limited utilityAre these changes tested?
Yes, by doc tests
Are there any user-facing changes?