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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2021/07/22 14:22:50 UTC
[GitHub] [arrow-rs] alamb opened a new issue #598: Allow the creation of String arrays from an interator of &Option<&str>
alamb opened a new issue #598:
URL: https://github.com/apache/arrow-rs/issues/598
**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
I am making constant arrays for tests from constant slices
With 1.53 Rust introduces the ability to turn constant slices into iterators. For example. However, the collect for
This does not work:
```rust
let string_array: ArrayRef = Arc::new([Some("foo"), None, Some("bar")].into_iter().collect::<StringArray>());
```
It produces this error:
```
error[E0277]: a value of type `GenericStringArray<i32>` cannot be built from an iterator over elements of type `&Option<&str>`
--> arrow_util/src/display.rs:43:92
|
43 | let string_array: ArrayRef = Arc::new([Some("foo"), None, Some("bar")].into_iter().collect::<StringArray>());
| ^^^^^^^ value of type `GenericStringArray<i32>` cannot be built from `std::iter::Iterator<Item=&Option<&str>>`
|
= help: the trait `FromIterator<&Option<&str>>` is not implemented for `GenericStringArray<i32>`
```
But this does (for primitive arrays):
```rust
let int64_array: ArrayRef = Arc::new([Some(-1), None, Some(2)].into_iter().collect::<Int64Array>());
```
Instead, for strings we have to do
```rust
let string_array: ArrayRef = Arc::new(vec![Some("foo"), None, Some("bar")].into_iter().collect::<StringArray>());
```
**Describe the solution you'd like**
I would like to be able to do (note the lack of `vec!`):
```rust
let string_array: ArrayRef = Arc::new([Some("foo"), None, Some("bar")].into_iter().collect::<StringArray>());
```
Perhaps by making the `FromIter` implementation fancier (right now it hard codes a `Option<&str>` but the iterator above tives a `&Option<&str>`: https://github.com/apache/arrow-rs/blob/master/arrow/src/array/array_string.rs#L255-L262
**Additional context**
Note -- the same sort if issue exists for `DictionaryArray` as well
Does not work:
```rust
let dict_array = [Some("a"), None, Some("b")]
.into_iter().collect::<DictionaryArray::<Int32Type>>();
```
Does work
```rust
let dict_array = vec![Some("a"), None, Some("b")]
.into_iter().collect::<DictionaryArray::<Int32Type>>();
```
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[GitHub] [arrow-rs] alamb edited a comment on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
alamb edited a comment on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897114876
> it is 20 more characters, but it does not seem that bad?
I agree there is a straightforward workaround if you are familiar with the `arrow` crate this isn't a big deal.
However, I think the fact something that looks like it *should* work does not increases the barrier to entry for anyone who is first using the`arrow` crate or those who are not Rust experts yet
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[GitHub] [arrow-rs] alamb edited a comment on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
alamb edited a comment on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897114876
> it is 20 more characters, but it does not seem that bad?
I agree there is a straightforward workaround if you are familiar with the `arrow` crate this isn't a big deal.
However, I think fact something that looks like it *should* work it increases the barrier to entry for anyone who is first using the`arrow` crate or those who are not Rust experts yet
--
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[GitHub] [arrow-rs] alamb closed issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
alamb closed issue #598:
URL: https://github.com/apache/arrow-rs/issues/598
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[GitHub] [arrow-rs] jorgecarleitao commented on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
jorgecarleitao commented on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897119976
that is a great argument 👍
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[GitHub] [arrow-rs] jorgecarleitao commented on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
jorgecarleitao commented on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897046153
I am probably missing something. The below does not compile:
```rust
let array: StringArray = [Some("foo"), None, Some("bar")]
.iter()
.collect();
```
isn't it enough to use `.map(|x| x.as_ref())`:
```rust
let array: StringArray = [Some("foo"), None, Some("bar")]
.iter()
.map(|x| x.as_ref())
.collect();
```
it is 20 more characters, but it does not seem _that_ bad?
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[GitHub] [arrow-rs] alamb edited a comment on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
alamb edited a comment on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897114876
> it is 20 more characters, but it does not seem that bad?
I agree there is a straightforward workaround and if you are familiar with the `arrow` crate this isn't a big deal.
However, I think the fact something that looks like it *should* work does not increases the barrier to entry for anyone who is first using the`arrow` crate or those who are not Rust experts yet
--
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[GitHub] [arrow-rs] alamb commented on issue #598: Allow the creation of String arrays from an interator of &Option<&str>
Posted by GitBox <gi...@apache.org>.
alamb commented on issue #598:
URL: https://github.com/apache/arrow-rs/issues/598#issuecomment-897114876
> it is 20 more characters, but it does not seem that bad?
I agree there is a straightforward workaround if you are familiar with the `arrow` crate this isn't a big deal.
However, I think fact something that looks like it *should* work it increases the barrier to entry for anyone who is first using the`arrow` crate that something or those who are not Rust experts yet
--
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