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martin-g
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Nov 11, 2025
| #### Struct Type Casting | ||
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| - **Struct to Struct**: Structs can be cast to other struct types if all field types are compatible. | ||
| - Requires the same number of fields in source and target structs |
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This is not quite correct!
- - the comparison uses
Iterator.zip() - https://github.com/scala/scala/blob/v2.13.6/src/library/scala/collection/Iterator.scala#L794-L799 - but zip() does not mandate equal sizes. It just iterates over the underlying iterators until one of them has no more items. If the first struct (from) has more items than the second (to) then some of from's items will be discarded.
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Thanks @martin-g appreciate if you can provide an example. so it would be more clear for the user and we can also track this in the issue as future work
| - Recursively checks that the array element type supports casting to string | ||
| - Example: `CAST(array(1, 2, 3) AS STRING)` → `"[1, 2, 3]"` | ||
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| - **Array to Array**: Arrays can be cast to other array types if the element types are compatible. |
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There are no tests for this.
cast ArrayType to StringType seems to be the only cast ArrayType to ... test in the suite
| - Example: `CAST(array(1, 2, 3) AS ARRAY<BIGINT>)` → `array(1L, 2L, 3L)` | ||
| - The compatibility level (Compatible/Incompatible/Unsupported) is determined by the element type cast | ||
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| - **Special case**: Arrays with `NullType` elements (empty arrays) can be cast to any array type |
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Is it correct to say empty arrays here ?
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Agree with @martin-g
array(null) and array() are not quite the same
comphead
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Nov 11, 2025
comphead
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This is supergreat @andygrove
The nice follow up would be adding examples what is not supported
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Which issue does this PR close?
Closes #2743
Rationale for this change
What changes are included in this PR?
How are these changes tested?