Handle field nullability on schema merges with a missing column #8851
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vegarsti
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Nov 15, 2025
| /// ); | ||
| /// ``` | ||
| pub fn try_merge(schemas: impl IntoIterator<Item = Self>) -> Result<Self, ArrowError> { | ||
| let schemas = schemas.into_iter().collect::<Vec<Self>>(); |
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This increases the memory consumption of this method. An alternative could be to change the function signature to schemas: &[Self]? But I haven't checked if that is feasible.
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I'll address the test failures, of course! |
alamb
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alamb
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Nov 15, 2025
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Thank you @brancz and @vegarsti
The topic of schema merging and comparison comes up a lot in DataFuson - i wrote some notes here: #8840 (comment)
| pub fn try_merge( | ||
| &mut self, | ||
| field: &FieldRef, | ||
| preserve_nullability: bool, |
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This would be a breaking API change, which means we would have to wait for the next major release to get it in
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Which issue does this PR close?
Closes #8840.
Rationale for this change
From the issue:
What changes are included in this PR?
Adds a
preserve_nullabilityargument toSchemaBuilder::try_mergewhich, when set totruewill preserve the current behavior of using the field's nullability. When set tofalse, the nullability of the field will always be set totrue.Are these changes tested?
Yes, existing tests (some modified), and new test.
Are there any user-facing changes?
Yes. When merging schemas, any non-nullable fields not present in all schemas will now always be nullable.