fix: Allow writing data with missing optional map fields #2797
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When writing data to a table with an optional map field, the schema compatibility check incorrectly failed if the data was missing that field. This happened because the validator descended into the map's internal key field (which is always required) even when the parent map field was optional and missing. The fix modifies _SchemaCompatibilityVisitor.field() to skip child validation when an optional parent field is missing from the provided schema. Closes apache#2684
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Fokko
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Dec 8, 2025
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This makes sense to me, thanks for fixing this edge case 👍
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Summary
_SchemaCompatibilityVisitor.field()to skip child validation when optional parent is missingRoot Cause
When writing data to a table with an optional map field, the schema compatibility check incorrectly failed if the data was missing that field. This happened because the validator descended into the map's internal key field (which is always
required=Trueper Iceberg spec) even when the parent map field was optional and missing.The Fix
Modified
_SchemaCompatibilityVisitor.field()inpyiceberg/schema.pyto check if the field exists in the provided schema before descending into children. If an optional parent field is missing, we skip child validation entirely.Test plan
make lint)