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Adds a new introspection function that returns a struct containing the complete Arrow Field information for any expression: name, data_type, nullable, and metadata. This unifies what `arrow_typeof`, `arrow_metadata`, and `is_nullable` provide individually. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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| query ? | ||
| SELECT arrow_field(ARRAY[1,2,3]) | ||
| ---- | ||
| {name: lit, data_type: List(Int64), nullable: false, metadata: {}} |
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It would be good to have tests for more complex types like Map and Struct too! Maybe a Dictionary too.
Co-authored-by: Martin Grigorov <martin-g@users.noreply.github.com>
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My suggestions broke the build :-/ Sorry! |
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no worries @martin-g, fixed now! |
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Which issue does this PR close?
Rationale for this change
DataFusion has individual introspection functions (
arrow_typeof,arrow_metadata,is_nullable) but no single function that returns the complete ArrowFieldrepresentation. Havingarrow_field(expr)that returns a struct with all field info avoids multiple function calls when you need the full picture, and provides a natural complement to the existing introspection suite.What changes are included in this PR?
Adds
arrow_field(expr)scalar UDF that returns a struct:The returned struct has four fields:
name(Utf8) — the field namedata_type(Utf8) — the Arrow data type as stringnullable(Boolean) — whether the field is nullablemetadata(Map<Utf8, Utf8>) — the field metadataIndividual fields are accessible via bracket syntax.
Files:
datafusion/functions/src/core/arrow_field.rs— new UDF implementationdatafusion/functions/src/core/mod.rs— registrationdatafusion/sqllogictest/test_files/arrow_field.slt— testsAre these changes tested?
Yes, sqllogictest covering literals (int, null, bool, string, float, list), table columns, nullability, and struct field access.
Are there any user-facing changes?
New SQL function
arrow_field(expr)is available.🤖 Generated with Claude Code