fix: sqllogictest failing in Substrait round-trip mode #19707
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gabotechs
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Jan 9, 2026
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| /// Used for the arrow type [`DataType::FixedSizeList`]. | ||
| /// | ||
| /// The size of the fixed list is encoded by adding it to this base value. | ||
| /// For example, `FixedSizeList(10)` would use variation reference `3 + 10 = 13`. | ||
| /// | ||
| /// [`DataType::FixedSizeList`]: datafusion::arrow::datatypes::DataType::FixedSizeList | ||
| pub const FIXED_SIZE_LIST_TYPE_VARIATION_REF: u32 = 3; |
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This is a smart way of representing the size of a list!
However, I imagine this can easily backfire in the future if different type variation refs are needed for lists, as this approach eliminates the option to add new ones.
I see two possible paths forward:
- Convince the Substrait community that adding a new FixedSizeList type to the Substrait specification is worth it. There's an open issue about this Support FixedSizeList type substrait-io/substrait#873
- Implement this as a user defined type, same as what we did for Float16: https://github.com/apache/datafusion/blob/main/datafusion/substrait/src/logical_plan/producer/types.rs#L111-L120
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Hmm, I didn't think of that. Thanks for pointing that out.
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Which issue does this PR close?
Rationale for this change
Sqllogictest was failing in Substrait round trip
What changes are included in this PR?
types.rs Producer encodes FixedSizeList as Substrait List with variation ref 3 + size. Consumer decodes back when variation ref >= 3.
Are these changes tested?
Yes
Are there any user-facing changes?