Document repetition / definition levels more#10101
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mapleFU
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Jun 10, 2026
jhorstmann
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Jun 11, 2026
| /// * a [`StructArrayReader`] has no `empty` state — only present `d >= D` vs | ||
| /// null `d < D`. | ||
| /// | ||
| /// **Repetition level** — where a value attaches relative to this reader's list: |
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I'm now wondering whether there can actually be inconsistencies between repetition and definition levels, which might lead to different implementations interpreting the same file differently. Consider the following level data for a required list with required items:
Rep levels: [0, 1]
Def levels: [0, 1]
The first row should be an empty list according to its def level, but then then the second rep level indicates a continuation/insert into the previously started list.
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Which issue does this PR close?
Rationale for this change
While reading #9849 I spent some non trivial time reviewing definition and repetition levels and I wanted to encode this knowledge as comments for my future self.
What changes are included in this PR?
Document levels
Are these changes tested?
Doc only, covered by CI
Are there any user-facing changes?
docs only (of internal structures)