Re: [PR] GH-519: [Variant] Disambiguate SQL NULL (missing) from Variant null [parquet-format]

["Tishj (via GitHub)" <gi...@apache.org>]

Tishj commented on code in PR #520:
URL: https://github.com/apache/parquet-format/pull/520#discussion_r2336428309


##########
VariantShredding.md:
##########
@@ -42,7 +42,31 @@ Variant values are stored in Parquet fields named `value`.
 Each `value` field may have an associated shredded field named `typed_value` that stores the value when it matches a specific type.
 When `typed_value` is present, readers **must** reconstruct shredded values according to this specification.
 
-For example, a Variant field, `measurement` may be shredded as long values by adding `typed_value` with type `int64`:
+The Parquet columns used to store variant metadata and values must be accessed by name, not by position.
+
+In order to avoid ambiguity, this specification always uses the term "`null`" to mean the variant
+null value (binary encoding: `00`). The phrase "missing" or "NULL" (all caps) always refers to an
+`optional` value that is not present (= SQL NULL).

Review Comment:
   I think the last option is preferable, the spec is meant to be clear, not concise, wordy over ambiguous is always better in my opinion.



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