cloud-fan commented on code in PR #56237:
URL: https://github.com/apache/spark/pull/56237#discussion_r3338790209
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sql/core/src/test/resources/sql-tests/inputs/extract-value-resolution-edge-cases.sql:
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@@ -8,3 +8,13 @@ SELECT col1.a, a FROM t1 ORDER BY col1.a;
SELECT split(col1, '-')[1] AS a FROM VALUES('a-b') ORDER BY split(col1,
'-')[1];
DROP TABLE t1;
+
+-- SPARK-57186: extracting a field/element/key from a NullType base returns
NULL instead of
+-- throwing INVALID_EXTRACT_BASE_FIELD_TYPE (SQL NULL propagation; a NullType
column can arise e.g.
+-- from schema evolution with missing columns). This applies uniformly to
dotted field access
+-- (`col.a`) and the subscript forms (`col[0]`, `col['key']`), and is
implemented at the
+-- user-facing resolution sites (ExtractValue.applyOrNull) without changing
the shared
+-- ExtractValue.extractValue utility.
+SELECT col.a FROM (SELECT null AS col) t;
+SELECT col[0] FROM (SELECT null AS col) t;
Review Comment:
Nit: `col[0]` / `col['key']` on a `NullType` base now produce an output
column named `NULL` (analyzer plan: `Project [null AS NULL#x]`), whereas
`col.a` is named `a` and a non-null `arr[0]` would be named `arr[0]`. Cosmetic
only and an extreme edge case (NullType column + subscript), so not blocking --
just flagging the naming asymmetry in case a stable column name is preferable
here.
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