fix: allow unnesting to bring struct fields into scope

sqlglot/optimizer/qualify_columns.py

@@ -7,6 +7,7 @@
 from sqlglot.dialects.dialect import Dialect, DialectType
 from sqlglot.errors import OptimizeError
 from sqlglot.helper import seq_get, SingleValuedMapping
+from sqlglot.optimizer.annotate_types import annotate_types
 from sqlglot.optimizer.scope import Scope, build_scope, traverse_scope, walk_in_scope
 from sqlglot.optimizer.simplify import simplify_parens
 from sqlglot.schema import Schema, ensure_schema
@@ -652,8 +653,19 @@ def get_source_columns(self, name: str, only_visible: bool = False) -> t.Sequenc
 
         if isinstance(source, exp.Table):
             columns = self.schema.column_names(source, only_visible)
-        elif isinstance(source, Scope) and isinstance(source.expression, exp.Values):
-            columns = source.expression.alias_column_names
+        elif isinstance(source, Scope) and isinstance(source.expression, (exp.Values, exp.Unnest)):
+            columns = source.expression.named_selects
+
+            # in bigquery, unnest structs are automatically scoped as tables, so you can
+            # directly select a struct field in a query.
+            # this handles the case where the unnest is statically defined.
+            if self.schema.dialect == "bigquery":
+                expression = source.expression
+                annotate_types(expression)
+
+                if expression.is_type(exp.DataType.Type.STRUCT):
+                    for k in expression.type.expressions:  # type: ignore
+                        columns.append(k.name)
         else:
             columns = source.expression.named_selects
 

tests/fixtures/optimizer/qualify_columns.sql

@@ -492,6 +492,11 @@ SELECT x AS x, offset AS offset FROM UNNEST([1, 2]) AS x WITH OFFSET AS offset;
 select * from unnest ([1, 2]) as x with offset as y;
 SELECT x AS x, y AS y FROM UNNEST([1, 2]) AS x WITH OFFSET AS y;
 
+# dialect: bigquery
+# execute: false
+select x, a, x.a from unnest([STRUCT(1 AS a)]) as x;
+SELECT x AS x, a AS a, x.a AS a FROM UNNEST([STRUCT(1 AS a)]) AS x;
+
 # dialect: presto
 SELECT x.a, i.b FROM x CROSS JOIN UNNEST(SPLIT(CAST(b AS VARCHAR), ',')) AS i(b);
 SELECT x.a AS a, i.b AS b FROM x AS x CROSS JOIN UNNEST(SPLIT(CAST(x.b AS VARCHAR), ',')) AS i(b);