Weijun-H commented on code in PR #11969:
URL: https://github.com/apache/datafusion/pull/11969#discussion_r1718382099
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datafusion/sqllogictest/test_files/map.slt:
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@@ -493,3 +509,68 @@ select cardinality(map([1, 2, 3], ['a', 'b', 'c'])),
cardinality(MAP {'a': 1, 'b
cardinality(MAP {'a': MAP {1:'a', 2:'b', 3:'c'}, 'b': MAP {2:'c',
4:'d'} });
----
3 2 0 2
+
+# map_extract
+# key is string
+query IIII
+select map_extract(MAP {'a': 1, 'b': NULL, 'c': 3}, 'a'), map_extract(MAP
{'a': 1, 'b': NULL, 'c': 3}, 'b'),
+ map_extract(MAP {'a': 1, 'b': NULL, 'c': 3}, 'c'), map_extract(MAP
{'a': 1, 'b': NULL, 'c': 3}, 'd');
+----
+1 NULL 3 NULL
Review Comment:
I find it unintuitive to return a list in this context because, in a Map,
each key is unique by definition. Returning a list implies the possibility of
multiple values for a single key, which contradicts the core concept of how a
Map operates. The key uniqueness in a Map should naturally lead to a single
value or `NULL`, making a list redundant and potentially confusing. I
refactored the code so it can avoid to make special implementations for each
type of key now.
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