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Type coercion fails for MAP literals with NULL values across a VALUES list #23474
Description
Describe the bug
A MAP {'key': NULL} literal in a VALUES list fails type coercion when other rows in the same list have a concrete value type. The bare NULL gets inferred as Null type instead of being coerced to the value type of the surrounding rows.
Surfaced while writing sqllogictest coverage in #23406 for #15428. Broader context: NULL literal type inference across a VALUES list works for scalar types (e.g. VALUES (1), (NULL) coerces NULL to Int64), but the same inference does not extend into the value type of a Map literal. An explicit CAST(NULL AS BIGINT) is currently required as a workaround, which is what map.slt uses.
To Reproduce
Run against DataFusion main (also reproduces on DataFusion CLI v54.0.0):
CREATE TABLE t AS VALUES
(MAP {'k1': 1, 'k2': 2}),
(MAP {'k1': NULL});Actual error:
Error during planning: Inconsistent data type across values list at row 1 column 0. Was Map("entries": non-null Struct("key": non-null Utf8, "value": Int64), unsorted) but found Map("entries": non-null Struct("key": non-null Utf8, "value": Null), unsorted)
Workaround: an explicit cast works:
CREATE TABLE t AS VALUES
(MAP {'k1': 1, 'k2': 2}),
(MAP {'k1': NULL});Expected behaviour
The bare NULL in MAP {'k1': NULL} should be coerced to the value type of the other rows in the VALUES list (Int64 in this case), so the CREATE TABLE succeeds with a Map(Utf8, Int64) column type where the second row has a NULL value.
Additional context
No response
Activity
Udaytaneja commentedon Jul 11, 2026
Hi mantainers , I'd like to work on this . Please assign this to me.
PG1204 commentedon Jul 11, 2026
Hi @Udaytaneja , since this is a direct follow up of #23406 which I worked on, is it alright with you if I take this one?
Udaytaneja commentedon Jul 11, 2026
Please if possible assign this to me , actually I was a bit interested in this one .
PG1204 commentedon Jul 11, 2026
Maybe you can take on another issue for now, or if this issue ends having a follow up, then you can take the next one? I shall tag you in it.
Udaytaneja commentedon Jul 11, 2026
Okk , but do tag me in the next one please
PG1204 commentedon Jul 11, 2026
take
test: assert coerced Map value type is Int64 for the apache#23474 rep…
fix: support type coercion for MAP literals with NULL values in VALUE…
fix: support type coercion for MAP literals with NULL values in VALUE…