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Coercion between floating point types and exact numeric types should result in floating point type as the common super type #14272

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findepi opened this issue Jan 24, 2025 · 0 comments · May be fixed by #14273
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findepi commented Jan 24, 2025

Describe the bug

When coercing decimal with other numeric types, the result is always decimal.
However, when one of operands is floating point, the result should be float.
Floating point's range of possible values cannot be fit into a decimal. Also NaN and Infinity cannot be converted to a decimal.

To Reproduce

> SELECT arrow_typeof(a) FROM (SELECT '1'::float UNION ALL SELECT '1'::decimal(10)) t(a);
+-------------------+
| arrow_typeof(t.a) |
+-------------------+
| Decimal128(17, 7) |
| Decimal128(17, 7) |
+-------------------+
> SELECT '1'::decimal(10,0) = '1e99'::float;
Arrow error: Cast error: Cannot cast to Decimal128(17, 7). Overflowing on inf

Expected behavior

PostgreSQL

postgres=# SELECT pg_typeof(a) FROM (SELECT '1'::float UNION ALL SELECT '1'::decimal(10)) t(a);
    pg_typeof
------------------
 double precision
 double precision
postgres=# SELECT '1'::decimal(10,0) = '1e99'::float;
 ?column?
----------
 f

(Note: PostgreSQL's decimal can express NaN and Infinity)

Additional context

No response

@findepi findepi added the bug Something isn't working label Jan 24, 2025
@findepi findepi linked a pull request Jan 24, 2025 that will close this issue
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