[I] Spark `negative` returns wrong results for decimal columns [datafusion]

["neilconway (via GitHub)" <gi...@apache.org>]

neilconway opened a new issue, #25942:
URL: https://github.com/apache/datafusion/issues/25942

   ### Describe the bug
   
   With the Spark functions enabled and ANSI mode off (the default), `negative()` on a decimal column either fails or returns wrong values. It works correctly on a decimal literal, and on a column when ANSI mode is on.
   
   ### To Reproduce
   
   Run with `datafusion-cli --spark`:
   
   ```sql
   CREATE TABLE t AS VALUES (CAST(1.23 AS DECIMAL(10,2))), (CAST(-4.50 AS DECIMAL(10,2)));
   
   SELECT negative(column1) FROM t;
   -- Arrow error: Invalid argument error: column types must match schema types, expected Decimal128(10, 2) but found Decimal128(38, 10) at column index 0
   
   SELECT CAST(negative(column1) AS DOUBLE) AS v FROM t;
   -- returns -1.23e-8 and 4.5e-8 (expected -1.23 and 4.5)
   
   -- Literal input: correct (-1.23)
   SELECT negative(CAST(1.23 AS DECIMAL(10,2)));
   
   -- ANSI mode: correct (-1.23, 4.50)
   SET datafusion.execution.enable_ansi_mode = true;
   SELECT negative(column1) FROM t;
   ```
   
   In a debug build, both column queries instead fail with `Internal error: Assertion failed: result_data_type == *expected_type: Function 'negative' returned value of type 'Decimal128(38, 10)' while the following type was promised at planning time and expected: 'Decimal128(10, 2)'`.
   
   `Decimal64` and `Decimal256` columns also give wrong values. For example, with the table above, `SELECT CAST(negative(arrow_cast(column1, 'Decimal64(10, 2)')) AS DOUBLE) FROM t` returns `-0.000123` and `0.00045`.
   
   ### Expected behavior
   
   `negative(column1)` returns `-1.23` and `4.50`, as it does for literals and in ANSI mode.
   
   ### Additional context
   
   Reproduced on `main` at commit 2b1fcae86, in both release and debug builds.
   
   *This bug report was generated by Claude.*
   


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Re: [I] Spark `negative` returns wrong results for decimal columns [datafusion]

["mattsu2020 (via GitHub)" <gi...@apache.org>]

mattsu2020 commented on issue #25942:
URL: https://github.com/apache/datafusion/issues/25942#issuecomment-5941607708

   take


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