[I] MIN/MAX fail with an internal error on RunEndEncoded columns [datafusion]

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

grevend opened a new issue, #26247:
URL: https://github.com/apache/datafusion/issues/26247

   ### Describe the bug
   
   `MIN` and `MAX` fail with an internal error when their argument is a `RunEndEncoded` column, both as aggregates (grouped or not) and as window functions. The same queries work on plain and `Dictionary`-encoded columns, and other aggregates such as `SUM` and `AVG` already accept `RunEndEncoded` input.
   
   ### To Reproduce
   
   In `datafusion-cli`:
   
   ```sql
   CREATE TABLE t AS SELECT arrow_cast(arrow_cast(column1, 'UInt32'),
     'RunEndEncoded("run_ends": non-null Int32, "values": UInt32)') AS v
   FROM (VALUES (1), (1), (3));
   
   SELECT max(v) FROM t;
   ```
   
   fails with:
   
   ```
   Internal error: Min/Max accumulator not implemented for type RunEndEncoded("run_ends": non-null Int32, "values": UInt32)
   ```
   
   ### Expected behavior
   
   `SELECT max(v) FROM t` returns `3` as `UInt32`, the same as it does for a `UInt32` or `Dictionary(Int32, UInt32)` column.
   
   ### Additional context
   
   `MIN`/`MAX` use a user-defined signature, so their argument type comes only from `get_min_max_result_type` in `datafusion/functions-aggregate/src/min_max.rs`. It unwraps `Dictionary` to its value type, which makes the planner insert a cast, but passes `RunEndEncoded` through unchanged, so the accumulator receives a type it has no implementation for.
   
   #24564 / #24565 added `RunEndEncoded` handling to `coerced_from`, but user-defined signatures don't go through that path, so it doesn't cover `MIN`/`MAX`.
   
   ### Willingness to contribute
   
   I plan to contribute a fix for this bug independently


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Re: [I] MIN/MAX fail with an internal error on RunEndEncoded columns [datafusion]

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

alamb closed issue #26247: MIN/MAX fail with an internal error on RunEndEncoded columns
URL: https://github.com/apache/datafusion/issues/26247


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