Overview of the Issue

Unexpected type ENUM error when using SELECT DISTINCT on an enum column with a scatter query. Using GROUP BY instead of DISTINCT does not crash.

Reproduction Steps

vschema

{
  "sharded": true,
  "tables": {
    "example": {
      "column_vindexes": [
        {
          "column": "id",
          "name": "hash"
        }
      ]
    }
  },
  "vindexes": {
    "hash": {
      "type": "xxhash"
    }
  }
}

schema

CREATE TABLE `example` (
  `id` bigint unsigned NOT NULL,
  `foo` enum('a', 'b') NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci;

setup

INSERT INTO `example` (`id`, `foo`) VALUES (1, 'a'), (2, 'b');

error reproducer

SELECT DISTINCT `foo` FROM `example`;

Binary Version

vitess/vttestserver:v21.0.2-mysql80

Operating System and Environment details

vitess/vttestserver:v21.0.2-mysql80

Log Fragments