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  1. MariaDB Server
  2. MDEV-18284

JSON casting using JSON_COMPACT doesn't always work with values from subqueries

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      Description

      Given this test data

      CREATE TABLE json_test (a JSON, b JSON);
       
      INSERT INTO json_test VALUES ("[1,2,3]", '{"a":"foo"}');
      

      I can observe the following behavior:

      MariaDB [bugs]> SELECT JSON_OBJECT("a", JSON_COMPACT(a)) FROM (SELECT * FROM json_test) AS json_test_values;
      +-----------------------------------+
      | JSON_OBJECT("a", JSON_COMPACT(a)) |
      +-----------------------------------+
      | {"a": [1,2,3]}                    |
      +-----------------------------------+
      

      MariaDB [bugs]> SELECT JSON_OBJECT("a", JSON_COMPACT(a), "b", b) FROM (SELECT * FROM json_test) AS json_test_values;
      +-------------------------------------------+
      | JSON_OBJECT("a", JSON_COMPACT(a), "b", b) |
      +-------------------------------------------+
      | {"a": "[1,2,3]", "b": "{\"a\":\"foo\"}"}  |
      +-------------------------------------------+
      

      MariaDB [bugs]> SELECT JSON_OBJECT("a", JSON_COMPACT(a), "b", JSON_COMPACT(b)) FROM (SELECT * FROM json_test) AS json_test_values;
      +---------------------------------------------------------+
      | JSON_OBJECT("a", JSON_COMPACT(a), "b", JSON_COMPACT(b)) |
      +---------------------------------------------------------+
      | {"a": [1,2,3], "b": {"a":"foo"}}                        |
      +---------------------------------------------------------+
      

      The output of `JSON_COMPACT(a)` is sometimes treated as JSON and sometimes as a plain string

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            Assignee:
            anel Anel Husakovic
            Reporter:
            pprkut Heinz Wiesinger
            Votes:
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              Dates

              Created:
              Updated:
              Resolved:

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