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  1. MariaDB Server
  2. MDEV-41153

json_escape() omits the second \u in surrogate pairs for non-BMP characters

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    • Q4/2026 Server Development

    Description

      Test:

      SELECT JSON_SET(_latin1'{}', '$.x', _utf8mb4 0xF09F9880);
      		 
      JSON_SET(_latin1'{}', '$.x', _utf8mb4 0xF09F9880)
      		 
      NULL
      		 
      Warnings:
      		 
      Warning	4038	Syntax error in JSON text in argument 1 to function 'json_set' at position 12

      If we comment out json_nice:

      SELECT JSON_SET(_latin1'{}', '$.x', _utf8mb4 0xF09F9880);
      		 
      JSON_SET(_latin1'{}', '$.x', _utf8mb4 0xF09F9880)
      		 
      {"x":"\uD83DDE00"}

      Note "\uD83DDE00" whereas expected value is "\uD83D\uDE00".

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          duplicates

          Bug - A problem which impairs or prevents the functions of the product. MDEV-40769 A character outside the first Unicode plane is written as one escape carrying both UTF-16 units, so the document a JSON function produces is not JSON and the server rejects its own output

          • Major - Major loss of function.
          • Open

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              gkodinov Georgi Kodinov
              svoj Sergey Vojtovich
              Raghunandan Bhat Raghunandan Bhat
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