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  1. MariaDB Server
  2. MDEV-27036

Json_writer allows one to create duplicate object members

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    Details

    • Type: Bug
    • Status: Closed (View Workflow)
    • Priority: Major
    • Resolution: Fixed
    • Affects Version/s: 10.4
    • Fix Version/s: 10.8.0
    • Component/s: Optimizer
    • Labels:
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      Description

      Json_writer code allows one to write multiple members with the same name in a JSON object.

      This is likely to prevent proper processing of the created document.

      The most striking example is EXPLAIN FORMAT=JSON:

      {
        "query_block": {
          "select_id": 1,
          "table": {
            "table_name": "table",
            ...
          },
           "table": {
            ...
      

      The solution has two parts:

      Part #1: Follow the MDEV-23766 approach and make debug build generate assertion failures.

      Part #2: Fix EXPLAIN FORMAT=JSON code to not produce such invalid (or valid but not processable) JSON output.

      As for which version to fix this in: The problem with EXPLAIN FORMAT=JSON output is present from the very early versions (10.1). However, the fix will cause a lot of changes in EXPLAIN FORMAT=JSON output (the changes will be dummy but they will be there). This may not be desirable for older versions. Because of that, for now I'm setting fixVersion to 10.8.

      A question to be resolved: how to modify EXPLAIN/ANALYZE to make them well-formed JSON? Should we wrap them into an array, like MySQL does or do something else?)

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              Assignee:
              sergei.krivonos Sergei Krivonos (Inactive)
              Reporter:
              psergei Sergei Petrunia
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                Updated:
                Resolved:

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