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  1. MariaDB Server
  2. MDEV-22224

Support JSON Path negative index

Details

    Description

      JSON Path allows to specify a negative array index, eg $[-1] returns the last element. This is not supported in MariaDB.

      Because of this, I believe there is no way to retrieve the last element without knowing the array length, nor to insert (JSON_ARRAY_INSERT()) an element at the end of the array. If I'm correct, this is a major missing feature for those who use JSON functions.

      MariaDB [test]> SELECT JSON_EXTRACT(JSON_ARRAY(1, 2, 3), '$[-1]');
      		 
      +--------------------------------------------+
      		 
      | JSON_EXTRACT(JSON_ARRAY(1, 2, 3), '$[-1]') |
      		 
      +--------------------------------------------+
      		 
      | NULL                                       |
      		 
      +--------------------------------------------+
      		 
      1 row in set, 1 warning (0.000 sec)
      		 
       
      		 
      Warning (Code 4042): Syntax error in JSON path in argument 2 to function 'json_extract' at position 3

      UPDATE: The task includes adding the negative index and the new keyword "last"

      Attachments

        Issue Links

          causes

          Bug - A problem which impairs or prevents the functions of the product. MDEV-28319 Assertion `cur_step->type & JSON_PATH_KEY' failed in json_find_path

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-29381 JSON paths containing dashes are reported as syntax errors in procedures

          • Critical - Crashes, loss of data, severe memory leak.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-29586 JSON_VALUE and JSON_EXTRACT doesn't handle special characters

          • Major - Major loss of function.
          • Closed
          is part of

          Task - A task that needs to be done. MDEV-28112 prepare 10.9.0 preview releases

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-27972 Unexpected behavior with negative zero (-0) in JSON Path

          • Major - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. MDEV-28350 Test failing on buildbot with UBSAN

          • Blocker - Blocks development and/or testing work, production could not run.
          • Closed

          Activity

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            View 6 older comments
            holyfoot Alexey Botchkov added a comment -

            Patch modification was discussed on slack.

            holyfoot Alexey Botchkov added a comment - Patch modification was discussed on slack.
            holyfoot Alexey Botchkov added a comment -

            ok to push

            holyfoot Alexey Botchkov added a comment - ok to push
            lstartseva Lena Startseva added a comment -

            Testing done

            lstartseva Lena Startseva added a comment - Testing done
            CRC Steven Haigh added a comment - - edited

            I'm trying to track back a regression that MIGHT end up being related to this.

            Given the following query:

            SELECT JSON_EXTRACT('{ "temperatures": { "AO-therm": "value" } }', '$.temperatures.AO-therm');

            The results for different versions of MariaDB are as follows:

            • 10.11-rc --> null
            • 10.10.4 --> null
            • 10.9.4 --> null
            • 10.8.6 --> "value"

            As such, this seems like a regression in behaviours from 10.8.6 onwards.

            CRC Steven Haigh added a comment - - edited I'm trying to track back a regression that MIGHT end up being related to this. Given the following query: SELECT JSON_EXTRACT( '{ "temperatures": { "AO-therm": "value" } }' , '$.temperatures.AO-therm' ); The results for different versions of MariaDB are as follows: 10.11-rc --> null 10.10.4 --> null 10.9.4 --> null 10.8.6 --> "value" As such, this seems like a regression in behaviours from 10.8.6 onwards.
            serg Sergei Golubchik added a comment -

            Yes, it is. See "causes" links above.

            serg Sergei Golubchik added a comment - Yes, it is. See "causes" links above.

            People

              rucha174 Rucha Deodhar
              f_razzoli Federico Razzoli
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              Dates

                Created:
                Updated:
                Resolved:

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