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  1. MariaDB Server
  2. MDEV-13756

Implement descending index: KEY (a DESC, b ASC)

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      Description

      MySQL 8.0 introduced support for descending indexes in WL#1074. This involved some changes in InnoDB and many in the optimizer.

      MariaDB and older versions of MySQL silently ignore the ASC/DESC attribute in KEY definitions. All index fields (KEY_PART) are sorted in ascending order.

      The Oracle database defines the NULLS FIRST and NULLS LAST attributes for the ORDER BY clause, but not for CREATE INDEX. The defaults are the exact opposite of InnoDB behaviour:

      NULLS LAST is the default for ascending order, and NULLS FIRST is the default for descending order.

      InnoDB in MariaDB and before MySQL 8.0 supports only ascending order, and it sorts NULLS FIRST, not NULLS LAST like the above quote suggests Oracle to do.

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          includes

          Task - A task that needs to be done. MDEV-26938 support descending indexes internally in InnoDB

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

          Task - A task that needs to be done. MDEV-26939 support descending indexes for simple ORDER BY

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

          Task - A task that needs to be done. MDEV-26996 Support descending indexes in the range optimizer

          • Major - Major loss of function.
          • Open
          relates to

          Bug - A problem which impairs or prevents the functions of the product. MDEV-23571 InnoDB does not raise a warning if ALTER TABLE index operations are optimized away

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Open

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              Assignee:
              psergei Sergei Petrunia
              Reporter:
              marko Marko Mäkelä
              Votes:
              23 Vote for this issue
              Watchers:
              17 Start watching this issue

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                Created:
                Updated:

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