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  1. MariaDB Server
  2. MDEV-27776

Make EXPLAIN show filtered and partitions columns

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    Description

      MDEV-10000 adds EXPLAIN FOR CONNECTION for compatibility with MySQL-8.

      In MySQL-8, EXPLAIN FOR CONNECTION produces filtered and partitions columns. This means that anybody using EXPLAIN FOR CONNECTION syntax will expect these columns.

      On the other hand, in MariaDB, regular EXPLAIN and SHOW EXPLAIN do not show the extra columns.

      How can we be consistent across all commands? The solution is to first do what MySQL 5.7 did:

      • make the EXPLAIN command produce partitions and filtered columns.
      • then, make SHOW EXPLAIN and EXPLAIN FOR CONNECTION produce them, too.

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            Things to check:

            • Do we need to mark EXPLAIN PARTITIONS and EXPLAIN EXTENDED as deprecated?
            • Should EXPLAIN produce the warning with rewritten query, like EXPLAIN EXTENDED currently does?
            psergei Sergei Petrunia added a comment - Things to check: Do we need to mark EXPLAIN PARTITIONS and EXPLAIN EXTENDED as deprecated? Should EXPLAIN produce the warning with rewritten query, like EXPLAIN EXTENDED currently does?
            oleg.smirnov Oleg Smirnov added a comment -

            Do you think it makes sense to implement this in the same bb-10.8-MDEV-10000 branch rather than in a new one?

            oleg.smirnov Oleg Smirnov added a comment - Do you think it makes sense to implement this in the same bb-10.8- MDEV-10000 branch rather than in a new one?

            oleg.smirnov, yes. Please implement this over bb-10.8-MDEV-10000 branch

            psergei Sergei Petrunia added a comment - oleg.smirnov , yes. Please implement this over bb-10.8- MDEV-10000 branch
            oleg.smirnov Oleg Smirnov added a comment -

            After discussion on today's call we came to decisions:

            • EXPLAIN SELECT prints "partitions", "filtered" columns and produces the warning with rewritten query
            • EXPLAIN EXTENDED and EXPLAIN PARTITIONS produce the same output as EXPLAIN SELECT
              and two warnings, the second warning is about EXPLAIN EXTENDED| PARTITIONS being deprecated (like MySQL 5.7 does)
            oleg.smirnov Oleg Smirnov added a comment - After discussion on today's call we came to decisions: EXPLAIN SELECT prints "partitions", "filtered" columns and produces the warning with rewritten query EXPLAIN EXTENDED and EXPLAIN PARTITIONS produce the same output as EXPLAIN SELECT and two warnings, the second warning is about EXPLAIN EXTENDED| PARTITIONS being deprecated (like MySQL 5.7 does)

            Automated message:
            ----------------------------
            Since this issue has not been updated since 6 weeks, it's time to move it back to Stalled.

            julien.fritsch Julien Fritsch added a comment - Automated message: ---------------------------- Since this issue has not been updated since 6 weeks, it's time to move it back to Stalled.
            JIraAutomate JiraAutomate added a comment -

            Automated message:
            ----------------------------
            Since this issue has not been updated since 6 weeks, it's time to move it back to Stalled.

            JIraAutomate JiraAutomate added a comment - Automated message: ---------------------------- Since this issue has not been updated since 6 weeks, it's time to move it back to Stalled.

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              psergei Sergei Petrunia
              psergei Sergei Petrunia
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