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  1. MariaDB Server
  2. MDEV-33094

row-by-row logging needs to be disabled for the online ALTER log application stage

Details

    Description

      Engine-independent online alter table (MDEV-16329) brings an extra data-modification stage to the COPY alter table – online log changes application.

      For the normal copy stage, the row-by-row logging was disabled in MDEV-11415. This can be extended to the online log application.

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          is caused by

          Task - A task that needs to be done. MDEV-16329 Engine-independent online ALTER TABLE

          • 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-33087 ALTER TABLE...ALGORITHM=COPY should build indexes more efficiently

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

          Bug - A problem which impairs or prevents the functions of the product. MDEV-11415 Remove excessive undo logging during ALTER TABLE…ALGORITHM=COPY

          • Major - Major loss of function.
          • Closed

          Activity

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            nikitamalyavin Nikita Malyavin added a comment -

            Row-by-row logging is enabled for CREATE...SELECT in select_create::prepare.
            But it's turned off for IGNORE and REPLACE

                if (thd->lex->duplicates == DUP_ERROR && !thd->lex->ignore)
            		 
                  table->file->extra(HA_EXTRA_BEGIN_ALTER_COPY);

            git show c411393a844becf91a560ac8e53ab04cb4fb9219

            		 
             
            		 
            commit c411393a844becf91a560ac8e53ab04cb4fb9219
            		 
            Author: Marko Mäkelä <marko.makela@mariadb.com>
            		 
            Date:   Thu Jan 28 15:26:53 2021 +0200
            		 
             
            		 
                MDEV-24715 Assertion !node->table->skip_alter_undo in CREATE...REPLACE SELECT
            		 
                
                In commit 3cef4f8f0fc88ae5bfae4603d8d600ec84cc70a9 (MDEV-515)
            		 
                we inadvertently broke CREATE TABLE...REPLACE SELECT statements
            		 
                by wrongly disabling row-level undo logging.
            		 
                
                select_create::prepare(): Only invoke extra(HA_EXTRA_BEGIN_ALTER_COPY)
            		 
                if no special treatment of duplicates is needed.

            REPLACE operation has a special treatment in comparison with UPDATE and DELETE – it needs row-grained logging to carefully rollback the failed row insertion inside the statement. In comparison, this would lead to a statement failure in INSERT/UPDATE/DELETE/CREATE...SELECT/ALTER TABLE.

            Online ALTER does not allow the replace behavior for the online log application (neither it does for the copy stage as of now), so it should be safe

            nikitamalyavin Nikita Malyavin added a comment - Row-by-row logging is enabled for CREATE...SELECT in select_create::prepare . But it's turned off for IGNORE and REPLACE if (thd->lex->duplicates == DUP_ERROR && !thd->lex->ignore) table->file->extra(HA_EXTRA_BEGIN_ALTER_COPY); git show c411393a844becf91a560ac8e53ab04cb4fb9219   commit c411393a844becf91a560ac8e53ab04cb4fb9219 Author: Marko Mäkelä <marko.makela@mariadb.com> Date: Thu Jan 28 15:26:53 2021 +0200   MDEV-24715 Assertion !node->table->skip_alter_undo in CREATE...REPLACE SELECT In commit 3cef4f8f0fc88ae5bfae4603d8d600ec84cc70a9 (MDEV-515) we inadvertently broke CREATE TABLE...REPLACE SELECT statements by wrongly disabling row-level undo logging. select_create::prepare(): Only invoke extra(HA_EXTRA_BEGIN_ALTER_COPY) if no special treatment of duplicates is needed. REPLACE operation has a special treatment in comparison with UPDATE and DELETE – it needs row-grained logging to carefully rollback the failed row insertion inside the statement. In comparison, this would lead to a statement failure in INSERT/UPDATE/DELETE/CREATE...SELECT/ALTER TABLE. Online ALTER does not allow the replace behavior for the online log application (neither it does for the copy stage as of now), so it should be safe
            marko Marko Mäkelä added a comment -

            The fixes of this and MDEV-33087 may conflict with each other. We would want to only disable the row-level undo logging on the being-altered table, but only enable the MDEV-24621 optimization for the initial copying stage.

            marko Marko Mäkelä added a comment - The fixes of this and MDEV-33087 may conflict with each other. We would want to only disable the row-level undo logging on the being-altered table, but only enable the MDEV-24621 optimization for the initial copying stage.

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              nikitamalyavin Nikita Malyavin
              nikitamalyavin Nikita Malyavin
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