Marko Mäkelä 439a7c994a MDEV-14051 'Undo log record is too big.' error occurring in very narrow range of string lengths ...

InnoDB was writing unnecessary information to the
update undo log records. Most notably, if an indexed column is updated,
the old value of the column would be logged twice: first as part of
the update vector, and then another time because it is an indexed column.

Because the InnoDB undo log record must fit in a single page,
this would cause unnecessary failure of certain updates.

Even after this fix, InnoDB still seems to be unnecessarily logging
indexed column values for non-updated columns. It seems that non-updated
secondary index columns only need to be logged when a PRIMARY KEY
column is updated. To reduce risk, we are not fixing this remaining flaw
in GA versions.

trx_undo_page_report_modify(): Log updated indexed columns only once.

2017-10-24 17:00:04 +03:00

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