Eugene Kosov a4b3970c6e MDEV-25951 MariaDB crash after ALTER TABLE convert to utf8mb4 ...

Bug happens when partially indexed CHAR or VARCHAR field in converted from
utf8mb3 to utf8mb4.

Fixing by relaxing assertions. For some time dict_index_t and dict_table_t
are becoming not synchronized. Namely, dict_index_t has a new prefix_len which
is a multiple of a user-provided length and charset->mbmaxlen. But
the table still have and old mbmaxlen and assertion fails. This happens only
during utf8mb3 -> utf8mb4 conversions and the magic number 4 comes from
utf8mb_4_.

At the end of ALTER TABLE (innobase_rename_or_enlarge_columns_cache())
dict_index_t and dict_table_t became synchronized
again and will stay so at all times. For, example, they will be synchronized
on table load and newly added assertion proves that.

2021-09-08 16:08:32 +06:00

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