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MySQL error code

MySQL error 3906

MySQL server error 3906 is ER_EXCEEDED_MV_KEYS_SPACE, reported with SQLSTATE HY000.

Exceeded max total length of values per record for multi-valued index '%s' by %u bytes.
Error3906
NameER_EXCEEDED_MV_KEYS_SPACE
SQLSTATEHY000
GroupServer errors

Source: MySQL 8.4 Error Reference