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Change to innodb_large_prefix with respect to creating long indexes


Hi there,

We noticed a change between MariaDB 10.1.18 and 10.1.20, but I haven't been
able to find anything in the changelogs or JIRA that would help me
understand what changed, and why.

On 10.1.18, if I set `innodb_large_prefix=OFF` I can create indexes with
lengths greater than 767 bytes and MariaDB only issues a warning. If I
configure `innodb_large_prefix=ON` I get an error and the index fails to
create. This seems like a bug?

On 10.1.20, mysql fails to create the index regardless of how
innodb_large_prefix is configured.

We think that the result is that in 10.1.20, tables must be created or
altered to use `ROW_FORMAT DYNAMIC` or `ROW_FORMAT COMPRESSED` if they are
to contain an index with greater than 767 bytes in it.

Is this the desired behavior? Was there a bug in 10.1.18 (and maybe

I'm trying to understand the context better so that when devs ask us why
index creation is failing, we give them the correct answer for why it used
to work, and what they should be doing differently now that we're on


  Marco Nicosia
  Pivotal Software, Inc.

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