innodb_expand_fast_index_creation should be optional
The server-side functionality from innodb_
1. We promise the same behavior as compared to the upstream server unless Percona-specific features are explicitly enabled by corresponding options.
2. Fast index creation may actually be slower than the default method in some cases. (e.g. when the data fits in the buffer pool and the merge buffer is too small, see https:/
3. There are upstream server bugs that make fast index creation inefficient in even more cases, for example https:/
We should have an option controlling whether fast index creation is used, and it should be disabled by default.