Hi David,
Trying to alter a table from number_of_shards
9 to 5 will results in
SQLParseException[Requested number of shards: <5> needs to be a factor of the current one: <9>]
Only 3 and 1 would be accepted in this case.
Take a look at How to decrease your number of shards in your cluster - Tutorials - CrateDB Community
for more details.
Thank you.