Does ES plan to allow changes to the "number of shard" when using snapshot recovery in the future?
Welcome to the community :)!
Parameters allowed to change during restore are described in the docs.
But
Some settings such as index.number_of_shards cannot be changed during the restore operation.
So no, you can't change the number of primary shards during a restore. You can change the number of replica shards as per the link above. To change the number of primary shards, after restore you'll have to do one of:
- reindex into a new index with the desired number of shards
- use the split Index API to increase the number of shards or the shrink Index API to reduce the number of shards