Is currently learning mongo, wrote in the book each shard key with uniqueness,
Problem a: the shard key and block is a one-to-many relationship,
Also see the shard key can be set index also can be a composite index,
Problem two: it assumes that a set has n shard, n shard shard keys are the same,

CodePudding user response:

Is currently learning mongo, wrote in the book each shard key with uniqueness,
Problem a: the shard key and block is a one-to-many relationship,
- for a table can have only one shard key
Also see the shard key can be set index also can be a composite index,
Problem two: it assumes that a set has n shard, n shard shard keys are the same,
- only one subdivision of a table by key