refineCollectionShardKey (database command数据库命令)

Index Considerations指数注意事项

• Index Existence索引存在

  An index that supports the command's specified key must exist prior to running the command.在运行命令之前，必须存在支持命令指定键的索引。

  A supporting index is an index that starts with the new shard key specification; i.e. the index prefix matches the new shard key specification. 支持索引是以新的分片键规范开头的索引；即，索引前缀与新的分片键规范相匹配。That is, to change the shard key to { x: 1, y: 1 } from { x: 1 }, and index that starts with { x: 1, y: 1 } must exist; e.g.也就是说，要将分片键从{x:1}更改为{ x: 1, y: 1 }，并且必须存在以{ x: 1, y: 1 }开头的索引；如。

  • { x: 1, y: 1 }
  • { x: 1, y: 1, a: 1, b: 1}

  Note

  • The supporting index cannot be a partial index.支持索引不能是部分索引。
  • The supporting index cannot be a sparse index.支持索引不能是稀疏索引。
  • If the collection uses a non-simple collation, the supporting index must specify { locale: "simple" } collation.如果集合使用非简单排序规则，则支持索引必须指定{ locale: "simple" }排序规则。

• Unique Index唯一索引

  If the current shard index has a uniqueness constraint, the new shard key index must also have a unique constraint.如果当前分片索引具有唯一性约束，则新的分片键索引也必须具有唯一性限制。

  After creating the unique index to support the new shard key, drop the old shard key index before running refineCollectionShardKey.创建支持新分片键的唯一索引后，在运行refineCollectionShardKey之前删除旧分片键索引。

  Also, if the current shard index has a unique constraint, then the new shard key cannot specify "hashed" for any of its fields.此外，如果当前分片索引具有唯一约束，则新的分片键不能为其任何字段指定"hashed"。

  See also Sharded Collection and Unique Indexes.另请参见分片集合和唯一索引。

• Index Collation索引排序

  If the sharded collection has a non-simple default collation, then the index must include a collation document with { locale : "simple" }. 如果分片集合具有非简单的默认排序规则，则索引必须包含一个具有{locale:“simple”}的排序规则文档。At least one of the indexes whose fields support the shard key pattern must have the simple collation.字段支持分片键模式的索引中，至少有一个必须具有简单的排序规则。

Collection with non-simple Collation非简单排序集合

To set up the example in the test database:要在test数据库中设置示例，请执行以下操作：

1. Create the cafés collection in the test database, specifying French fr as the default collation.在test数据库中创建cafés集合，将法语fr指定为默认排序规则。

   db.getSiblingDB("test").createCollection( "cafés", { collation: { locale: "fr" } } );

2. Shard the collection using customer_id field as the initial shard key. 使用customer_id字段作为初始分片键对集合进行分片。Because the collection has a default fr collation and not a simple collation, the shardCollection command must include a collation: { locale: "simple" } option:因为集合具有默认的fr排序规则而不是简单的排序规则，所以shardCollection命令必须包含collation: { locale: "simple" }选项：

   db.adminCommand( {
      shardCollection: "test.cafés",
      key: { customer_id: 1 },
      collation: { locale: "simple" }
   } )

To modify the shard key to be both the customer_id field and the order_id field { customer_id: 1, order_id: 1 },要将分片键修改为customer_id字段和order_id字段{ customer_id: 1, order_id: 1 }，

1. Create the index to support the new shard key if the index does not already exist. Because the collection uses a non-simple collation, the index must include the collation: { locale: "simple" } option.如果索引不存在，则创建索引以支持新的分片键。因为集合使用非简单排序规则，所以索引必须包含collation: { locale: "simple" }选项。

   db.getSiblingDB("test").cafés.createIndex(
      { customer_id: 1, order_id: 1 },
      { collation: { locale: "simple" } }
   )

2. Run refineCollectionShardKey command to add the order_id field as a suffix:运行refineCollectionShardKey命令，将order_id字段添加为后缀：

   db.adminCommand( {
      refineCollectionShardKey: "test.cafés",
      key: { customer_id: 1, order_id: 1 }
   } )

Upon successful completion of the command, the shard key for the collection has changed to { customer_id: 1, order_id: 1 }. To verify, you can run sh.status().成功完成命令后，集合的分片键已更改为{customer_id:1，order_id:1}。要验证，可以运行shstatus()。