根节点是MongoDB从中派生结果集的最后阶段。 阶段操作描述,例: COLLSCAN 集合扫描 IXSCAN 索引扫描 FETCH 检出文档 SHARD_MERGE 合并分片中结果 SHARDING_FILTER 分片中过滤掉孤立文档 LIMIT 使用limit 限制返回数 PROJECTION 使用skip 进行跳过 IDHACK 针对_id进行查询 COUNT 利用db
For example, you might find this recorded webinar MongoDB Sharding 101 by my colleague Adamo Tonete to be useful. Or perhaps Tim Vaillancourt’s MongoDB backup and recovery field guide would provide some useful information. If you want to catch our webinars as they happen, please subscribe...
To support hash-based sharding, MongoDB provides a hashed index type, which indexes the hash of the value of a field. These indexes have a more random distribution of values along with their range, but only support equality matches and cannot support range-based queries. Index Properties Unique...
SORT Sorted in memory LIMIT Use limit to limit the number of returns SKIP Use skip to skip IDHACK Query _id SHARDING_FILTER Query sharded data through mongos COUNTSCAN The stage returns when count does not use Index for count COUNT_SCAN The stage returns when count uses Index for count SU...
As discussed in a previous post onindexingin MongoDB, we can use the explain() method to learn about the selected query plan. This allows for an examination of the performance of a given query. It can be used in the following manner: ...