Rebuild & Compact

當你建立index時db.myCollection.ensureIndex({..}), mongo會馬上建立index

foreground (blocking)

• Default 預設的作法
• 因為是blocking, 在該document下, 無法進行任何query

background ()

• db.myCollection.ensureIndex({..},{background: true})
• index建立中依然可以read and wiite, 但是要等index建立完成才能使用該index
• 但是會花掉更多的時間

reIndex()

• 重建一個document內的indexes
• 非必要不會用到這個

The reIndex command drops all indexes on a collection and recreates them. This operation may be expensive for collections that have a large amount of data and/or a large number of indexes.

Documents - reIndex()

compact

• Rebuild collection
• blocking operation
• 可以 Make sure your collections storage are structurally optimized
• db.myCollection.runCommand({ compact: 'myCollection'})
• 需要去看你使用的Storage Engine, 是否需要這個操作

Rewrites and defragments all data and indexes in a collection. On WiredTiger databases, this command will release unneeded disk space to the operating system.

• Defragments documents
• Rebuild all indexes

Documents - compact