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- setFeatureCompatibilityVersion
setFeatureCompatibilityVersion¶
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Definition¶
- setFeatureCompatibilityVersion¶
3.4 新版功能.
Enables or disables MongoDB 3.4 features that persist data that are backwards-incompatible with MongoDB 3.2. You can only issue the setFeatureCompatibilityVersion against the admin database.
The command takes the following form:
db.adminCommand( { setFeatureCompatibilityVersion: <version> } )
where <version> can be:
- "3.4" to enable the backward incompatible features, or
- "3.2" to disable these features.
Behavior¶
Affected Features¶
The following 3.4 features persist data that earlier MongogDB versions cannot correctly handle and require that featureCompatibilityVersion be set to "3.4":
Index version v: 2. v:2 indexes add support for collation and decimal data type. Earlier index versions support neither collation nor the decimal data type.
If featureCompatibilityVersion: "3.4", indexes created in MongoDB 3.4 default to v: 2 . Otherwise, new indexes default to v: 1.
警告
Enabling these backwards-incompatible features can complicate the downgrade process. For details, see 删除 3.4 不兼容的功能.
It is recommended that after upgrading, you allow your deployment to run without enabling these features for a burn-in period to ensure the likelihood of downgrade is minimal. When you are confident that the likelihood of downgrade is minimal, enable these features.
Default Values¶
| 3.4 Deployments | featureCompatibilityVersion |
|---|---|
| For new deployments | "3.4" |
| For deployments upgraded from 3.2 | "3.2" until you setFeatureCompatibilityVersion to "3.4". |
Idempotency¶
This command must perform writes to an internal system collection. If for any reason the command does not complete successfully, you can safely retry the command as the operation is idempotent.
Examples¶
Enable 3.4 Backwards Incompatible Features¶
To enable the 3.4 backwards-incompatible features, run the setFeatureCompatibilityVersion command against the admin database:
注解
db.adminCommand( { setFeatureCompatibilityVersion: "3.4" } )
警告
Enabling these backwards-incompatible features can complicate the downgrade process. For details, see 删除 3.4 不兼容的功能.
It is recommended that after upgrading, you allow your deployment to run without enabling these features for a burn-in period to ensure the likelihood of downgrade is minimal. When you are confident that the likelihood of downgrade is minimal, enable these features.
Disable 3.4 Backwards Incompatible Features¶
To disable the 3.4 backwards-incompatible features, run the setFeatureCompatibilityVersion command against the admin database:
注解
db.adminCommand( { setFeatureCompatibilityVersion: "3.2" } )
Setting the featureCompatibilityVersion to "3.2 disables the use of these features and does not remove existing usage of these features.
If performed as part of a downgrade to 3.2 procedure, you must also manually remove the existing usage before downgrading the binaries. For details, see 删除 3.4 不兼容的功能.