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- _hashBSONElement
_hashBSONElement¶
Description¶
- _hashBSONElement¶
2.4 新版功能.
An internal command that computes the MD5 hash of a BSON element. The _hashBSONElement command returns 8 bytes from the 16 byte MD5 hash.
The _hashBSONElement command has the following form:
db.runCommand({ _hashBSONElement: <key> , seed: <seed> })
The _hashBSONElement command has the following fields:
Field Type Description key BSONElement The BSON element to hash. seed integer A seed used when computing the hash. 注解
_hashBSONElement is an internal command that is not enabled by default. _hashBSONElement must be enabled by using --setParameter enableTestCommands=1 on the mongod command line. _hashBSONElement cannot be enabled during run-time.
Output¶
The _hashBSONElement command returns a document that holds the following fields:
- _hashBSONElement.key¶
The original BSON element.
- _hashBSONElement.seed¶
The seed used for the hash, defaults to 0.
- _hashBSONElement.out¶
The decimal result of the hash.
- _hashBSONElement.ok¶
Holds the 1 if the function returns successfully, and 0 if the operation encountered an error.
Example¶
Invoke a mongod instance with test commands enabled:
mongod --setParameter enableTestCommands=1
Run the following to compute the hash of an ISODate string:
db.runCommand({_hashBSONElement: ISODate("2013-02-12T22:12:57.211Z")})
The command returns the following document:
{
"key" : ISODate("2013-02-12T22:12:57.211Z"),
"seed" : 0,
"out" : NumberLong("-4185544074338741873"),
"ok" : 1
}
Run the following to hash the same ISODate string but this time to specify a seed value:
db.runCommand({_hashBSONElement: ISODate("2013-02-12T22:12:57.211Z"), seed:2013})
The command returns the following document:
{
"key" : ISODate("2013-02-12T22:12:57.211Z"),
"seed" : 2013,
"out" : NumberLong("7845924651247493302"),
"ok" : 1
}