hash()hash()

返回输入值的哈希值。Returns a hash value for the input value.

语法Syntax

hash(source [, mod ])hash(source [, mod ])

参数Arguments

  • source ：要进行哈希处理的值。source : The value to be hashed.
  • mod：一个可选模块值，在应用于哈希结果后输出值将在 0 到 mod - 1 之间mod : An optional module value to be applied to the hash result, so that the output value is between 0 and mod - 1

返回Returns

给定标量的哈希值，对给定 mod 值（如果已指定）取模。The hash value of the given scalar, modulo the given mod value (if specified).

警告

用于计算哈希的算法是 xxhash。The algorithm used to calculate the hash is xxhash. 此算法将来可能会更改，唯一的保证是：在单个查询中，对这个方法的所有调用都使用相同的算法。This algorithm might change in the future, and the only guarantee is that within a single query all invocations of this method use the same algorithm. 因此，建议不要将 hash() 的结果存储在表中。Consequently, you are advised not to store the results of hash() in a table. 如果需要持久化哈希值，请改用 hash_sha256() 或 hash_md5()。If persisting hash values is required, use hash_sha256() or hash_md5() instead. 请注意，计算这些函数比 hash() 更复杂。Note that these functions are more complex to calculate than hash()).

示例Examples

hash("World")                   // 1846988464401551951
hash("World", 100)              // 51 (1846988464401551951 % 100)
hash(datetime("2015-01-01"))    // 1380966698541616202

下面的示例使用哈希函数对 10% 的数据运行查询。假设值是均匀分布的（在本示例中，值为 StartTime 值），则使用哈希函数对数据采样很有帮助。The following example uses the hash function to run a query on 10% of the data, It is helpful to use the hash function for sampling the data when assuming the value is uniformly distributed (In this example StartTime value)

StormEvents 
| where hash(StartTime, 10) == 0
| summarize StormCount = count(), TypeOfStorms = dcount(EventType) by State 
| top 5 by StormCount desc