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hash

The hash function returns a hash value for the input value.

Syntax
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    hash( Source, Mod )

Arguments
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  • Source: The value to be hashed.
  • Mod: An optional modulo value to be applied to the hash result, so that the output value is between 0 and Mod - 1.

Returns
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The hash value of Source. If Mod is specified, the function returns the hash value modulo the value of Mod.

Examples
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  • hash("World") returns as 1846988464401551951
  • hash("World", 100) returns as 51 (1846988464401551951 % 100)
  • hash(datetime("2015-01-01")) returns as 1380966698541616202

Sampling
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You can use the hash function for sampling data if the values in one of its columns are uniformly distributed. In the following example, StartTime values are uniformly distributed and the function is used to run a query on 10% of the data.

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