Xiao Li created SPARK-13380:
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Summary: Document Rand(seed) and Randn(seed) Return
Indeterministic Results When Data Partitions are not fixed
Key: SPARK-13380
URL: https://issues.apache.org/jira/browse/SPARK-13380
Project: Spark
Issue Type: Documentation
Components: SQL
Affects Versions: 2.0.0
Reporter: Xiao Li
Priority: Minor
rand and randn functions with a seed argument are commonly used. Based on the
common sense, the results of rand and randn should be deterministic if the seed
parameter value is provided. For example, in MS SQL Server, it also has a
function rand. Regarding the parameter seed, the description is like: Seed is
an integer expression (tinyint, smallint, or int) that gives the seed value. If
seed is not specified, the SQL Server Database Engine assigns a seed value at
random. For a specified seed value, the result returned is always the same.
Update: the current implementation is unable to generate deterministic results
when the partitions are not fixed. This PR documents this issue in the function
descriptions.
@jkbradley hit an issue and provided an example in the following JIRA:
https://issues.apache.org/jira/browse/SPARK-13333
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