The Primary Index is the only thing that determines where a row will reside and the hashing algorithm never lies. It is important that you understand this process. When a new row arrives into Teradata, the following steps occur:
Teradatas PE examines the Primary Index value of the row. Teradata takes that Primary Index value and runs it through a Hashing Algorithm. The output of the Hashing Algorithm (i.e., a formula) is a 32-bit Row Hash. The 32-bit Row Hash will perform two functions: 1. The 32-bit Row Hash will point to a certain spot on the Hash Map, which will indicate which AMP will hold the row. 2. The 32-bit Row Hash will always remain with the Row as part of a Row ID. Hashing is a mathematical process where an Index (UPI, NUPI) is converted into a 32- bit row hash value. The key to this hashing algorithm is the Primary Index. When this value is determined, the output of this 32-bit value is called the Row Hash.
The Hashing Algorithm will produce random, but consistent row hashes with an end goal to produce a 32-bit row hash.