How Does Hashing Happens In Teradata?

1.	How Does Hashing Happens In Teradata?
Answer» Hashing is the mechanism through which data is distributed and retrieved to/from AMPs. Primary Index (PI) value of a ROW is the input to the Hashing Algorithm. Row Hash (32-bit number) value is the output from this Algorithm. Table Id + Row Hash is used to locate CYLINDER and Data block. Same Primary Index value and data TYPE will always produce same hash value. Rows with the same hash value will go to the same AMP. So data distribution depends directly on the Row Hash uniqueness; be careful while Choosing INDEXES in Teradata.

Answer»

Hashing is the mechanism through which data is distributed and retrieved to/from AMPs.
Primary Index (PI) value of a ROW is the input to the Hashing Algorithm.
Row Hash (32-bit number) value is the output from this Algorithm.
Table Id + Row Hash is used to locate CYLINDER and Data block.
Same Primary Index value and data TYPE will always produce same hash value.
Rows with the same hash value will go to the same AMP. So data distribution depends directly on the Row Hash uniqueness; be careful while Choosing INDEXES in Teradata.

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