Because the Vantage architecture is massively parallel, it requires an efficient method for distributing and retrieving its data—hashing.
Vantage uses hashing to distribute data for tables with a PI to disk storage and uses indexes to access the data. Most indexes are based on row hash values rather than table column values.
For PIs, Vantage obtains a row hash by hashing the values of the PI columns. The row hash and a sequence number, which is assigned to distinguish between rows with the same row hash within a table, are called a row identifier, and uniquely identify each row in a table. The row identifiers for partitioned tables include a partition identifier. For more information on partitioned tables, see Partitioned Tables.
For SIs, Vantage computes a hash value using the hash of the values of the SI columns. Vantage uses this value when the SQL specifies an SI value. The SI subtable records the hash value for the SI, the actual value of the index columns (for synonym resolution), and a list of primary index row identifiers for the table being indexed.