HASHAMP function in Teradata. In Teradata V1, the Access Module Processor (AMP) was the physical processing unit for all the Teradata database functions. Because Teradata Database hash functions are formally mature and mathematically sound, rows with unique primary indexes are always distributed in a uniformly random fashion across the AMPs, even when there is a natural clustering of key values. The HASHAMP function returns the identification number of the primary AMP for any Hash Bucket number. The SAMPLE clause is a Teradata extension to the ANSI SQL:2011 standard. Some SQL functions, referred to as niladic functions… This means that the requested rows are allocated across the AMPs as a function of the number of rows on each AMP. What is the function of an AMP? As can be seen it is a single-AMP retrieval and the optimizer is using the unique primary index to access the row. Each AMP then contained its own microprocessor, disk drive, file system, database software (Database Manager), Teradata Operating System (TOS), and YNET interface. Aggregate Functions Aggregate functions are typically used in arithmetic expressions. Aggregate functions operate on a group of rows and return a single numeric value in the result table for each group. 14. However AMP worker tasks that invoke the function will be held for the period of time that a table operator executes externally. Each AMP in Teradata has its own disk attached to it. It does output conversion and formatting C. It does the physical work associated with generating an answer set D. It develops the least expensive plan to return the requested response set ANS:: A,B,C. When no value is passed to the HASHAMP function, it returns a number that is one less than the number of AMPs in the current system configuration 1) First, we do a single-AMP RETRIEVE step from TDUSER.employee by way of the unique primary index "TDUSER.employee.EmployeeNo = 101" with no residual conditions. Also it performs any data conversion,aggregation,sorting,manipulate the disk sub system in the multi tasking and possibly parallel processing in the environment of the Teradata database. SQL Functions SQL functions return information about some aspect of the database, depending on the arguments specified at the time the function is invoked. Functions provide a single result by accepting input arguments and returning an output value. In that sense, each AMP was a node. Which feature is unique to Teradata? As mentioned previously, Teradata uses a hashing algorithm to determine which AMP is responsible for a data row's storage and retrieval. 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