Defining a blocking key
About this task
Defining a blocking key is not mandatory but strongly advisable. Using a blocking key to partition data in blocks reduces the number of records that need to be examined as comparisons are restricted to record pairs within each block. Using blocking columns is very useful when you are processing a big dataset.
Procedure
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From the Blocking key menu, click
in the Blocking algorithm section.
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Click the name of the columns you want to use to partition the processed data in
blocks.
You can define more than one column in the table, but only one blocking key will be generated and listed in the BLOCK_KEY column in the Data table.For example, if you use an algorithm on the country and lnamecolumns to process records that have the same first character, data records that have the same first letter in the country and last names are grouped together in the same block. Comparison is restricted to record within each block.To remove a column from the Blocking key table, right-click it and select Delete or click on its name in the Data table.