A mapping that reads a Deduplication transformation may take a long time to run because of the number of data comparisons that the transformation must perform. The number of comparisons relates to the number of input fields that the transformation must analyze.
The following table shows the number of calculations that a mapping performs for different numbers of data values on a single field:
Number of data values
Number of comparisons
To reduce the time that the mapping takes to run, the transformation can organize the input records into groups. A group is a set of records that contain identical values on a field that you specify. When you perform duplicate analysis on grouped data, the transformation analyzes the field data on the records within each group. The transformation does not compare the records in one group with the records in another group. The groups reduce the overall number of comparisons that the transformation must perform without any meaningful loss of accuracy in the mapping analysis.
Consider the following rules and guidelines when you organize data into groups:
The field on which you group the data is the
. Find the field on the
tab in the transformation. A group key field must contain a predictable range of expected duplicate values, such as a city name or a state name in an address data set.
The presence of duplicate values in the group key field does not mean that the respective input records must also be duplicates.
Do not specify a group key field that the asset requires to identify the identity information in the input data.
Groups do not reorder the position of the records in the mapping data set.