What is coalesce in Tranfrom map

[shaik_irfan]

What does index coalesce does in transform maps

[dravvyramlochun]

HI,

Configuring a target field to coalesce causes the import set to treat the field as a unique key. When selected, the import set application attempts to match source values to records with values from an existing record. If a match is found, the transform map updates the record instead of creating a new record. When false, the import set application always creates new records for each transformation. If multiple fields are set to coalesce, all coalesce values must match an existing record. If two fields are set for coalescing and a matching value is found for one of the coalescing fields but not on the other, a new record is inserted.

You must create an index on the target table if none of the coalesce fields are indexed, starting with the Fuji release. Indexing can improve performance for read and write operations. If one or more coalesce fields already has an index, you do not need to create an additional index. After setting the Coalesce value for all fields on the target table, use the Index Coalesce Fields related link to create an index. Before creating the index, ensure that the Coalesce value is set correctly for all fields on the target table to avoid creating unnecessary indexes for the same target table.

Reference:

http://wiki.servicenow.com/index.php?title=Creating_New_Transform_Maps#gsc.tab=0

http://wiki.servicenow.com/index.php?title=Using_the_Coalesce_Field#gsc.tab=0

Coalesce options

[Lucas Vieites]

Hi Shaik,

that related link is to create a database index on the fields on which you are coalescing the imported data.

This will improve the execution time of the import.

Kind regards,

Lucas Vieites

[dravvyramlochun · Accepted solution]

Another interesting article is Improve Import Set performance with the coalesce index feature in Fuji

If you   use the coalesce field without an index, your imports will be impacted, but not the target table.