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Version: 11.7.x

The Real-Time Updater violates unique keys

Problem

The Real-Time Updater violates unique keys on MongoDB. This usually happens when a combination of a delete and an insert ingestion message for the same record comes from the CDC, and the collection involved has a secondary unique index that differs from the primary key one.

Cause

The Real-Time Updater is designed to handle the case where a record is deleted and then inserted again with the same key. However, if the collection has a secondary unique index that differs from the primary key one, the RTU will violate the unique key constraint, causing the service to repeatedly restart.

Solution

Deactivate unique indexes on non-primary key fields for the projections. This will prevent the RTU from violating the unique key constraint.

note

If you are using the Projection Storer you should not encounter this issue.

How to deactivate unique indexes on non-primary key fields

  1. Go to the Projections page of the Fast Data section in the Console and select your System of Record.

  2. In the Projections list, select the projection you want to edit.

  3. In the Indexes section, click on the index tab that presents the unique constraint and deactivate the Unique checkbox.

Unique Keys Index deactivation