ADF BC REST supports HTTP ETag to check for data consistency. This is common approach to implement caching and optimistic locking in REST. ADF BC REST relies on EO change indicator attribute, when change indicator attribute value is updated, new ETag is generated. All clients with previous ETag value should be prevented from updating data, without refreshing to the latest state. Read more - 22.9.1 Checking for Data Consistency When Updating ADF REST Resource Items. There are issues with data consistency check in ADF BC REST, hopefully it will be fixed in the future (read below).
To test data consistency check, enable discriminator attribute in EO. I have enabled Salary as discriminator. Each time when this attribute is changed, new ETag value will be generated and clients holding previous value will require to re-query:
GET with If-Non-Match use case (works)
Initially we don't know ETag attribute value, we can query with empty value in If-Non-Match header. Current ETag value for the row will be returned together with the data: Read the complete article here.
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