How does "Use MERGE for De-duplication of final tables" work in Snowflake destination?

[hongbo-miao]

I am trying to understand how "Use MERGE for De-duplication of final tables" works in Snowflake desitination.

If source data before is

A 1
B 2

and changed to

A 100
C 300

And this stream is using "Incremental| Append + Deduped".

Here is my understnading:

When "Use MERGE for De-duplication of final tables" is disabled, the Snowflake destination will change to

A 100
B 2
C 300

When "Use MERGE for De-duplication of final tables" is enabled, will the Snowflake destination will change to

A 100
C 300

Am I understanding correctly? Thanks!

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UPDATE 1:

Hmm I may be wrong. I saw source code.

When "Use MERGE for De-duplication of final tables" disabled, it calls insertRecordsDedupe. Inside insertRecordsDedupe, it calls cdcDeletes. So I assume it also deletes data.

Hmm so now I am not fully sure about their difference.