Conditional Merges [REQUEST]

Is your feature request related to a problem? Please describe. When we ingest datatypes from different sources, we may run into the issue where we ingest data from an old source and one from a recent source with different properties. The current implementation builds a merge query which simply overwrites the properties on matched nodes based on which record was ingested first. I would like for there to be a way to conditionally change properties on a node.

Describe the solution you'd like When I create an interpretation within my pipeline, I would like to declare the following:

merge_condition: latest # Where we could have different options latest being greater value wins. default=None
condition_key: date_created # key of the value we are comparing with.
condition_value: !!python/jmespath date_created #The value from the record we are pulling from

This would then modify the merge query which currently performs the following for source nodes:

MERGE(node:$node_type) WHERE node.key = $key
ON CREATE
    SET node.param = param.value
ON MATCH
    SET node.param = param.value

I would like it to create the following:

MERGE(node:$node_type) WHERE node.key = $key
ON CREATE
    SET node.param = param.value
ON MATCH
    SET node.condition = CASE WHEN $condition THEN true ELSE false END // We need a variable for the condition in some way
    SET node.param = CASE WHEN node.condition THEN param.value ELSE node.param END
    // Find a way to unset node.condition

Where condition in our case would be (date_created > node.date_created)

Describe alternatives you've considered The alternative I can perform to ensure the recency of my data is I can schedule my pipelines such that the recent data comes in after the old data. In my pipeline, I can create an interpreter that makes a call to the database to get the value, then conditionally write to the database (this takes too long.)

Additional context

nodestream-proj / nodestream

Conditional Merges [REQUEST] #97