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https://issues.apache.org/jira/browse/NIFI-15737?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Richard Scott reassigned NIFI-15737:
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Assignee: Richard Scott
> UpdateAttribute: Add Sequential Evaluation Mode for Advanced Rules
> ------------------------------------------------------------------
>
> Key: NIFI-15737
> URL: https://issues.apache.org/jira/browse/NIFI-15737
> Project: Apache NiFi
> Issue Type: New Feature
> Reporter: Richard Scott
> Assignee: Richard Scott
> Priority: Minor
>
> h2. *Motivation*
> The *UpdateAttribute* processor Advanced UI evaluates all rules against the
> original set of FlowFile attributes. Attribute updates made by one rule are
> not visible to subsequent rules during the same evaluation.
> This limits support for {*}incremental or dependent transformations{*},
> requiring:
> * loopback patterns
> * multiple processors
> * complex Expression Language
> These approaches introduce unnecessary complexity and reduce flow readability
> for what is conceptually a single logical operation.
> h2. *Proposed Enhancement*
> Introduce an optional evaluation mode:
> *Sequential Evaluation*
> When enabled, Advanced rules are evaluated in configured order. If a rule’s
> condition matches, its updates are applied immediately and become visible to
> subsequent rules during the same FlowFile evaluation.
>
> h2. *Example Use Case*
> h3. Scenario: Aggregating a total from optional attributes
> Attributes:
> * {{room.rate}}
> * {{room.service}}
> * {{in.room.entertainment}}
> * {{late.checkout}} (optional)
> h3. Example
> Assume the following incoming attributes:
> Rule 1
> Condition: always true
> hotel.bill.total = 0
> Rule 2
> Condition: room.rate exists
> hotel.bill.total = ${hotel.bill.total:plus(${room.rate})}
> Rule 3
> Condition: room.service exists
> hotel.bill.total = ${hotel.bill.total:plus(${room.service})}
> Rule 4
> Condition: in.room.entertainment exists
> hotel.bill.total = ${hotel.bill.total:plus(${in.room.entertainment})}
> Rule 5
> Condition: late.checkout exists
> hotel.bill.total = ${hotel.bill.total:plus(${late.checkout})}
>
> Evaluation result:
>
> After Rule 1: hotel.bill.total = 0
> After Rule 2: hotel.bill.total = 200
> After Rule 3: hotel.bill.total = 235
> After Rule 4: hotel.bill.total = 250
> Rule 5 skipped because late.checkout does not exist
> Final hotel.bill.total = 250
> This enables a natural, incremental approach to attribute transformation
> within a single processor, eliminating the need for loopback patterns and
> significantly improving flow clarity and maintainability.
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