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https://issues.apache.org/jira/browse/NIFI-15628?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Richard Scott updated NIFI-15628:
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Fix Version/s: 2.9.0
> Add Expression Language function unique(delimiter) to return unique delimited
> values
> ------------------------------------------------------------------------------------
>
> Key: NIFI-15628
> URL: https://issues.apache.org/jira/browse/NIFI-15628
> Project: Apache NiFi
> Issue Type: Improvement
> Components: NiFi API
> Reporter: Richard Scott
> Priority: Minor
> Fix For: 2.9.0
>
>
> This function returns the *unique values* from a {*}delimited string{*},
> {*}preserving the order of first occurrence{*}. The function takes a
> delimiter argument, splits the subject string on that delimiter, removes
> duplicate tokens while keeping the first occurrence, and joins the remaining
> tokens using the same delimiter.
> *Subject Type:* String
> *Arguments:*
> * {{delimiter}} (String): delimiter used to split and join the subject string
> *Return Type:* String
> h2. Use Case
> Many flows produce list-like attributes (e.g., tags, labels, realms, paths,
> routing hops) that accumulate duplicates as processing continues. A built-in
> function to deduplicate while preserving the original order improves
> readability, consistency, and downstream matching without requiring scripting.
> h2. Examples
> If the {{tags}} attribute has value:
> {{red,blue,red,green,blue,yellow}}
> ||Expression||Value||
> |{{{}$\{tags:unique(','){}}}}|{{red,blue,green,yellow}}|
> |{{{}$\{tags:unique(';'){}}}}|{{red,blue,red,green,blue,yellow}}|
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