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https://issues.apache.org/jira/browse/NIFI-8161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17311562#comment-17311562
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Arek Burdach commented on NIFI-8161:
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[~exceptionfactory] [~turcsanyip] I've made changes in code as you both
suggested. What's the plan now? Should I finally rebase the change do main? Who
will pick it to merge and in which release it will land? I would like to add
some migration guide / release note for users that after this change, for some
corner cases, they should change format to be compatible with DateTimeFormatter
formats. Where can I place it?
> NiFi EL: migration from SimpleDateFormat to DateTimeFormatter
> -------------------------------------------------------------
>
> Key: NIFI-8161
> URL: https://issues.apache.org/jira/browse/NIFI-8161
> Project: Apache NiFi
> Issue Type: Improvement
> Reporter: Arek Burdach
> Assignee: Arek Burdach
> Priority: Major
> Labels: perfomance, pull-request-available
> Time Spent: 2h
> Remaining Estimate: 0h
>
> In NiFi Expression Language we are commonly using SimpleDateFormat. It is
> old, inefficient approach: due to mutability of SimpleDateFormat it need to
> be recreated for each operation. Also this format is lax in some places where
> user would like to be more strict. In my opinion better approach would be
> usage of java8 DateTimeFormatter instead.
> I've done some benchmarks that you can check on your own in
> FormatEvaluatorBenchmark. Results on my 8-core, i7-1065G7:
> - before change (SimpleDateFormat): 11.230 ± 5.407 us/op
> - after switching to DateTimeFormatter API: 4.747 ± 0.426 us/op
> - after introduction of preparation of formatter for literal formats: 2.025 ±
> 0.055 us/op
> This change is not 100% transparent so some changes might be necessary in
> users code. Most of differences are visible in modifications that I've made
> in TestQuery tests:
> - back tick (`) for escaping of extra characters is not supported anymore -
> only single quote is supported
> - "repeated" syntax like "dd" for days strictly check if two digits were
> provided - if someone need to use more lax syntax, need to use single "d"
> syntax
> [update]
> After switching to lenient mode, parsing is compatible with SimpleDateFormat
> in second point ("repeated" syntax)
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