Min/Max functions do not work for firstn() and lastn() aggregation

Min/Max functions do not work for firstn() and lastn() aggregation

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Article ID: KB0079223

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Updated On:

Products Versions
TIBCO Streaming 7.7

Description

I want to obtain the maximum or minimum last N values from a list in an aggregate context.  For example.. 
max(lastn(4, MyField))
..produces a typecheck error in Studio ("not a valid aggregate expression").

Issue/Introduction

Min/Max functions do not work for firstn() and lastn() aggregation

Resolution

These errors occur because max() and min() functions cannot accept lists as input arguments.  Instead, use maxelement().. 
maxelement(lastn(4, MyField))

 

Additional Information

For reference, our List-related functions are noted in the Help under StreamBase Home > StreamBase References > StreamBase Expression Language Functions > (sub-heading) Simple Functions: Lists:

https://docs.tibco.com/pub/sb-cep/7.7.3/doc/html/reference/expressions.html
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