[EP-tech] Virtual fields -when does the 'cost' of processing get triggered?

[J.Salter at leeds.ac.uk (John Salter)]

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Hi All,
I'm looking adding a 'virtualwithvalue' (https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbazaar.eprints.org%2F452%2F1%2Fplugins%2FEPrints%2FMetaField%2FVirtualwithvalue.pm&data=05%7C01%7Ceprints-tech%40ecs.soton.ac.uk%7Cfbcfcf413824405ce07d08dad37b35f3%7C4a5378f929f44d3ebe89669d03ada9d8%7C0%7C0%7C638054823378768261%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=WTWoMYaq%2Bypx2X18SPHFdss%2BwHea1MGYVzDXnXiqkCg%3D&reserved=0) field to my EPrints install that does a search of the EPrint history, finding the first record, and returning the datestamp for that history item (i.e. the date the EPrint was created).
https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgist.github.com%2Fjesusbagpuss%2F8b899eb0eb9b2b733eead25c6dfd5973&data=05%7C01%7Ceprints-tech%40ecs.soton.ac.uk%7Cfbcfcf413824405ce07d08dad37b35f3%7C4a5378f929f44d3ebe89669d03ada9d8%7C0%7C0%7C638054823378768261%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=BfLbc7nYba2lw3Kos5bpsM2QAXma13tXiWuky8MQTyw%3D&reserved=0

I was thinking about the processing overhead for this field, and wondered when the value is actually calculated. I guess it's one of these options:
- when the object is created in memory e.g. via an EPrints::DataObj::EPrint->new() call
- when the value is referenced e.g. $eprint->value( "virtualwithvalue_field" ) ;

If it's the first option, I should add the field to the EPrint dataobj as a non-virtual field, and calculate it once if the value is not set, and then store it.
If it's the second option, then the overhead is lower (although I might still want to do the above).

I could trace this through the system myself - but thought (hoped) that someone might know... :)

Cheers,
John

John Salter
https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Forcid.org%2F0000-0002-8611-8266&data=05%7C01%7Ceprints-tech%40ecs.soton.ac.uk%7Cfbcfcf413824405ce07d08dad37b35f3%7C4a5378f929f44d3ebe89669d03ada9d8%7C0%7C0%7C638054823378768261%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=uWuK1N2fSz2UjIxaipSnIzwkFqDkTW0DJ8jONMxEmQM%3D&reserved=0

White Rose Libraries Technical Officer
IT - Application Support (Research)
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