[hibernate-issues] [JIRA] (HHH-13879) Slow query log should use System#nanoTime not System#currentTimeMillis

[Sanne Grinovero (JIRA)]

Sanne Grinovero ( https://hibernate.atlassian.net/secure/ViewProfile.jspa?accountId=557058%3A99e61e65-956b-4a21-b29c-06057642e9ea ) *commented* on HHH-13879 ( https://hibernate.atlassian.net/browse/HHH-13879?atlOrigin=eyJpIjoiMDRiNGNkZTdkMDA0NGQ1NThkMmFkNWFhYWEzZGQzYmUiLCJwIjoiaiJ9 )

Re: Slow query log should use System#nanoTime not System#currentTimeMillis ( https://hibernate.atlassian.net/browse/HHH-13879?atlOrigin=eyJpIjoiMDRiNGNkZTdkMDA0NGQ1NThkMmFkNWFhYWEzZGQzYmUiLCJwIjoiaiJ9 )

hi Vlad, careful that’s not a straight forward change. I’m aware that  {{ currentTimeMillis }} isn't recommended, but using  {{ nanoTime }} might be a worse choice: it is bound to the time of the specific CPU core, so if the context is switched to a different CPU while performing the measured operation, the measured delta could be completely wrong - including possibly negative times as you’re also affected by different speeds of each core and complex power management of modern OSs.

The problem is that the task “running a query” is a blocking IO operation by nature, so we’re almost sure that the task will be re-scheduled - we’re just not sure on which physical CPU it will end up with.

Using `System#currentTimeMillis` is less precise, but all considered is possibly more suitable in this context.

Neither of them has the precision we would need for a “fast operation”, but the specific need of logging *slow queries* the milliseconds should be a good fit. At least while not super precise, it won’t be producing confusing results.

( https://hibernate.atlassian.net/browse/HHH-13879#add-comment?atlOrigin=eyJpIjoiMDRiNGNkZTdkMDA0NGQ1NThkMmFkNWFhYWEzZGQzYmUiLCJwIjoiaiJ9 ) Add Comment ( https://hibernate.atlassian.net/browse/HHH-13879#add-comment?atlOrigin=eyJpIjoiMDRiNGNkZTdkMDA0NGQ1NThkMmFkNWFhYWEzZGQzYmUiLCJwIjoiaiJ9 )

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