[jira] [Updated] (DERBY-4462) Use System.nanoTime on JDK 1.5 and higher to get finer precision internal measurements

["Mamta A. Satoor (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/DERBY-4462?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Mamta A. Satoor updated DERBY-4462:
-----------------------------------

    Urgency: Normal
     Labels: derby_triage10_10  (was: )
    
> Use System.nanoTime on JDK 1.5 and higher to get finer precision internal measurements
> --------------------------------------------------------------------------------------
>
>                 Key: DERBY-4462
>                 URL: https://issues.apache.org/jira/browse/DERBY-4462
>             Project: Derby
>          Issue Type: Improvement
>          Components: SQL
>            Reporter: Bryan Pendleton
>            Priority: Minor
>              Labels: derby_triage10_10
>
> Derby uses System.currentTimeMillis() to compute the internal elapsed time of certain operations.
> For example, the parseTime, bindTime, optimizeTime, generateTime, and compileTime measurements
> that are computed by GenericStatement.prepMinion use this technique.
> System.currentTimeMillis is not terribly accurate, since it is only updated 60 times a second; this
> means that it doesn't give very good information about operations that take less than 16 milliseconds,
> and the compilation time of a SQL statement is often shorter than that.
> As Knut Anders observes, we could use System.nanoTime, which is available in JDK 1.5 and above,
> to make more precise measurements.
> See DERBY-4297 for some related observations.

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