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http://issues.apache.org/jira/browse/DERBY-1957?page=comments#action_12441664 ]
Knut Anders Hatlen commented on DERBY-1957:
-------------------------------------------
Daniel John Debrunner wrote this in a comment to DERBY-1876:
> I've thought in the past about having the common statistic
> information in a language ResultSet implementation that could wrap
> the real langugae ResultSet. Then the ResultSetFactory would return
> a instance of the real ResultSet wrapped with a StatisticsResultSet
> when timing etc. was enabled. The StatisticsResultSet would have
> code like:
>
> class StatisticsResultSet {
> private long openTime;
>
> private final ResultSet rs;
>
> pubic void openCore() {
> long s = System.currentTimeMillis();
> rs.openCore();
> long e = System.currentTimeMillis();
>
> openTime += (e -s);
> }
>
> This then removes the common fields and code to get the times from
> all the ResultSet classes, also leading to consistency.
>
> The issue with this that code that performs instanceof checks to get
> specific behaviour of a ResultSet no longer works, though there are
> solutions to that:
> A) Don't do it, it breaks the api in that the ResultSetFactory
> says it is returning a ResultSet, so that's all the callers
> should depend on.
> B) Follow the JBDC wrapper model, have a getRealResultSet() call
> in ResultSet api which would return this for most
> implementations, but the wrapped rs for
> StatisticsResultSet. Then code that needed to access the
> specific class would use the return from that method.
> Factor out run-time statistics information from language ResultSet classes
> --------------------------------------------------------------------------
>
> Key: DERBY-1957
> URL: http://issues.apache.org/jira/browse/DERBY-1957
> Project: Derby
> Issue Type: Improvement
> Components: SQL, Performance
> Reporter: Knut Anders Hatlen
> Priority: Minor
>
> The discussion in DERBY-1876 indicated that the performance of simple queries
> could be improved by factoring out run-time statistics information from the
> language ResultSet classes.
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