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https://issues.apache.org/jira/browse/DERBY-3882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634916#action_12634916
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Dag H. Wanvik commented on DERBY-3882:
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> I haven't found any way to set the cursor name in the DRDA spec, but
> we always have the possibility to define a product-specific code
> point. Such a solution could also help us getting rid of the
> where-current-of rewrite in the client driver, which causes bugs like
> DERBY-1433.
This seems a good way to evolve this. It seems better to improve the
communication between the client and the server; this should help
reduce the need for special hacks on the client. On the downside, the
client would still need to older servers for a while, so it could take
some time to get rid of the old cruft.
> Expensive cursor name lookup in network server
> ----------------------------------------------
>
> Key: DERBY-3882
> URL: https://issues.apache.org/jira/browse/DERBY-3882
> Project: Derby
> Issue Type: Improvement
> Components: Network Server, Performance, SQL
> Affects Versions: 10.4.2.0
> Reporter: Knut Anders Hatlen
> Priority: Minor
>
> I have sometimes seen in a profiler that an unreasonably high amount of the
> CPU time is spent in
> GenericLanguageConnectionContext.lookupCursorActivation() when the network
> server is running. That method is used to check that there is no active
> statement in the current transaction with the same cursor name as the
> statement currently being executed, and it is normally only used if the
> executing statement has a cursor name. None of the client-side statements had
> a cursor name when I saw this.
> The method is always called when the network server executes a statement
> because the network server assigns a cursor name to each statement even if no
> cursor name has been set on the client side. If the list of open statements
> is short, the method is relatively cheap. If one uses
> ClientConnectionPoolDataSource with the JDBC statement cache, the list of
> open statements can however be quite long, and lookupCursorActivation() needs
> to spend a fair amount of time iterating over the list and comparing strings.
> The time spent looking for duplicate names in lookupCursorActivation() is
> actually wasted time when it is called from the network server, since the
> network server assigns unique names to the statements it executes, even when
> there are duplicate names on the client. It would be good if we could reduce
> the cost of this operation, or perhaps eliminate it completely when the
> client doesn't use cursor names.
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