[
https://issues.apache.org/jira/browse/DERBY-3882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12634598#action_12634598
]
Knut Anders Hatlen commented on DERBY-3882:
-------------------------------------------
The network server always sets the cursor name since it doesn't know if the
client has set a cursor name or not. If we had a way in DRDA to tell the server
that the client has called Statement.setCursorName(), the server didn't have to
set the cursor name in the normal case, and the lookup method wouldn't be
called. 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.
> 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.
--
This message is automatically generated by JIRA.
-
You can reply to this email to add a comment to the issue online.
