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https://issues.apache.org/jira/browse/DERBY-6216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13914933#comment-13914933
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Brett Bergquist commented on DERBY-6216:
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It really is a bug fix and not a feature. The documentation said the feature
was there in the earlier releases but they did not work and produced an error.
So no we have a fix with an intermittent test failure. I really don't think
it is any worse than it was before (not working at all) and as long as the
other tests run seem to be unaffected by this (other than the intermittent test
failure), I don't think the risk is too great.
The feature is extremely useful when trying to analyze performance of queries
where the is a very large amount of data to be processed. Without the feature,
I had to wait many hours (the query was running a bad plan) just to see that it
was choosing a bad plan.
Of course this is just my opinion :)
> XPLAIN feature does not work and gives ERROR XCL16: ResultSet not open
> ----------------------------------------------------------------------
>
> Key: DERBY-6216
> URL: https://issues.apache.org/jira/browse/DERBY-6216
> Project: Derby
> Issue Type: Bug
> Components: Tools
> Affects Versions: 10.6.2.4, 10.7.1.4, 10.8.3.3, 10.9.1.0
> Environment: Solaris 10, MacOS X 10.6, Windows XP
> Reporter: Brett Bergquist
> Assignee: Bryan Pendleton
> Labels: derby_triage10_11, features
> Fix For: 10.11.0.0
>
> Attachments: addTests.diff, emptyRS.diff, noMemberField.diff,
> preparedTests.diff, xplain-only.diff
>
>
> I am running Derby 10.9.1.0 and am trying to figure out a performance
> problem with query taking too long. I don’t actually want to run the query
> so from the documentation, I try:
> call syscs_util.syscs_set_runtimestatistics(1);
> call syscs_util.syscs_set_xplain_schema('STATS');
> call syscs_util.syscs_set_xplain_mode(1);
> --- my query here
> call syscs_util.syscs_set_runtimestatistics(0);
> call syscs_util.syscs_set_xplain_schema('');
> call syscs_util.syscs_set_xplain_mode(0);
> When it runs my query, I get:
> ERROR XCL16: ResultSet not open. Operation 'getMetaData' not permitted.
> Verify that autocommit is OFF.
> I try the following with IJ just to see:
> call syscs_util.syscs_set_runtimestatistics(1);
> call syscs_util.syscs_set_xplain_schema('STATS');
> call syscs_util.syscs_set_xplain_mode(1);
> select sql_text from syscs_diag.transaction_table where status != 'IDLE';
> call syscs_util.syscs_set_runtimestatistics(0);
> call syscs_util.syscs_set_xplain_schema('');
> call syscs_util.syscs_set_xplain_mode(0);
> Note I have tried this with real tables as apposed to the
> syscs_diag.transaction_table with the same result. The only reason that I
> posted this with this table is that it is a table that is accessible for any
> database.
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