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From "Brett Bergquist (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (DERBY-6216) XPLAIN feature does not work and gives ERROR XCL16: ResultSet not open
Date Thu, 27 Feb 2014 19:23:23 GMT

    [ https://issues.apache.org/jira/browse/DERBY-6216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13914933#comment-13914933
] 

Brett Bergquist commented on DERBY-6216:
----------------------------------------

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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