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https://issues.apache.org/jira/browse/DERBY-6216?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13661385#comment-13661385
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Bryan Pendleton commented on DERBY-6216:
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I think that the basic idea was: in XPLAIN-only mode, the execution logic would
simply not open the tables. The "get" methods would immediately return "EOF";
the "update" methods would immediately return "SUCCESS". Nothing would
actually happen to the actual tables, but the execution tree of result set nodes
would be constructed and executed; it would simply complete instantly.
Hopefully it's actually not much code.
But the fact that we get a "ResultSet Not open" clearly indicates that at least
some of the execution ResultSet nodes would need to be changed to plant
"if XPLAIN-only mode, return EOF" logic into them.
> 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: 10.6.2.3, 10.7.1.4, 10.8.3.1, 10.9.1.0
> Environment: Solaris 10, MacOS X 10.6, Windows XP
> Reporter: Brett Bergquist
> Labels: features
>
> 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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