[Db-derby Wiki] Update of "OptimizerTracing" by RichardHillegas

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The "OptimizerTracing" page has been changed by RichardHillegas:
http://wiki.apache.org/db-derby/OptimizerTracing

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You can trace the optimizer's analysis, one statement at a time. Optimizer tracing is enabled by this command:

   {{{ call syscs_util.syscs_register_tool( 'optimizerTracing', true ); }}}

After enabling tracing, issue the query you want to trace. E.g.:

   {{{ select columnname from sys.systables t, sys.syscolumns c where t.tableid = c.referenceid and t.tablename = 'SYSROLES'; }}}

Finally, turn tracing off and dump the trace. By default, the trace is printed on standard out. However, you can also force the trace to go into a file. Here's how you disable tracing and print the trace on standard out...

   {{{ call syscs_util.syscs_register_tool( 'optimizerTracing', false ); }}}

...and here's how you disable tracing, printing the trace to the file z1.txt:

   {{{ call syscs_util.syscs_register_tool( 'optimizerTracing', false, 'z1.txt' ); }}}