On 6/17/13 8:51 AM, Knut Anders Hatlen wrote:
Rick Hillegas<[email protected]> writes:
I would like to use the PlanExporter tool to view a query plan in xml.
But I am having a hard time figuring out how to use this tool. The
documentation on PlanExporter is divided between a couple user guides,
and somehow, flipping back and forth between them, I have managed to
not understand how to operate the tool. Here is my attempt to get
xplain-style statistics for a query. As you can see, I can't locate
the stmt_id:
ij version 10.11
ij> connect 'jdbc:derby:db;create=true';
ij> call syscs_util.syscs_set_runtimestatistics(1);
0 rows inserted/updated/deleted
ij> call syscs_util.syscs_set_xplain_schema('MY_STATS');
0 rows inserted/updated/deleted
ij> select tablename from sys.systables where 1=2 order by tablename;
Does it work as expected if you remove the 1=2 predicate?
Aha. Yes, I get a statement id if I omit that predicate.
Thanks!
-Rick
The recording of the statistics happens in the close() method of the
top-level result set (see NoPutResultSetImpl.close()). If the top-level
result set is a ProjectRestrictResultSet, and there is a predicate that
is known at compile time to evaluate to false, it seems to take a
shortcut so that NoPutResultSetImpl.close() is not invoked:
/* Nothing to do if open was short circuited by false constant expression
*/
if (shortCircuitOpen)
{
isOpen = false;
shortCircuitOpen = false;
source.close();
return;
}
Notice that it doesn't call super.close() in this case. I suspect that
this is what's causing the issue you're seeing.
