XPLAIN reports negative EXECUTE_TIME for some parts of a join
-------------------------------------------------------------
Key: DERBY-4977
URL: https://issues.apache.org/jira/browse/DERBY-4977
Project: Derby
Issue Type: Bug
Components: SQL
Affects Versions: 10.7.1.1
Reporter: Knut Anders Hatlen
Priority: Minor
I see that if I execute a join against the system tables with XPLAIN and
statistics timing enabled, some of the rows in SYSXPLAIN_RESULTSET_TIMINGS have
negative values in the EXECUTE_TIME column.
Here are the contents of the SYSXPLAIN_RESULTSET_TIMINGS after two runs with
the attached repro script:
ij> select execute_time from my_schema.sysxplain_resultset_timings;
EXECUTE_TIME
--------------------
-1
0
0
-6
9
16
6 rows selected
ij> select execute_time from my_schema.sysxplain_resultset_timings;
EXECUTE_TIME
--------------------
-1
1
0
-7
10
15
6 rows selected
Note the two rows with negative values in both of the examples.
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