NonStop SQL/MP Reference Manual

Table Of Contents
NonStop SQL/MP Reference Manual142115
D-50
Examples—DISPLAY STATISTICS
Estimated cost is a relative measure of cost derived using the same cost
functions that the SQL compiler uses to choose a query execution plan. The
estimate includes CPU, disk I/O, and message costs. Higher numbers tend to
indicate that SQL expects to process larger amounts of data. Large numbers are
not typically associated with fast on-line response times. Lower numbers imply
more efficient execution, but can be affected by missing or inaccurate statistics
or by skewed data distribution.
For more information about cost, see the NonStop SQL/MP Query Guide.
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Start Time, End Time, Elapsed Time, and Master Executor Execution Time
Master Executor Execution time is the amount of CPU time used by the SQL
executor. Elapsed time includes the execution time, I/O time, and the time used
to display the result.
°
Number of records accessed and number of records used
Records accessed is the number of rows read (including rows that do not satisfy
the selection criteria). Rows are counted for each table, underlying table of a
protection view, and temporary table. If you join a table to itself, separate
statistics are reported for each instance of the table. The number of rows
accessed in an index is not reported.
Records accessed does not indicate the specific number of physical disk reads or
writes because SQL uses disk caching to reduce the number of physical read and
write operations.
Records used is the number of rows that satisfy the query.
°
Number of disk reads
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Message count
Message count is usually the number of blocks passed from the disk process to
the file system. Sometimes an additional message is needed to ensure that the
last row was processed.
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Message bytes
Message bytes is the total amount of data transferred.
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Lock
Lock contains information about lock escalation.
ExamplesDISPLAY STATISTICS
Suppose that the last DML command was the following:
>> DELETE FROM I.P
+> WHERE SUPPNUM NOT IN (SELECT SUPPNUM FROM I.S
+> WHERE STATE = "TEXAS");
--- 41 row(s) deleted.