As part of the research I did for the 2nd edition of our Exadata book I used session statistics quite heavily. Session statistics can provide additional insights in situations where the wait interface on its own doesn’t get you any further.
On the command line, my tools of choice are either Tanel Poder’s excellent Session Snapper or Adrian Billington’s mystats utility. There are of course others, it just so happened that I’ve been using the previous two quite heavily. If you prefer a graphical front-end such as SQL Developer, you can grab the change in session statistics easily as described in an earlier post.
I’m not sure why it never occurred to me to check if SQL Developer’s best friend, sqlcl, has the same functionality. Well it does, and that’s great news. The other great news is that you can download sqlcl directly from Oracle’s website now.
UPDATE when I first wrote about sqlcl‘s ability to display session statistics it had a problem getting the actual execution plan from the database (it used explain plan for <sql> internally. This is fixed with the current release. I updated the article accordingly.
Downloading SQLcl the new way
The first step to complete is to pull the latest version of sqlcl. Many thanks to Connor McDonald who told me there is a super-easy way to always get the latest version. Just use the following URL:
https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip
Great! I don’t even need to worry about the version:
$ wget https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip --2021-07-29 17:11:23-- https://download.oracle.com/otn_software/java/sqldeveloper/sqlcl-latest.zip Resolving download.oracle.com (download.oracle.com)... 104.76.200.85 Connecting to download.oracle.com (download.oracle.com)|104.76.200.85|:443... connected. HTTP request sent, awaiting response... 200 OK Length: 37581054 (36M) [application/zip] Saving to: ‘sqlcl-latest.zip’ sqlcl-latest.zip 100%[=====================================>] 35.84M 2.43MB/s in 18s 2021-07-29 17:11:42 (1.95 MB/s) - ‘sqlcl-latest.zip’ saved [37581054/37581054]
Note that I’m downloading sqlcl-latest.zip, which translates to 21.2.1.195.1252 at the time of writing:
$ cd sqlcl/bin && ./sql -V SQLcl: Release 21.2.1.0 Production Build: 21.2.1.195.1252
With the latest sqlcl release unzipped it’s time to grab some session statistics.
Session Statistics, please!
To keep matters reasonably simple I’m using a non-partitioned table for my demonstration. As always, my examples use the excellent Swingbench (Order Entry) benchmark schema. Once connected to the database, I can start investigating. By the way I’m running this query on Oracle 19c in a VM on my laptop.
The first step is to enable auto-trace as shown here:
SQL> show version
Oracle SQLDeveloper Command-Line (SQLcl) version: 21.2.1.0 build: 21.2.1.195.1252
SQL> help set autotrace
SET AUTOTRACE
SET AUTOT[RACE] {OFF|ON|TRACE[ONLY]}
SQL> set autotrace on
Autotrace Enabled
Shows the execution plan as well as statistics of the statement.
Let’s run a query against the orders table:
SQL> var oid number
SQL> exec :oid := 1
PL/SQL procedure successfully completed.
SQL> select /*+ gather_plan_statistics */ /* sqlcl is cool */
2* order_id, order_date, order_mode from soe.orders o where o.order_id = :oid;
ORDER_ID ORDER_DATE ORDER_MODE
___________ __________________________________ _____________
1 07-MAY-11 06.00.00.000000000 AM direct
PLAN_TABLE_OUTPUT
______________________________________________________________________________________________________________
SQL_ID f746puksv24jv, child number 0
-------------------------------------
select /*+ gather_plan_statistics */ /* sqlcl is cool */ order_id,
order_date, order_mode from soe.orders o where o.order_id = :oid
Plan hash value: 4043159647
-----------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows | A-Rows | A-Time | Buffers | Reads |
-----------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | 1 |00:00:00.01 | 4 | 3 |
| 1 | TABLE ACCESS BY INDEX ROWID| ORDERS | 1 | 1 | 1 |00:00:00.01 | 4 | 3 |
|* 2 | INDEX UNIQUE SCAN | ORDER_PK | 1 | 1 | 1 |00:00:00.01 | 3 | 2 |
-----------------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("O"."ORDER_ID"=:OID)
Statistics
-----------------------------------------------------------
1 CPU used by this session
1 CPU used when call started
1 DB time
44 Requests to/from client
44 SQL*Net roundtrips to/from client
3 buffer is not pinned count
1299 bytes received via SQL*Net from client
84726 bytes sent via SQL*Net to client
4 calls to get snapshot scn: kcmgss
4 calls to kcmgcs
24576 cell physical IO interconnect bytes
4 consistent gets
4 consistent gets examination
1 consistent gets examination (fastpath)
4 consistent gets from cache
1 enqueue releases
1 enqueue requests
4 execute count
195 file io wait time
3 free buffer requested
1 index fetch by key
32768 logical read bytes from cache
56 non-idle wait count
4 opened cursors cumulative
1 opened cursors current
4 parse count (total)
3 physical read IO requests
24576 physical read bytes
3 physical read total IO requests
24576 physical read total bytes
3 physical reads
3 physical reads cache
1 rows fetched via callback
4 session logical reads
3 shared hash latch upgrades - no wait
1 sorts (memory)
2010 sorts (rows)
1 table fetch by rowid
46 user calls
This is pretty nifty in my opinion. There’s an execution plan and a whole raft of relevant session statistics.
Unlike in earlier sqlcl releases the execution plan is now fetched from the database. I ran a sql trace to confirm although the presence of a SQL ID and a child number in the above output should indicate this is the “real” plan.
Happy Troubleshooting!
Martins Blog 