Thursday, January 07, 2016

Tuning SQL with Javascript in SQLCL

In case anyone missed it, #sqlcl has the ability to run javascript. This opens a lot of options.  Here's a simple example that shows how to using javascript.

  • Open a new Database Connection
  • Collect stats on the base connection
  • Do work on the main connection
  • Collect stats again
  • Only Print the stats that changed

In SQL Developer, the autotrace feature has for a long time selected the session statistics and display them.  Then you can diff those to another run and see what changes.  Jeff of course has blogs on this That's great but where's it leave a #sqlcl user? Enter JavaScript.

Here's the end result.  I ran a select count on all_objects filtered to DBA_%.  The things to notice is the Work Session's SID and Monitor Session's SID is different and printed to show I didn't cheat.  The command to execute is just passed as arguments to the script command.  The result is the count ran. I got the stats before and after.  Then it's just a simple loop comparing them to see what changed and print on the far right the actual difference.

The JavaSript is below and has comments enough to follow hopefully.  I'll post it to our #sqlcl github examples directory shortly.

// declare the 2 java files needed
var DriverManager = Java.type("java.sql.DriverManager");
var DBUtil  = Java.type("oracle.dbtools.db.DBUtil");

// Create a new connection to use for monitoring
var jdbc = conn.getMetaData().getURL();
var user = 'klrice';
var pass = 'klrice';
var conn2 = DriverManager.getConnection(jdbc,user,pass);
var util2 = DBUtil.getInstance(conn2);

// probably a better way to rpad a string
function pad(s,n){
   s = s.toString() + "                                                                    ";
   return ( s.substring(0,n));

// Simple function to grab the session stats and put them into JSON
function stats2json(sid){
     var binds = {};
     binds.SID = sid;

     var list = util2.executeReturnList("select name,value from v$statname sn,v$sesstat  s where sn.statistic# = s.STATISTIC# and s.SID= :SID",binds);
     var ret={};
     for (var i = 0; i < list.length; i++) {
             ret[list[i].NAME] = parseInt(list[i].VALUE);
   return ret;

// Simple function to grab the session details and put them into JSON
function getSession(util){
      /* Current active SQL Connection */
      var results = util.executeReturnList("select sys_context('USERENV','session_user') u,sys_context('USERENV','SESSIONID') sessionID,sys_context('USERENV','SID') sid from dual",null);

      var ret = {};
          ret.user      = results[0].U;
          ret.sid       = results[0].SID;
          ret.sessionid = results[0].SESSIONID;

      ctx.write("\tUser:" + ret.user + "\n");
      ctx.write("\tSID:" + ret.sid + "\n");
      ctx.write("\tSession:" + ret.sessionid + "\n");

     return ret;

// rebuild the arguments which are the commands to run
var sql="";
for(var i=1;i<args.length;i++){
  sql = sql + " " + args[i];

// print the sessions to prove they are different
ctx.write("--Work Session--\n");
var session = getSession(util);

ctx.write("--Monitor Session--\n");
var session2 = getSession(util2);

// grabt the stats before
var before = stats2json(session.sid);

// rebuild the sql from the arguments
ctx.write("Command:\n\t"+ sql + "\n\n");

// run it;

// get the after session stats
var after = stats2json(session.sid);

ctx.write("Session Stat Changes:\n\n");

// walk the stats and print the deltas
for(var key in before){
   // print only stats that changed
   if ( before[key] !=  after[key] ) {
     ctx.write( pad(key,64) + "\t\t "+ pad(before[key],12) + " --- "+ pad(after[key],12) + "\t "  );
     ctx.write( pad((after[key]-before[key]),12) + "\n");

Disqus for Kris' Blog