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Notes and Further References

The DatabaseInterface is fully described in the User Manual

In order to read any Database table supported by the DatabaseInterface../../../UgliGeometry package, you need to have a context. This concept was introduced in the Validity slide and the associated notes explained how to get a VldContext for a RawRecord:-

  const VldContext* vc = raw->GetVldContext();

Once there you can create a pointer to any supported database table. For example UgliGeometry has the table UgliDbiSteelPln, so at minimum, all you need to do to get the table of UgliDbiSteelPln rows that are currently valid is:- DbiResultPtr<UgliDbiSteelPln> rptr(vc); Note that DbiResultPtr is a templated class. The compiler takes the real class UgliDbiSteelPln and generates the associated DbiResultPtr class. We will come back to the UgliDbiSteelPln when we get to UgliGeometry, however if you take a quick peek at UgliDbiSteelPln.h which includes:- Float_t GetZBack() const; you will have a message to send an UgliDbiSteelPln once DbiResultPtr has given you one from the table:- UInt_t numRows = rptr.GetNumRows(); const UgliDbiSteelPln* firstPln = rptr.GetRow(0); const UgliDbiSteelPln* lastPln = rptr.GetRow(numRows-1); cout << "There are " << numRows << " steel planes" << " Z limits: " << firstPln->GetZBack() << " .. " << lastPln->GetZBack() << endl; Pulling data from that database can be expensive so the DatabaseInterface caches data in case its reused. time_dbi.C is a complete ROOT macro to demonstrate this.

time_dbi()

The controlling main program is very similar to ones we have seen before. See the Writing_ROOT_macros if you need help.

void myAnaTimeDbi(const MomNavigator* mom)

Has the code that does the timing.

void myAnaTimeDbi(const MomNavigator* mom) 
{
  RawRecord* raw = dynamic_cast<RawRecord*>(mom->GetFragment("RawRecord"));
  const VldContext* vc = raw->GetVldContext();   

  TStopwatch t;   
  t.Start();
  DbiResultPtr<PlexPixelSpotToStripEnd> rptr(*vc);
  t.Stop();
  UInt_t numRows = rptr.GetNumRows();
  cout << "There are " << numRows << " rows" 
       << " cpu " << t.CpuTime()  << " elapse " << t.RealTime() << endl;
}

TStopwatch is a little ROOT class that you can send Start() and Stop() messages to and ask it for CpuTime() and RealTime().

Its used to time the creation of a DbiResultPtr to a PlexPixelSpotToStripEnd table:-

DbiResultPtr<PlexPixelSpotToStripEnd> rptr(*vc); As you have probably noticed, this time we are reading a Plex table.

When I run:-

  loon -q time_dbi.C $ROOT_DATA/fardet_data/2002_06/F00005963_0000.mdaq.root

I get:- Successfully opened connection to: mysql:odbc://localhost/offline DbiCascader Status:- Status URL Open mysql:odbc://localhost/offline DbiTimer:PLEXPIXELSPOTTOSTRIPEND: Query done. 190464rows, 6.1Mb Cpu 143.4 , elapse 154.8 SubWatch Query database : Cpu 1.8 , elapse 10.8 , Starts 2 SubWatch Create row objects : Cpu 24.0 , elapse 24.4 , Starts 190466 SubWatch Retrieve TSQL rows : Cpu 8.2 , elapse 8.2 , Starts 190465 SubWatch Fill row objects : Cpu 108.9 , elapse 110.8 , Starts 190465 There are 190464 rows cpu 144.090000 elapse 158.880000 There are 190464 rows cpu 0.000000 elapse 0.000000 There are 190464 rows cpu 0.000000 elapse 0.000000 There are 190464 rows cpu -0.000000 elapse 0.000000 There are 190464 rows cpu 0.000000 elapse 0.000000 There are 190464 rows cpu 0.000000 elapse -0.000000 There are 190464 rows cpu -0.000000 elapse 0.000000 There are 190464 rows cpu 0.000000 elapse 0.000000 There are 190464 rows cpu -0.000000 elapse 0.000000 There are 190464 rows cpu 0.010000 elapse 0.010000 The important point to note is that there is significant cpu and elapse time for the first call, but after that, and even though the local DbiResultPtr has been destroyed and recreated, the times are below the resolution of the timer because the data is coming from the cache.

Exercises

Here is a list of some of the Plex and UgilGeometry table row classes we have:-

By adapting the above macro try to create DbiResultPtrs to look at some of the tables and access the individual table row objects.

Contact: Nick West <n.west1@physics.ox.ac.uk>


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