Leve.Iteration @TearDown method called one too many times

[Alex Averbuch]

Hi,
I have a benchmark for measuring database index creation.

Summary:
  * It is an expensive operation (5+ seconds per invocation), so
Mode.SingleShotTime is used
  * The database runs 5 warmup iterations & 5 measurement iterations
  * Each iteration must create an index from scratch, so the index must be
dropped/deleted between iterations
  * To delete the index after each iteration a Level.Iteration @TearDown
method is used. Inside this method the index is dropped

Problem:
  * It appears as though the Level.Iteration @TearDown method is being
called 1 more time than the @Benchmark method
  * This causes the database (and benchmark) to crash, because the database
tries to delete an index that does not exist

When executing the benchmark code at the bottom of this email, the
following is written to console:

# Run progress: 0.00% complete, ETA 00:00:00
# Fork: 1 of 1
# Warmup Iteration   1:
CREATE
DROP
# Warmup Iteration   2:
CREATE
DROP
# Warmup Iteration   3:
CREATE
DROP
# Warmup Iteration   4:
CREATE
DROP
# Warmup Iteration   5:
CREATE
DROP
Iteration   1:
CREATE
DROP
Iteration   2:
CREATE
DROP
Iteration   3:
CREATE
DROP
Iteration   4:
CREATE
DROP
Iteration   5:
CREATE
DROP
DROP                                   <--------- NOTICE THIS ADDITIONAL
"DROP"



Does this (extra DROP) make sense?
Is there any way to prevent it from happening?
Thanks in advance!


@State( Scope.Benchmark )
public class CreateIndex
{
    protected Database db;

    @Setup
    public void setUp()
    {
        db = new Database();
        // populate db
    }

    @TearDown
    public void tearDown()
    {
        db.shutdown();
    }

    @TearDown( Level.Iteration )
    public void dropIndex()
    {
        System.out.println("DROP");
        try ( Transaction tx = db.beginTx() )
        {
            // drop index
            tx.success();
        }
    }

    @Benchmark
    @BenchmarkMode( Mode.SingleShotTime )
    public void createIndex()
    {
        System.out.println("CREATE");
        try ( Transaction tx = db.beginTx() )
        {
            // create index
            tx.success();
        }
    }
}