message: reproducing the issue
diff: # DuckDB needs to have been built with TPCH (BUILD_TPCH=1) to run this test!
  @testset "Test TPC-H Multithreaded" begin
  - sf = "0.01"
  + sf = "0.1"
  # load TPC-H into DuckDB
  native_con = DBInterface.connect(DuckDB.DB)
  + #df_con = DBInterface.connect(DuckDB.DB)
  DBInterface.execute(native_con, "CALL dbgen(sf=$sf)")
  # convert all tables to Julia DataFrames
  supplier = DataFrame(DBInterface.execute(native_con, "SELECT * FROM supplier"))
  Threads.@threads for _ in 1:Threads.nthreads()
  - db = DuckDB.DB()
  + #db = DuckDB.DB()
  id = Threads.threadid()
  # now open a new in-memory database, and register the dataframes there
  - df_con = DBInterface.connect(db)
  + df_con = DBInterface.connect(DuckDB.DB)
  #DBInterface.execute(df_con, "SET external_threads=1");
  DuckDB.register_data_frame(df_con, customer, "customer")
  DuckDB.register_data_frame(df_con, lineitem, "lineitem")
  #throw(UndefVarError(:df_con))
  # Execute all the queries
  - for i in 1:100
  + for _ in 1:100
  + for i in 1:22
  print("T:$id | Q:$i\n")
  - res = DataFrame(DBInterface.execute(df_con, "PRAGMA tpch(1)"))
  + res = DataFrame(DBInterface.execute(df_con, "PRAGMA tpch($i)"))
  + end
  end
  DBInterface.close!(df_con)
  end
  