You may have noticed the FILES "scripts" - they look quite innocent:
but concerning speed, they can be devastating:
dt1 = new table("test",<< add rows(1), new column ("x", set each value(1)));
t0=hptime();
Nmax=200;
for(i=1, i<100,i++,
filesN = As list(Index(1,Nmax)`);
filelist = transform each({i},filesN,Eval List({"myfile"||Char(i)||".txt", 1, 1}));
Eval (Eval Expr(
dt1 << New Table Script( "Files",Expr(filelist) )
)));
time=(hptime()-t0)/1000000;
print("add files info: ", time);
dt2 = dt1 << Subset( All rows, Selected columns only( 0 ) );
t0= hptime();
dt1 << Concatenate( dt2);
time=(hptime()-t0)/1000000;
print("concat 2 files: ", time);