i read documents,i find it that concurrent index create don't lock write.but need scan table twice.it explain is following as: It scans the table once to initially build the index, then makes a second pass to look for things added after the first pass.
please explain 1. what happens when concurrent index create .tks. 2.how to trace a backend what do somethings internal.for example oracle 10046 trace.
It seems you are looking for a similar behavior of sql_trace in oracle. You can try pgstatstatements contrib module.