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. -- View this message in context: http://postgresql.1045698.n5.nabble.com/what-happens-when-concurrent-index-create-tp5615720p5615720.html Sent from the PostgreSQL - general mailing list archive at Nabble.com. -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general