cliff@xxxxxxxxxxxxx writes: > suppose a table has a UNIQUE constraint on a column, and two > concurrent transactions attempt to INSERT a row with the same value > for that column: Whichever one manages to get to the index page first will go through. The second one will block waiting to see if the first one commits, and will error out if so --- or proceed, if it aborts. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your message can get through to the mailing list cleanly