Laurenz Albe <laurenz.a...@cybertec.at> writes: > The SQL standard has the expression "NEXT VALUE FOR asequence" to do > what we traditionally do with "nextval('asequence')". > This is an attempt to implement this on top of the recently introduced > NextValueExpr node.
This has been proposed repeatedly, and rejected repeatedly, because in fact the standard's semantics for NEXT VALUE FOR are *not* like nextval(). See SQL:2011 4.22.2 "Operations involving sequence generators": If there are multiple instances of <next value expression>s specifying the same sequence generator within a single SQL-statement, all those instances return the same value for a given row processed by that SQL-statement. This is not terribly exact --- what is a "processed row" in a join query, for instance? But it's certainly not supposed to act like independent executions of nextval() or NextValueExpr would. Pending somebody doing the legwork to produce something that at least arguably conforms to the spec's semantics, we've left the syntax unimplemented. regards, tom lane