Jeff Amiel <becauseimjeff@xxxxxxxxx> writes: > What is the difference between: > select foo(); > and > select * from foo(); They're implemented differently, partly for legacy or lack-of-round-tuit reasons, and partly because different PLs prefer different strategies for returning sets. The first form only works for functions that are able to return one row at a time, ie, suspend execution of a SRF until called again. I think currently that is only true of SQL-language and some C functions. The outer SELECT just returns the rows one at a time as they're returned by the function. In the second form the function is immediately executed to completion and all the result rows are stuffed in a tuplestore. The surrounding query then runs and draws the rows from the tuplestore. This is particularly convenient for PLs like plpgsql, which return set results as tuplestores in the first place, but we'll create a tuplestore anyway if the function wants to return the rows one at a time. regards, tom lane
