I've spent today messing with making the planner substitute inline definitions of simple SQL functions, per the comment in src/backend/optimizer/util/clauses.c:
* XXX Possible future improvement: if the func is SQL-language, and its * definition is simply "SELECT expression", we could parse and substitute * the expression here. This would avoid much runtime overhead, and perhaps * expose opportunities for constant-folding within the expression even if * not all the func's input args are constants. It'd be appropriate to do * that here, not in the parser, since we wouldn't want it to happen until * after rule substitution/rewriting. It seems to work 99%, but I'm seeing this failure in the regression tests: CREATE FUNCTION getfoo(int) RETURNS int AS 'SELECT $1;' LANGUAGE SQL; SELECT * FROM getfoo(1) AS t1; ! ERROR: ExecMakeTableFunctionResult: expression is not a function call which of course happens because the table-function expression has been reduced to just a constant "1" by the time the executor sees it. A grotty answer is to not apply constant-expression folding to table function RTE entries. A better answer would be to make ExecMakeTableFunctionResult more flexible, but I'm not quite sure what it should do if presented a non-function-call expression tree. Any thoughts? regards, tom lane PS: another little problem is regression=# explain SELECT * FROM getfoo(1) AS t1; server closed the connection unexpectedly but I'm sure that's just a lack of flexibility in explain.c ... ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster