Re: [HACKERS] ExecMakeTableFunctionResult vs. pre-evaluated functions

[Joe Conway]

Tom Lane wrote:

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?

If presented with a non-function-call expression tree, can we always evaluate it to produce a scalar constant (if it isn't already)? If so, why not do that, create a one row, one column tuplestore, and exit? It's really no different than a function call that does the same, is it?

Joe



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