check_srf_call_placement() isn't always setting p_hasTargetSRFs

Hi,

while working on [1] (works, harmless regression check failures aside,
needs cleanup), I noticed $subject. Without fixing EXPR_KIND_VALUES to
set p_hasTargetSRFs the query has Query->hasTargetSRF wrongly set.
Which in turn breaks your planner code, as it's not being triggered
anymore.

Is there a reason not to just set p_hasTargetSRFs once towards the end
of the function, instead of doing so for all the non-error cases? That
fixes INSERT ... VALUES(generate_series()) with your approach for me.

I also noticed that we currently don't actually handle
Query->hasTargetSRF correct when said SRF is in a VALUES() block. As
there the SRFs are't in the targetlist

PlannerInfo *
subquery_planner(PlannerGlobal *glob, Query *parse,
PlannerInfo *parent_root,
bool hasRecursion, double tuple_fraction)
...
/* Constant-folding might have removed all set-returning functions */
if (parse->hasTargetSRFs)
parse->hasTargetSRFs = expression_returns_set((Node *) parse->targetList);

unsets that SRFs exist. I'm not really sure whether that's bad or good
- it right now doesn't cause active problems because of
transformInsertStmt's
/*
* Process INSERT ... VALUES with a single VALUES sublist. We treat
* this case separately for efficiency. The sublist is just computed
* directly as the Query's targetlist, with no VALUES RTE. So it
* works just like a SELECT without any FROM.
*/
optimization.

As we don't support SRFs in any other kind of values (ValuesNext calls
ExecEvalExpr isDone = NULL), that appears to be effectless right now.
But we'd get better errormessage if we made check_srf_call_placement()
error out. I wonder if there should be a seperate expression type for
the INSERT ... VALUES(exactly-one-row); since that behaves quite
differently.

Greetings,

Andres Freund

[1] http://archives.postgresql.org/message-id/20170116032952.z2re55hcfhzbkmrm%40alap3.anarazel.de