Build out the planner support function infrastructure.

Add support function requests for estimating the selectivity, cost,
and number of result rows (if a SRF) of the target function.

The lack of a way to estimate selectivity of a boolean-returning
function in WHERE has been a recognized deficiency of the planner
since Berkeley days.  This commit finally fixes it.

In addition, non-constant estimates of cost and number of output
rows are now possible.  We still fall back to looking at procost
and prorows if the support function doesn't service the request,
of course.

To make concrete use of the possibility of estimating output rowcount
for SRFs, this commit adds support functions for array_unnest(anyarray)
and the integer variants of generate_series; the lack of plausible
rowcount estimates for those, even when it's obvious to a human,
has been a repeated subject of complaints.  Obviously, much more
could now be done in this line, but I'm mostly just trying to get
the infrastructure in place.

Discussion: https://postgr.es/m/[email protected]

1 files changed, 1 insertions, 2 deletions

diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index ceec85db925..16b0b1d2dcc 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -120,8 +120,7 @@ extern char func_volatile(Oid funcid);
 extern char func_parallel(Oid funcid);
 extern char get_func_prokind(Oid funcid);
 extern bool get_func_leakproof(Oid funcid);
-extern float4 get_func_cost(Oid funcid);
-extern float4 get_func_rows(Oid funcid);
+extern RegProcedure get_func_support(Oid funcid);
 extern Oid	get_relname_relid(const char *relname, Oid relnamespace);
 extern char *get_rel_name(Oid relid);
 extern Oid	get_rel_namespace(Oid relid);