if (pNumGroups)

{

*pNumGroups=subpath->rows;

*pNumGroups=estimate_num_groups(subroot,

get_tlist_exprs(subquery->targetList, false),

get_tlist_exprs(subroot->parse->targetList, false),

subpath->rows,

NULL,

NULL);

Filter: ((id IS NOT NULL) AND ((id * id) IS NOT NULL))

(3 rows)

-- Check the usage of a parse tree by the set operations (bug #18170)

explain (costs off)

SELECT c1.code FROM emp1 c1 LEFT JOIN emp1 c2 ON c1.id = c2.id

WHERE c2.id IS NOT NULL

EXCEPT ALL

SELECT c3.code FROM emp1 c3;

QUERY PLAN

----------------------------------------------

HashSetOp Except All

-> Append

-> Subquery Scan on "*SELECT* 1"

-> Seq Scan on emp1 c2

Filter: (id IS NOT NULL)

-> Subquery Scan on "*SELECT* 2"

-> Seq Scan on emp1 c3

(7 rows)

-- We can remove the join even if we find the join can't duplicate rows and

-- the base quals of each side are different. In the following case we end up

-- moving quals over to s1 to make it so it can't match any rows.

SELECTcount(*)FROM emp1 c1, emp1 c2, emp1 c3

WHEREc3.id=c2.idANDc3.id*c2.id=c1.id*c1.id;

explain (costs off)

SELECTc1.codeFROM emp1 c1LEFT JOIN emp1 c2ONc1.id=c2.id

WHEREc2.idIS NOT NULL

EXCEPT ALL

SELECTc3.codeFROM emp1 c3;