Github user comnetwork commented on a diff in the pull request:
https://github.com/apache/phoenix/pull/314#discussion_r206012706
--- Diff:
phoenix-core/src/main/java/org/apache/phoenix/expression/Expression.java ---
@@ -88,4 +88,10 @@
* @return
*/
boolean requiresFinalEvaluation();
+
+ /**
+ *
+ * @return
+ */
+ boolean isConstantIfChildrenAllConstant();
--- End diff --
I think ExpressionUtil.isConstant(Expression) is not suitable for this
case, just as the comments of jira said, what we want to check in this issue is
if a expression is constant when all children of it are constants, just
consider following sql:
select a.ak3 from
(select rand() ak1,length(pk2) ak2,length(pk3) ak3,length(v1)
av1,length(v2) av2 from test order by pk2,pk3 limit 10) a
where a.ak1 = 0.0 and a.av2 = length(substr('abc',1,1))
group by a.ak3,CASE WHEN coalesce(a.ak1,1) > coalesce(a.av2,2) THEN
coalesce(a.ak1,1) ELSE coalesce(a.av2,2) END,a.av1
order by a.ak3,a.av1
Obviously , because of rand(), the Determinism of expression a.ak1 is
Determinism.PER_INVOCATION, so the determinism is Determinism.PER_INVOCATION
and isStateless is false for expression "CASE WHEN coalesce(a.ak1,1) >
coalesce(a.av2,2) THEN coalesce(a.ak1,1) ELSE coalesce(a.av2,2) END", but
because the a.ak1 and a.av2 are both constants in where clause of outer query,
we can regard "CASE WHEN coalesce(a.ak1,1) > coalesce(a.av2,2) THEN
coalesce(a.ak1,1) ELSE coalesce(a.av2,2) END" as constant in IsConstantVisitor.
---
