planner: Fix predicate simplification panic caused by zero-argument e…

…xpressions like rand() (pingcap#56947)

close pingcap#56270

pkg/planner/core/rule_predicate_simplification.go

@@ -55,6 +55,9 @@ func findPredicateType(expr expression.Expression) (*expression.Column, predicat
 			return nil, orPredicate
 		}
 		args := v.GetArgs()
+		if len(args) == 0 {
+			return nil, otherPredicate
+		}
 		col, colOk := args[0].(*expression.Column)
 		if !colOk {
 			return nil, otherPredicate

tests/integrationtest/r/planner/core/issuetest/planner_issue.result

@@ -750,3 +750,9 @@ NULL	NULL	2	2	4	2
 show warnings;
 Level	Code	Message
 drop table if exists t1, t2, t3, t4;
+drop table if exists t0, v0;
+drop view if exists v0;
+CREATE  TABLE  t0(c0 INTEGER);
+CREATE VIEW v0(c0) AS SELECT 'a' FROM t0 WHERE (CASE t0.c0 WHEN t0.c0 THEN false END );
+SELECT t0.c0 FROM v0, t0 WHERE RAND();
+c0

tests/integrationtest/t/planner/core/issuetest/planner_issue.test

@@ -517,3 +517,10 @@ SELECT t2.a,t2.b,t3.a,t3.b,t4.a,t4.b
        ON t3.a=1 AND t3.b=t2.b AND t2.b=t4.b order by 1, 2, 3, 4, 5;
 show warnings;
 drop table if exists t1, t2, t3, t4;
+
+# TestIssue56270
+drop table if exists t0, v0;
+drop view if exists v0;
+CREATE  TABLE  t0(c0 INTEGER);
+CREATE VIEW v0(c0) AS SELECT 'a' FROM t0 WHERE (CASE t0.c0 WHEN t0.c0 THEN false END );
+SELECT t0.c0 FROM v0, t0 WHERE RAND();