MDEV-9637 select nullif(count(col1),0) gives wrong result if in a view

don't do special SUM_FUNC_ITEM treatment in NULLIF for views
(as before), but do it for derived tables (when
context_analysis_only == CONTEXT_ANALYSIS_ONLY_DERIVED)

mysql-test/r/null.result

@@ -1531,6 +1531,17 @@ View	Create View	character_set_client	collation_connection
 v1	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `v1` AS select nullif(count(distinct `t1`.`col1`),0) AS `nullif(count(distinct col1),0)` from `t1`	latin1	latin1_swedish_ci
 drop view v1;
 drop table t1;
+create table t1 (col1 varchar(50) default null);
+insert into t1 (col1) values ('hello'), ('hello'), ('hello');
+create view v1 as select nullif(count(col1),0) from t1;
+select * from v1;
+nullif(count(col1),0)
+3
+select nullif(count(col1),0) from t1;
+nullif(count(col1),0)
+3
+drop view v1;
+drop table t1;
 #
 # End of 10.1 tests
 #

mysql-test/t/null.test

@@ -958,6 +958,17 @@ show create view v1;
 drop view v1;
 drop table t1;
 
+#
+# MDEV-9637 select nullif(count(col1),0) gives wrong result if in a view
+#
+create table t1 (col1 varchar(50) default null);
+insert into t1 (col1) values ('hello'), ('hello'), ('hello');
+create view v1 as select nullif(count(col1),0) from t1;
+select * from v1;
+select nullif(count(col1),0) from t1;
+drop view v1;
+drop table t1;
+
 --echo #
 --echo # End of 10.1 tests
 --echo #

sql/item_cmpfunc.cc

@@ -2584,7 +2584,8 @@ Item_func_nullif::fix_length_and_dec()
     args[0] and args[2] should still point to the same original l_expr.
   */
   DBUG_ASSERT(args[0] == args[2] || thd->stmt_arena->is_stmt_execute());
-  if (args[0]->type() == SUM_FUNC_ITEM && !thd->lex->context_analysis_only)
+  if (args[0]->type() == SUM_FUNC_ITEM &&
+      !thd->lex->is_ps_or_view_context_analysis())
   {
     /*
       NULLIF(l_expr, r_expr)