Fixed sporadically failing test show_explain_json.test

Code taken from MDEV-33423: show_analyze sporadically fails

Thanks to Sergei Petrunia for pointing this out.

mysql-test/main/show_explain_json.result

@@ -518,9 +518,12 @@ SET debug_dbug=@old_debug;
 # Try to do SHOW EXPLAIN for a query that runs a  SET command:
 #   I've found experimentally that select_id==2 here...
 #
-set @show_explain_probe_select_id=2;
+create table t2 (a int);
+insert into t2 values (1),(2);
+set @show_explain_probe_select_id=3;
 SET debug_dbug='+d,show_explain_probe_join_exec_start';
-set @foo= (select max(a) from t0 where sin(a) >0);
+set @foo= (select max(a) from t2
+where a + (select max(a) from t0 where t0.a>t2.a) < 10000);
 connection default;
 show explain format=JSON for $thr2;
 ERROR HY000: Target is not executing an operation with a query plan
@@ -528,6 +531,7 @@ kill query $thr2;
 connection con1;
 ERROR 70100: Query execution was interrupted
 SET debug_dbug=@old_debug;
+drop table t2;
 #
 # Attempt SHOW EXPLAIN for an UPDATE
 #

mysql-test/main/show_explain_json.test

@@ -271,9 +271,16 @@ SET debug_dbug=@old_debug;
 --echo # Try to do SHOW EXPLAIN for a query that runs a  SET command:
 --echo #   I've found experimentally that select_id==2 here...
 --echo #
-set @show_explain_probe_select_id=2;
+
+create table t2 (a int);
+insert into t2 values (1),(2);
+set @show_explain_probe_select_id=3; # Stop in the subquery.
 SET debug_dbug='+d,show_explain_probe_join_exec_start';
-send set @foo= (select max(a) from t0 where sin(a) >0);
+# t2 has 2 rows so we will stop in the subquery twice: 
+#  - first one to serve the SHOW ANALYZE request
+#  - second one when waiting to be KILLed.
+send set @foo= (select max(a) from t2
+                 where a + (select max(a) from t0 where t0.a>t2.a) < 10000);
 connection default;
 --source include/wait_condition.inc
 --error ER_TARGET_NOT_EXPLAINABLE
@@ -283,6 +290,7 @@ connection con1;
 --error ER_QUERY_INTERRUPTED
 reap;
 SET debug_dbug=@old_debug;
+drop table t2;
 
 --echo #
 --echo # Attempt SHOW EXPLAIN for an UPDATE