ProxySQL 2.0.6 fails to set session variable OPTIMIZER_SWITCH

[Trofym]

ProxySQL 2.0.6 fails to change switchable optimizations via session variable OPTIMIZER_SWITCH, but in ProxySQL 2.0.5 it works as expected.
Please return to old behaviour.
OS = CentOS 7.5

proxy > select version();
+-------------------+
| version()         |
+-------------------+
| 2.0.6-73-gc746bf7 |
+-------------------+


proxy > select @@OPTIMIZER_SWITCH\G
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

proxy > SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=off";
Query OK, 0 rows affected (0.00 sec)

proxy > select @@OPTIMIZER_SWITCH\G
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=off,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

proxy > SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=default";
Query OK, 0 rows affected (0.00 sec)

proxy > select @@OPTIMIZER_SWITCH\G
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,condition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

Record from error log:

2019-08-16 17:54:16 MySQL_Session.cpp:5094:handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY_qpo(): [WARNING] Unable to parse unknown SET query. Setting lock_hostgroup. Please report a bug for future enhancements:SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=off"
2019-08-16 17:54:32 MySQL_Session.cpp:5102:handler___status_WAITING_CLIENT_DATA___STATE_SLEEP___MYSQL_COM_QUERY_qpo(): [WARNING] Unable to parse unknown SET query. Not setting lock_hostgroup because already set. Please report a bug for future enhancements: SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=default"

Same test on ProxySQL 2.0.5:

proxy > select version();
+-------------------+
| version()         |
+-------------------+
| 2.0.5-37-gc8e32ee |
+-------------------+

proxy > select @@OPTIMIZER_SWITCH\G
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=o
n,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,con
dition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

proxy >  SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=off";                                                                                                                       
Query OK, 0 rows affected (0.00 sec)

proxy > select @@OPTIMIZER_SWITCH\G                                                                                                                                                           
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=off,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=
on,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,co
ndition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

proxy >  SET SESSION OPTIMIZER_SWITCH = "index_merge_intersection=default";                                                                                                                   
Query OK, 0 rows affected (0.00 sec)

proxy > select @@OPTIMIZER_SWITCH\G                                                                                                                                                           
*************************** 1. row ***************************
@@OPTIMIZER_SWITCH: index_merge=on,index_merge_union=on,index_merge_sort_union=on,index_merge_intersection=on,engine_condition_pushdown=on,index_condition_pushdown=on,mrr=on,mrr_cost_based=o
n,block_nested_loop=on,batched_key_access=off,materialization=on,semijoin=on,loosescan=on,firstmatch=on,duplicateweedout=on,subquery_materialization_cost_based=on,use_index_extensions=on,con
dition_fanout_filter=on,derived_merge=on
1 row in set (0.00 sec)

[renecannao]

@Trofym : it doesn't look like it fails, but it succeeds.
The error log is noisy, but it is saying it is disabling multiplexing because it doesn't recognize the SET command.
In this case, 2.0.6 behaves correctly, while 2.0.5 doesn't (it keeps multiplexing enabled)

[Trofym]

@renecannao I agree, 2.0.6 behaves correctly, but we use this kind of queries very frequently and error log became big and messy. Can you add such query to exeption and not display as warning in error log?