+SET plantuner.enable_index="i_idx";
+SHOW plantuner.enable_index;
+ plantuner.enable_index
+------------------------
+ public.i_idx
+(1 row)
+
+SELECT * FROM wow;
+ i | j
+---+---
+(0 rows)
+
+--test only index
+RESET plantuner.disable_index;
+RESET plantuner.enable_index;
+SET enable_seqscan=off;
+SET enable_bitmapscan=off;
+SET enable_indexonlyscan=off;
+SET plantuner.only_index="i1";
+SHOW plantuner.only_index;
+ plantuner.only_index
+----------------------
+ public.i1
+(1 row)
+
+EXPLAIN (COSTS OFF) SELECT * FROM wow WHERE i = 0;
+ QUERY PLAN
+----------------------------
+ Index Scan using i1 on wow
+ Index Cond: (i = 0)
+(2 rows)
+
+SET plantuner.disable_index="i1,i2,i3";
+EXPLAIN (COSTS OFF) SELECT * FROM wow WHERE i = 0;
+ QUERY PLAN
+----------------------------
+ Index Scan using i1 on wow
+ Index Cond: (i = 0)
+(2 rows)
+
+SET plantuner.only_index="i2";
+EXPLAIN (COSTS OFF) SELECT * FROM wow WHERE i = 0;
+ QUERY PLAN
+----------------------------
+ Index Scan using i2 on wow
+ Index Cond: (i = 0)
+(2 rows)
+
+RESET plantuner.only_index;
+EXPLAIN (COSTS OFF) SELECT * FROM wow WHERE i = 0;
+ QUERY PLAN
+-------------------------------
+ Index Scan using i_idx on wow
+ Index Cond: (i = 0)
+(2 rows)
+