LOAD 'pg_hint_plan';
-SET pg_hint_plan.enable TO on;
+SET pg_hint_plan.enable_hint TO on;
SET pg_hint_plan.debug_print TO on;
SET client_min_messages TO LOG;
SET search_path TO public;
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r1
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Nested Loop
Join Filter: (b1t1.c1 = b1t3.c1)
-> Nested Loop
- Join Filter: (b1t2.c1 = b1t1.c1)
+ Join Filter: (b1t1.c1 = b1t2.c1)
-> Nested Loop
-> Tid Scan on r1_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b1t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b1t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b1t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b1t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b1t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b1t4
-> Hash Join
Hash Cond: (b1t1.c1 = b1t4.c1)
-> Hash Join
- Hash Cond: (b1t2.c1 = b1t1.c1)
+ Hash Cond: (b1t1.c1 = b1t2.c1)
-> Hash Join
- Hash Cond: (b1t3.c1 = b1t2.c1)
+ Hash Cond: (b1t3.c1 = b1t1.c1)
-> Seq Scan on t3 b1t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b1t2
+ -> Seq Scan on t1 b1t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b1t1
+ -> Seq Scan on t2 b1t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b1t4
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r2
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r2
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Nested Loop
Join Filter: (b1t1.c1 = b1t3.c1)
-> Nested Loop
- Join Filter: (b1t2.c1 = b1t1.c1)
+ Join Filter: (b1t1.c1 = b1t2.c1)
-> Nested Loop
-> Tid Scan on r2_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b1t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b1t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b1t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b1t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b1t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b1t4
-> Nested Loop
Join Filter: (b2t1.c1 = b2t3.c1)
-> Nested Loop
- Join Filter: (b2t2.c1 = b2t1.c1)
+ Join Filter: (b2t1.c1 = b2t2.c1)
-> Nested Loop
-> Tid Scan on r2_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b2t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b2t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b2t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b2t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b2t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b2t4
-> Hash Join
Hash Cond: (b1t1.c1 = b1t4.c1)
-> Hash Join
- Hash Cond: (b1t2.c1 = b1t1.c1)
+ Hash Cond: (b1t1.c1 = b1t2.c1)
-> Hash Join
- Hash Cond: (b1t3.c1 = b1t2.c1)
+ Hash Cond: (b1t3.c1 = b1t1.c1)
-> Seq Scan on t3 b1t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b1t2
+ -> Seq Scan on t1 b1t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b1t1
+ -> Seq Scan on t2 b1t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b1t4
-> Hash Join
Hash Cond: (b2t1.c1 = b2t4.c1)
-> Hash Join
- Hash Cond: (b2t2.c1 = b2t1.c1)
+ Hash Cond: (b2t1.c1 = b2t2.c1)
-> Hash Join
- Hash Cond: (b2t3.c1 = b2t2.c1)
+ Hash Cond: (b2t3.c1 = b2t1.c1)
-> Seq Scan on t3 b2t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b2t2
+ -> Seq Scan on t1 b2t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b2t1
+ -> Seq Scan on t2 b2t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b2t4
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r3
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r3
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Nested Loop
Join Filter: (t1.c1 = t3.c1)
-> Nested Loop
- Join Filter: (t2.c1 = t1.c1)
+ Join Filter: (t1.c1 = t2.c1)
-> Nested Loop
-> Tid Scan on r3
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Hash Join
Hash Cond: (t1.c1 = t4.c1)
-> Hash Join
- Hash Cond: (t2.c1 = t1.c1)
+ Hash Cond: (t1.c1 = t2.c1)
-> Hash Join
- Hash Cond: (t3.c1 = t2.c1)
+ Hash Cond: (t3.c1 = t1.c1)
-> Seq Scan on t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2
+ -> Seq Scan on t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1
+ -> Seq Scan on t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4
-> Nested Loop
Join Filter: (b1t1.c1 = b1t3.c1)
-> Nested Loop
- Join Filter: (b1t2.c1 = b1t1.c1)
+ Join Filter: (b1t1.c1 = b1t2.c1)
-> Nested Loop
-> Tid Scan on r3_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b1t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b1t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b1t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b1t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b1t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b1t4
-> Nested Loop
Join Filter: (b2t1.c1 = b2t3.c1)
-> Nested Loop
- Join Filter: (b2t2.c1 = b2t1.c1)
+ Join Filter: (b2t1.c1 = b2t2.c1)
-> Nested Loop
-> Tid Scan on r3_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b2t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b2t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b2t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b2t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b2t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b2t4
-> Nested Loop
Join Filter: (b3t1.c1 = b3t3.c1)
-> Nested Loop
- Join Filter: (b3t2.c1 = b3t1.c1)
+ Join Filter: (b3t1.c1 = b3t2.c1)
-> Nested Loop
-> Tid Scan on r3_
TID Cond: (ctid = '(1,1)'::tid)
Filter: (c1 = 1)
- -> Seq Scan on t2 b3t2
- Filter: (ctid = '(1,1)'::tid)
- -> Tid Scan on t1 b3t1
- TID Cond: (ctid = '(1,1)'::tid)
+ -> Tid Scan on t1 b3t1
+ TID Cond: (ctid = '(1,1)'::tid)
+ -> Seq Scan on t2 b3t2
+ Filter: (ctid = '(1,1)'::tid)
-> Tid Scan on t3 b3t3
TID Cond: (ctid = '(1,1)'::tid)
-> Tid Scan on t4 b3t4
-> Hash Join
Hash Cond: (b1t1.c1 = b1t4.c1)
-> Hash Join
- Hash Cond: (b1t2.c1 = b1t1.c1)
+ Hash Cond: (b1t1.c1 = b1t2.c1)
-> Hash Join
- Hash Cond: (b1t3.c1 = b1t2.c1)
+ Hash Cond: (b1t3.c1 = b1t1.c1)
-> Seq Scan on t3 b1t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b1t2
+ -> Seq Scan on t1 b1t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b1t1
+ -> Seq Scan on t2 b1t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b1t4
-> Hash Join
Hash Cond: (b2t1.c1 = b2t4.c1)
-> Hash Join
- Hash Cond: (b2t2.c1 = b2t1.c1)
+ Hash Cond: (b2t1.c1 = b2t2.c1)
-> Hash Join
- Hash Cond: (b2t3.c1 = b2t2.c1)
+ Hash Cond: (b2t3.c1 = b2t1.c1)
-> Seq Scan on t3 b2t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b2t2
+ -> Seq Scan on t1 b2t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b2t1
+ -> Seq Scan on t2 b2t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b2t4
-> Hash Join
Hash Cond: (b3t1.c1 = b3t4.c1)
-> Hash Join
- Hash Cond: (b3t2.c1 = b3t1.c1)
+ Hash Cond: (b3t1.c1 = b3t2.c1)
-> Hash Join
- Hash Cond: (b3t3.c1 = b3t2.c1)
+ Hash Cond: (b3t3.c1 = b3t1.c1)
-> Seq Scan on t3 b3t3
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t2 b3t2
+ -> Seq Scan on t1 b3t1
Filter: (ctid = '(1,1)'::tid)
-> Hash
- -> Seq Scan on t1 b3t1
+ -> Seq Scan on t2 b3t2
Filter: (ctid = '(1,1)'::tid)
-> Hash
-> Seq Scan on t4 b3t4
RESET client_min_messages;
----
+---- No. G-2-1 GUC parameter
+----
+-- No. G-2-1-3
+/*+Set(1234567890123456789012345678901234567890123456789012345678901234 1)*/
+SELECT * FROM s1.t1 WHERE t1.c1 = 1;
+NOTICE: identifier "1234567890123456789012345678901234567890123456789012345678901234" will be truncated to "123456789012345678901234567890123456789012345678901234567890123"
+INFO: unrecognized configuration parameter "123456789012345678901234567890123456789012345678901234567890123"
+ c1 | c2 | c3 | c4
+----+----+----+----
+ 1 | 1 | 1 | 1
+(1 row)
+
+-- No. G-2-1-4
+/*+Set(constraint_exclusion 1234567890123456789012345678901234567890123456789012345678901234)*/
+SELECT * FROM s1.t1 WHERE t1.c1 = 1;
+INFO: invalid value for parameter "constraint_exclusion": "1234567890123456789012345678901234567890123456789012345678901234"
+HINT: Available values: partition, on, off.
+ c1 | c2 | c3 | c4
+----+----+----+----
+ 1 | 1 | 1 | 1
+(1 row)
+
+----
---- No. G-2-2 category of GUC parameter and role
----
-- No. G-2-2-1
-- No. G-2-3-1
/*+Set(enable_indexscan on)Set(enable_indexscan off)*/
SELECT * FROM s1.t1 WHERE false;
-INFO: hint syntax error at or near "Set(enable_indexscan on)Set(enable_indexscan off)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(enable_indexscan on)Set(enable_indexscan off)"
DETAIL: Conflict set hint.
LOG: pg_hint_plan:
used hint:
-- No. G-2-3-2
/*+Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBUG2)*/
SELECT * FROM s1.t1 WHERE false;
-INFO: hint syntax error at or near "Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBUG2)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBUG2)"
DETAIL: Conflict set hint.
-INFO: hint syntax error at or near "Set(client_min_messages WARNING)Set(client_min_messages DEBUG2)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(client_min_messages WARNING)Set(client_min_messages DEBUG2)"
DETAIL: Conflict set hint.
LOG: pg_hint_plan:
used hint:
-- No. G-2-3-3
/*+Set(enable_indexscan on)Set(enable_indexscan o)*/
SELECT * FROM s1.t1 WHERE false;
-INFO: hint syntax error at or near "Set(enable_indexscan on)Set(enable_indexscan o)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(enable_indexscan on)Set(enable_indexscan o)"
DETAIL: Conflict set hint.
INFO: parameter "enable_indexscan" requires a Boolean value
LOG: pg_hint_plan:
-- No. G-2-3-4
/*+Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBU)*/
SELECT * FROM s1.t1 WHERE false;
-INFO: hint syntax error at or near "Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBU)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(client_min_messages DEBUG5)Set(client_min_messages WARNING)Set(client_min_messages DEBU)"
DETAIL: Conflict set hint.
-INFO: hint syntax error at or near "Set(client_min_messages WARNING)Set(client_min_messages DEBU)"
+INFO: pg_hint_plan: hint syntax error at or near "Set(client_min_messages WARNING)Set(client_min_messages DEBU)"
DETAIL: Conflict set hint.
INFO: invalid value for parameter "client_min_messages": "DEBU"
HINT: Available values: debug5, debug4, debug3, debug2, debug1, log, notice, warning, error.
-- No. G-2-4-1
/*+SeqScan(a)IndexScan(a)SeqScan(c)NestLoop(a) */
SELECT * FROM s1.t1 a, s1.t2 b WHERE false;
-INFO: hint syntax error at or near ") "
+INFO: pg_hint_plan: hint syntax error at or near " "
DETAIL: NestLoop hint requires at least two relations.
-INFO: hint syntax error at or near "SeqScan(a)IndexScan(a)SeqScan(c)NestLoop(a) "
+INFO: pg_hint_plan: hint syntax error at or near "SeqScan(a)IndexScan(a)SeqScan(c)NestLoop(a) "
DETAIL: Conflict scan method hint.
LOG: pg_hint_plan:
used hint: