PostgreSQL :pg_stat_statements 和 pg_hint_plan

我在 PgDay Austria 上展示 pg_hint_plan 时遇到了这个问题（我将在postgresconf.org上再次在线展示）：当向查询中添加提示时， queryidin是否会改变？pg_stat_statements

简短的回答是：不，它不会改变，它queryid是根据解析后分析树计算的，忽略注释，这包括提示。

但这也回答了另一个问题：我们是否在查询文本中看到了注入的提示？这是一个小演示，表明即使从hint_plan.hints表中修改查询，queryid与查询文本相同也与没有提示相同。

我从我的演示中创建了表格：

create table a (n int primary key, x int);
create table b (n int primary key, x int);
create table c (n int primary key, x int);
create index b_index on b(x) include (n);
select pg_stat_statements_reset();
select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
select queryid, calls, rows, query from pg_stat_statements;

我检查queryid来自pg_stat_statements：

yugabyte=# select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
select queryid, calls, rows, query from pg_stat_statements;LOG:  statement: select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
 n | x
---+---
(0 rows)

yugabyte=# select queryid, calls, rows, query from pg_stat_statements;

       queryid       | calls | rows |                           query
---------------------+-------+------+-----------------------------------------------------------
 6990186059047281266 |     1 |    1 | select pg_stat_statements_reset()
 6386600050796028530 |     1 |    0 | select * from c "🍒" natural join b "🍌" natural join a "🍏"
(2 rows)

现在有了hint_plan表格中的提示：

grant yb_extension to yugabyte;
create extension pg_hint_plan;
set pg_hint_plan.enable_hint_table=on;
insert into hint_plan.hints(norm_query_string, application_name, hints) values (
$$select * from c "🍒" natural join b "🍌" natural join a "🍏" ;$$,
$$$$,
$hints$Leading( ( ("🍏" "🍌") "🍒" ) ) HashJoin( "🍏" "🍌" ) HashJoin("🍏" "🍌" "🍒") SeqScan("🍏") IndexOnlyScan("🍌") SeqScan("🍒")$hints$
);

我看到了同样的声明 and queryid：

yugabyte=# select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
select queryid, calls, rows, query from pg_stat_statements; n | x
---+---
(0 rows)

yugabyte=# select queryid, calls, rows, query from pg_stat_statements;
       queryid        | calls | rows |                                                                              query
----------------------+-------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------
 -4857947532354760446 |     3 |    1 | SELECT hints   FROM hint_plan.hints  WHERE norm_query_string = $1    AND ( application_name = $2     OR application_name = '' )  ORDER BY application_name DESC
  6990186059047281266 |     1 |    1 | select pg_stat_statements_reset()
  6386600050796028530 |     1 |    0 | select * from c "🍒" natural join b "🍌" natural join a "🍏"
(3 rows)

那么，我怎么知道这个提示被使用了呢？我可以启用详细日志：

yugabyte=# set pg_hint_plan.debug_print=verbose;
SET
yugabyte=# set client_min_messages = log;
SET
yugabyte=# select pg_stat_statements_reset();
LOG:  statement: select pg_stat_statements_reset();
LOG:  pg_hint_plan[qno=0x1a]: no match found in table:  application name = "psql", normalized_query="select pg_stat_statements_reset();"
LOG:  hints in comment="(none)", query="select pg_stat_statements_reset();", debug_query_string="select pg_stat_statements_reset();"
LOG:  pg_hint_plan[qno=0x1c]: no match found in table:  application name = "psql", normalized_query="select pg_stat_statements_reset();"
LOG:  hints in comment="(none)", query="select pg_stat_statements_reset();", debug_query_string="select pg_stat_statements_reset();"
LOG:  pg_hint_plan[qno=0x1a]: planner: no valid hint
 pg_stat_statements_reset
--------------------------

(1 row)

yugabyte=# select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
select queryid, calls, rows, query from pg_stat_statements;LOG:  statement: select * from c "🍒" natural join b "🍌" natural join a "🍏" ;
LOG:  pg_hint_plan[qno=0x1e]: post_parse_analyze_hook: hints from table: "Leading( ( ("🍏" "🍌") "🍒" ) ) HashJoin( "🍏" "🍌" ) HashJoin("🍏" "🍌" "🍒") SeqScan("🍏") IndexOnlyScan("🍌") SeqScan("🍒")": normalized_query="select * from c "🍒" natural join b "🍌" natural join a "🍏" ;", application name ="psql"
LOG:  pg_hint_plan[qno=0x1c]: planner
LOG:  pg_hint_plan[qno=0x1c]: setup_hint_enforcement index deletion: relation=16659(c), inhparent=0, current_hint_state=0xe094648, hint_inhibit_level=0, scanmask=0x1
LOG:  pg_hint_plan[qno=0x1c]: setup_hint_enforcement index deletion: relation=16654(b), inhparent=0, current_hint_state=0xe094648, hint_inhibit_level=0, scanmask=0x12
LOG:  pg_hint_plan[qno=0x1c]: setup_hint_enforcement index deletion: relation=16649(a), inhparent=0, current_hint_state=0xe094648, hint_inhibit_level=0, scanmask=0x1
LOG:  pg_hint_plan[qno=0x1c]: HintStateDump: {used hints:IndexOnlyScan(🍌)SeqScan(🍏)SeqScan(🍒)HashJoin(🍌 🍏)HashJoin(🍌 🍏 🍒)Leading(((🍏 🍌) 🍒))}, {not used hints:(none)}, {duplicate hints:(none)}, {error hints:(none)}
 n | x
---+---
(0 rows)

当pg_hint_plan.debug_print=verbose注入的提示pg_hint_plan.enable_hint_table=on在HintStateDump.

原文标题：pg_stat_statements with pg_hint_plan

原文作者：Franck Pachot 

原文链接：https://dev.to/yugabyte/pgstatstatements-with-pghintplan-o1g