[@TOC]
# 作用:
决定 pg_stat_activity.query 的长度
> 期望能控制 pg_stat_statements.query 的长度, 实际测试并不能影响其长度
```sql
test=# select * from pg_settings where name='track_activity_query_size';
-[ RECORD 1 ]---+-------------------------------------------------------------
name | track_activity_query_size
setting | 1024
unit | B
category | Statistics / Query and Index Statistics Collector
short_desc | Sets the size reserved for pg_stat_activity.query, in bytes.
extra_desc |
context | postmaster
vartype | integer
source | default
min_val | 100
max_val | 1048576
enumvals |
boot_val | 1024
reset_val | 1024
sourcefile |
sourceline |
pending_restart | f
test=# alter system set track_activity_query_size to '10';
ERROR: 10 B is outside the valid range for parameter "track_activity_query_size" (100 .. 1048576)
test=# alter system set track_activity_query_size to '100';
ALTER SYSTEM
test=# \q
postgres@d8b3cfb2eab2:~/14/pgdata$ pg_ctl restart
waiting for server to shut down.... done
server stopped
waiting for server to start....2023-12-30 10:48:38.794 UTC [135] LOG: redirecting log output to logging collector process
2023-12-30 10:48:38.794 UTC [135] HINT: Future log output will appear in directory "log".
done
server started
postgres@d8b3cfb2eab2:~/14/pgdata$ psql
psql (14.10 (Debian 14.10-1.pgdg110+1))
Type "help" for help.
postgres=# show track_activity_query_size ;
track_activity_query_size
---------------------------
100B
(1 row)
```
提前安装了 pg_stat_statements 插件
# 会话 1
````sql
create table test(id bigserial primary key, name text);
test=# begin;
BEGIN
test=*# insert into test (name ) values('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name'),('name');
INSERT 0 25
````
# 会话 2
```sql
postgres=# select length(query) , * from pg_stat_activity where query like 'insert%';
-[ RECORD 1 ]----+----------------------------------------------------------------------------------------------------
length | 99
datid | 16384
datname | test
pid | 148
leader_pid |
usesysid | 10
usename | postgres
application_name | psql
client_addr |
client_hostname |
client_port | -1
backend_start | 2023-12-30 10:48:59.788431+00
xact_start | 2023-12-30 10:55:39.935999+00
query_start | 2023-12-30 10:55:44.180545+00
state_change | 2023-12-30 10:55:44.181013+00
wait_event_type | Client
wait_event | ClientRead
state | idle in transaction
backend_xid | 741
backend_xmin |
query_id | -4687908949149066856
query | insert into test (name ) values('name'),('name'),('name'),('name'),('name'),('name'),('name'),('nam
backend_type | client backend
```
# 会话 1
```sql
test=# \x
Expanded display is on.
test=# select length(query),query from pg_stat_statements where query like 'insert%';
-[ RECORD 1 ]-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
length | 171
query | insert into test (name ) values($1),($2),($3),($4),($5),($6),($7),($8),($9),($10),($11),($12),($13),($14),($15),($16),($17),($18),($19),($20),($21),($22),($23),($24),($25)
```
> 可以看到 即使修改了 track_activity_query_size 并不会影响到 pg_stat_statements.query 的长度
