如何獲得交易中的當前查詢

Question

我試圖從pg_stats_activity獲取當前查詢，但未按預期工作。

外交易一切正常：

pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
(1 row) 

pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 2 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 2 is not null; 
(1 row) 

pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 3 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 3 is not null; 
(1 row) 

但是在一個事務中，我得到錯誤的結果：

pagetest=# begin; 
BEGIN 
pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
(1 row) 

pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 2 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
(1 row) 

pagetest=# select query from pg_stat_activity where pid = pg_backend_pid() and 3 is not null; 
             query           
------------------------------------------------------------------------------------ 
select query from pg_stat_activity where pid = pg_backend_pid() and 1 is not null; 
(1 row) 

pagetest=# rollback 
pagetest-# ; 
ROLLBACK 

它看起來像有在統計收集意見有些奇怪的可見性規則。有沒有合理的方法呢？

Answer 1

試試這個：

BEGIN; 
    select 1,current_query(); 
    select 2,current_query(); 
    ROLLBACK;