PostgreSQL 14數據庫監控和日志功能的加強

查詢標識符(query identifier)

查詢標識符用於標識一個查詢，在擴展中可以被交叉引用。在PostgreSQL 14之前，擴展使用一個算法來計算query_id。可以使用相同的算法來計算query_id，但是擴展都使用了自己的算法來計算query_id。在14版本內核提供了query_id，現在的監控擴展和工具，如pg_stat_activity,explain,pg_stat_statments都可以使用這個query_id,而不再自己重新計算。

指定log_line_prefix之后，可以在csvlog中看到query_id。從用戶角度來看，有兩個好處：

1.所有的工具和擴展都使用相同的query_id,便於交叉使用query_id。在此之前，所有的工具和擴展都要使用自己的算法計算query_id。

2.所有的工具和擴展都使用內核計算出的query_id，不再自己單獨計算，有益於提升性能。

通過參數 compute_query_id開啟或關閉query_id的計算，默認值是auto。可以在參數文件中配置，也可以通過set命令配置。

 

pg_stat_activity

set compute_query_id=off;

SELECT datname, query, query_id FROM pg_stat_activity;
 datname  |                                 query                                 | query_id 
----------+-----------------------------------------------------------------------+----------
 postgres | select datname, query, query_id from pg_stat_activity;                |         
 postgres | UPDATE pgbench_branches SET bbalance = bbalance + 2361 WHERE bid = 1; |

set compute_query_id=on;

SELECT datname, query, query_id FROM pg_stat_activity;
 datname  |                                 query                                 |      query_id       
----------+-----------------------------------------------------------------------+---------------------
 postgres | select datname, query, query_id from pg_stat_activity;                |  846165942585941982
 postgres | UPDATE pgbench_tellers SET tbalance = tbalance + 3001 WHERE tid = 44; | 3354982309855590749

 

log

在以前的版本中，內核沒有這種提供query_id的機制。query_id在日志是非常有用的。為此，要配置參數log_line_prefix。“%Q”增加了query_id的功能。例如：

log_line_prefix = 'query_id = [%Q] -> '

query_id = [0] -> LOG:  statement: CREATE PROCEDURE ptestx(OUT a int) LANGUAGE SQL AS $$ INSERT INTO cp_test VALUES (1, 'a') $$;
query_id = [-6788509697256188685] -> ERROR:  return type mismatch in function declared to return record
query_id = [-6788509697256188685] -> DETAIL:  Function's final statement must be SELECT or INSERT/UPDATE/DELETE RETURNING.
query_id = [-6788509697256188685] -> CONTEXT:  SQL function "ptestx"
query_id = [-6788509697256188685] -> STATEMENT:  CREATE PROCEDURE ptestx(OUT a int) LANGUAGE SQL AS $$ INSERT INTO cp_test VALUES (1, 'a') $$;

 

explain

如果開啟了compute_query_id,explain就會顯示query_id。

set compute_query_id=off;

EXPLAIN VERBOSE SELECT * FROM foo;
                          QUERY PLAN                          
--------------------------------------------------------------
​
 Seq Scan on public.foo  (cost=0.00..15.01 rows=1001 width=4)
   Output: a
(2 rows)

set compute_query_id=on;

EXPLAIN VERBOSE SELECT * FROM foo;
                          QUERY PLAN                          
--------------------------------------------------------------
 Seq Scan on public.foo  (cost=0.00..15.01 rows=1001 width=4)
   Output: a
 Query Identifier: 3480779799680626233
(3 rows)

 

autovacuum和auto-analyze日志增強

版本14增強了auto-vacuum和auto-analyze日志功能。現在可以在日志中看到I/O計時功能。顯示了讀和寫花費了多少時間。

automatic vacuum of table "postgres.pg_catalog.pg_depend": index scans: 1
pages: 0 removed, 67 remain, 0 skipped due to pins, 0 skipped frozen
tuples: 89 removed, 8873 remain, 0 are dead but not yet removable, oldest xmin: 210871
index scan needed: 2 pages from table (2.99% of total) had 341 dead item identifiers removed
index "pg_depend_depender_index": pages: 39 in total, 0 newly deleted, 0 currently deleted, 0 reusable
index "pg_depend_reference_index": pages: 41 in total, 0 newly deleted, 0 currently deleted, 0 reusable
​
I/O timings: read: 44.254 ms, write: 0.531 ms
​
avg read rate: 13.191 MB/s, avg write rate: 8.794 MB/s
buffer usage: 167 hits, 126 misses, 84 dirtied
WAL usage: 85 records, 15 full page images, 78064 bytes
system usage: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.07 s

 

連接日志

如果開啟了log_connections/log_disconnections選項，就會記錄建立連接和斷開連接到日志。因此，版本14現在也記錄實際的用戶名。如果使用了外部驗證機制，並在pg_ident.conf定義了映射關系，就很難識別真正的用戶名。在版本14之前，只能看到映射名。

pg_ident.conf

# MAPNAME       SYSTEM-USERNAME         PG-USERNAME
​
pg              vagrant                 postgres

　　

pg_hba.conf

# TYPE  DATABASE        USER            ADDRESS                 METHOD
# "local" is for Unix domain socket connections only
local   all             all                                     peer map=pg

　　

在PostgreSQL-14之前

LOG:  database system was shut down at 2021-11-19 11:24:30 UTC
LOG:  database system is ready to accept connections
LOG:  connection received: host=[local]
LOG:  connection authorized: user=postgres database=postgres application_name=psql

在PostgreSQL-14中

LOG:  database system is ready to accept connections
LOG:  connection received: host=[local]
LOG:  connection authenticated: identity="vagrant" method=peer (/usr/local/pgsql.14/bin/data/pg_hba.conf:89)
LOG:  connection authorized: user=postgres database=postgres application_name=psql