環境描述:

作業系統: CentOS Linux release 7.6.1810 (Core)

postgresql版本 postgres (PostgreSQL) 12.4

host1 192.168.112.200

host2 192.168.112.201

首先翻看 postgresql(12.4) 官方文件 (Part VI.Reference => PostgreSQL Client Applications =>psql) 的定義部分

也可以參考 postgresql(12.4) 的原始碼 src/bin/psql/help.c 檔案中 usage 的函式部分

或者執行 psql --help

[postgres@pg1 ~]$ psql --help

psql is the PostgreSQL interactive terminal.

Usage:

psql [OPTION]... [DBNAME [USERNAME]]

General options:

-c, --command=COMMAND run only single command (SQL or internal) and exit

-d, --dbname=DBNAME database name to connect to (default: "postgres")

-f, --file=FILENAME execute commands from file, then exit

-l, --list list available databases, then exit

-v, --set=, --variable=NAME=VALUE

set psql variable NAME to VALUE

(e.g., -v >

-V, --version output version information, then exit

-X, --no-psqlrc do not read startup file (~/.psqlrc)

-1 ("one"), --single-transaction

execute as a single transaction (if non-interactive)

-?, --help[=options] show this help, then exit

--help=commands list backslash commands, then exit

--help=variables list special variables, then exit

Input and output options:

-a, --echo-all echo all input from script

-b, --echo-errors echo failed commands

-e, --echo-queries echo commands sent to server

-E, --echo-hidden display queries that internal commands generate

-L, --log-file=FILENAME send session log to file

-n, --no-readline disable enhanced command line editing (readline)

-o, --output=FILENAME send query results to file (or |pipe)

-q, --quiet run quietly (no messages, only query output)

-s, --single-step single-step mode (confirm each query)

-S, --single-line single-line mode (end of line terminates SQL command)

Output format options:

-A, --no-align unaligned table output mode

--csv CSV (Comma-Separated Values) table output mode

-F, --field-separator=STRING

field separator for unaligned output (default: "|")

-H, --html HTML table output mode

-P, --pset=VAR[=ARG] set printing option VAR to ARG (see \pset command)

-R, --record-separator=STRING

record separator for unaligned output (default: newline)

-t, --tuples-only print rows only

-T, --table-attr=TEXT set HTML table tag attributes (e.g., width, border)

-x, --expanded turn on expanded table output

-z, --field-separator-zero

set field separator for unaligned output to zero byte

-0, --record-separator-zero

set record separator for unaligned output to zero byte

Connection options:

-h, --host=HOSTNAME database server host or socket directory (default: "local socket")

-p, --port=PORT database server port (default: "5432")

-U, --username=USERNAME database user name (default: "postgres")

-w, --no-password never prompt for password

-W, --password force password prompt (should happen automatically)

For more information, type "\?" (for internal commands) or "\help" (for SQL

commands) from within psql, or consult the psql section in the PostgreSQL

documentation.

sql命令與元命令的區別在官方文件 (Part VI.Reference => PostgreSQL Client Applications =>psql) 中的 Entering SQL Commands 與 Meta-Commands 進行描述

1.\x 設定查詢結果輸出

設定前:

postgres=# select * from test;

id

-----

123

(1 row)

設定後:

postgres=# \x

Expanded display is on.

postgres=# select * from test;

-[ RECORD 1 ]

id | 123

2.\timing 顯示執行時間

設定前:

postgres=# select * from test;

id

-----

123

(1 row)

設定後:

postgres=# \timing on

Timing is on.

postgres=# select * from test;

id

-----

123

(1 row)

Time: 0.221 ms

3.\watch反覆執行當前SQL

postgres=# select * from test;

id

-----

123

(1 row)

postgres=# \watch

Thu 21 Jan 2021 05:01:44 AM EST (every 2s)

id

-----

123

(1 row)

Thu 21 Jan 2021 05:01:46 AM EST (every 2s)

id

-----

123

(1 row)

4.-E 獲取元命令對應的SQL語句

使用前:

[postgres@pg1 ~]$ psql

psql (12.4)

Type "help" for help.

postgres=# \d

List of relations

Schema | Name | Type | Owner

--------+------+-------+--------

public | test | table | SYSTEM

(1 row)

使用後:

[postgres@pg1 ~]$ psql -E

psql (12.4)

Type "help" for help.

postgres=# \d

********* QUERY **********

SELECT n.nspname as "Schema",

c.relname as "Name",

CASE c.relkind WHEN 'r' THEN 'table' WHEN 'v' THEN 'view' WHEN 'm' THEN 'materialized view' WHEN 'i' THEN 'index' WHEN 'S' THEN 'sequence' WHEN 's' THEN 'special' WHEN 'f' THEN 'foreign table' WHEN 'p' THEN 'partitioned table' WHEN 'I' THEN 'partitioned index' END as "Type",

pg_catalog.pg_get_userbyid(c.relowner) as "Owner"

FROM pg_catalog.pg_class c

LEFT JOIN pg_catalog.pg_namespace n ON n.oid = c.relnamespace

WHERE c.relkind IN ('r','p','v','m','S','f','')

AND n.nspname <> 'pg_catalog'

AND n.nspname <> 'information_schema'

AND n.nspname !~ '^pg_toast'

AND pg_catalog.pg_table_is_visible(c.oid)

ORDER BY 1,2;

**************************

List of relations

Schema | Name | Type | Owner

--------+------+-------+--------

public | test | table | SYSTEM

(1 row)

5. -c psql執行SQL指令碼

效果:

[postgres@pg1 ~]$ psql -c "select * from test"

id

-----

123

(1 row)

6.-A 設定非對其模式輸出

設定前:

[postgres@pg1 ~]$ psql -c "select * from test"

id

-----

123

(1 row)

設定後:

[postgres@pg1 ~]$ psql -A -c "select * from test"

id

123

(1 row)

7.-t 只顯示記錄資料

設定前:

[postgres@pg1 ~]$ psql -c "select id from test";

id

-----

123

(1 row)

設定後:

[postgres@pg1 ~]$ psql -t -c "select id from test";

123

備註: psql -tA -c "select id from test"; -tA的寫法對後期編寫shell指令碼進行維護幫助極大,以及對監控工具(比如zabbix,請關注後期更新)極其友好.

8. \set 元命令傳遞變數

postgres=# \set v_id 123

postgres=# select * from test where id = :v_id;

id

-----

123

(1 row)

使用psql 定製日常維護指令碼

編輯 .psqlrc 檔案或者 pg_config --sysconfdir 目錄下的 psqlrc 檔案 (postgresql原始碼檔案 src/bin/psql/psqlrc.sample 檔案內容)

\set active_session 'select pid,usename,datname,query,client_addr from pg_stat_activity where pid <> pg_backend_pid() and state = \'active\' order by query';

\set wait_event 'select pid,usename,datname,query_start,client_addr,wait_event_type,wait_event from pg_stat_activity where pid <> pg_backend_pid() and wait_event is not null order by wait_event_type';

\set connections 'select datname,usename,client_addr,count(*) from pg_stat_activity where pid <> pg_backend_pid() group by 1,2,3 order by 1,2,4 desc';

1.查詢活動會話

postgres=# :active_session

pid | usename | datname | query | client_addr

-----+---------+---------+-------+-------------

(0 rows)

2.查詢等待事件

postgres=# :wait_event

------+---------+---------+-------------+-------------+-----------------+---------------------

(5 rows)

3.檢視資料庫連線數

postgres=# :connections

datname | usename | client_addr | count

---------+---------+-------------+-------

| SYSTEM | | 1

| | | 4

(2 rows)

PSQL基本使用(定製維護指令碼)

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