default_transaction_read_only

• 17
• 16
• 15
• 14
• 13
• 12
• 11
• 10
• 9.6
• 9.5
• 9.4
• 9.3
• 9.2
• 9.1
• 9.0
• 8.4
• 8.3
• 8.2

default_transaction_read_only 的基本用法示例

postgres=# SHOW transaction_read_only;
 transaction_read_only 
-----------------------
 off
(1 row)

postgres=# BEGIN;
BEGIN

postgres=*# SET TRANSACTION READ ONLY;
SET

postgres=*# SHOW transaction_read_only;
 transaction_read_only 
-----------------------
 on
(1 row)

这等效于（在主服务器上）

postgres=# BEGIN ;
BEGIN

postgres=*# SET transaction_read_only = on;
SET

postgres=*# SHOW transaction_read_only;
 transaction_read_only 
-----------------------
 on
(1 row)

postgres=*# INSERT INTO foo values(1);
ERROR:  cannot execute INSERT in a read-only transaction

在备用服务器上，default_transaction_read_only 始终为 on

postgres=# SELECT pg_is_in_recovery();
 pg_is_in_recovery 
-------------------
 t
(1 row)

postgres=# SHOW transaction_read_only;
 transaction_read_only 
-----------------------
 on
(1 row)

无法在备用服务器上设置 default_transaction_read_only

postgres=# SET transaction_read_only = off;
ERROR:  cannot set transaction read-write mode during recovery

• PostgreSQL 文档： default_transaction_read_only