Subject: Re: [Patch] ALTER SYSTEM READ ONLY
To: amul sul <sulamul@gmail.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
References: 
 <CAAJ_b97KZzdJsffwRK7w0XU5HnXkcgKgTR69t8cOZztsyXjkQw@mail.gmail.com>
From: tushar <tushar.ahuja@enterprisedb.com>
Message-ID: <ec4106f8-8f0e-eda1-202e-037ebd803bdb@enterprisedb.com>
Date: Wed, 17 Jun 2020 19:21:18 +0530
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On 6/16/20 7:25 PM, amul sul wrote:
> Attached patch proposes $Subject feature which forces the system into 
> read-only
> mode where insert write-ahead log will be prohibited until ALTER 
> SYSTEM READ
> WRITE executed.

Thanks Amul.

1) ALTER SYSTEM

postgres=# alter system read only;
ALTER SYSTEM
postgres=# alter  system reset all;
ALTER SYSTEM
postgres=# create table t1(n int);
ERROR:  cannot execute CREATE TABLE in a read-only transaction

Initially i thought after firing 'Alter system reset all' , it will be 
back to  normal.

can't we have a syntax like - "Alter system set read_only='True' ; "

so that ALTER SYSTEM command syntax should be same for all.

postgres=# \h alter system
Command:     ALTER SYSTEM
Description: change a server configuration parameter
Syntax:
ALTER SYSTEM SET configuration_parameter { TO | = } { value | 'value' | 
DEFAULT }

ALTER SYSTEM RESET configuration_parameter
ALTER SYSTEM RESET ALL

How we are going to justify this in help command of ALTER SYSTEM ?

2)When i connected to postgres in a single user mode , i was not able to 
set the system in read only

[edb@tushar-ldap-docker bin]$ ./postgres --single -D data postgres


PostgreSQL stand-alone backend 14devel
backend> alter system read only;
ERROR:  checkpointer is not running

backend>

-- 
regards,tushar
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