Re: display hot standby state in psql prompt

From: Jim Jones <jim(dot)jones(at)uni-muenster(dot)de>
To: Fujii Masao <masao(dot)fujii(at)gmail(dot)com>
Cc: Srinath Reddy Sadipiralla <srinath2133(at)gmail(dot)com>, Greg Sabino Mullane <htamfids(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: display hot standby state in psql prompt
Date: 2025-10-24 16:13:09
Message-ID: c7748940-b2f6-4022-8c80-66dd8304c42e@uni-muenster.de
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On 24/10/2025 17:21, Fujii Masao wrote:
> + const char *hs = PQparameterStatus(pset.db, "in_hot_standby");
> + const char *ro = PQparameterStatus(pset.db, "default_transaction_read_only");
>
> When either hs or ro is NULL, the displayed status can be incorrect.
> For example, connecting to a standby server running PostgreSQL 10
> incorrectly shows "read/write". In such cases, wouldn't it be clearer
> to display something like "unknown", similar to how the "Hot Standby"
> column in \conninfo reports "unknown"?

Oh, it didn't occur to me to test this edge case. Thanks for the hint!

Would this be what you have in mind?

if (!hs || !ro)
strlcpy(buf, "unknown", sizeof(buf));
else if ((hs && strcmp(hs, "on") == 0) ||
(ro && strcmp(ro, "on") == 0))
strlcpy(buf, "read-only", sizeof(buf));
else
strlcpy(buf, "read/write", sizeof(buf));

Best, Jim

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