Horton

Re: display hot standby state in psql prompt

Jim Jones <jim.jones@uni-muenster.de>

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From: Jim Jones <jim.jones@uni-muenster.de>
To: Fujii Masao <masao.fujii@gmail.com>
Cc: Andreas Karlsson <andreas@proxel.se>, Nathan Bossart <nathandbossart@gmail.com>, Srinath Reddy Sadipiralla <srinath2133@gmail.com>, Greg Sabino Mullane <htamfids@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Chao Li <li.evan.chao@gmail.com>
Date: 2025-11-10T08:14:49Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. psql: Add %i prompt escape to indicate hot standby status.

  2. Mark search_path as GUC_REPORT


On 10/11/2025 08:30, Fujii Masao wrote:
> If the main goal of this feature is to help users easily determine
> whether they're connected to a primary or a standby,
> seems simply showing whether the server is in hot standby
> should be sufficient. I'm not sure how useful it would be in practice
> to show information based on default_transaction_read_only or
> transaction_read_only.

This "primary" or "standby" approach was actually the initial proposal,
but it evolved after a few reviews. Extending it to use
transaction_read_only and default_transaction_read_only adds real value
to the feature, but doing so requires either:

1. Marking transaction_read_only as GUC_REPORT (controversial and
rejected in the past), or
2. Querying transaction_read_only with SHOW every time the prompt is
displayed within a transaction block (IMO minimal overhead -- but
unconventional?).

Although I lean toward the initial proposal, I can totally live with
either approach, since both would be able to distinguish if a server is
in hot standby or not.

Should we switch back to the initial proposal?

Thanks!

Best, Jim