Add ParameterDescription message to libpq frontend long message types

Ning Sun <classicning@gmail.com>

From: Ning Sun <classicning@gmail.com>

To: pgsql-hackers@postgresql.org

Date: 2026-04-01T06:32:17Z

Lists: pgsql-hackers

Attachments

0001-add-ParameterDescription-to-long-message-types.patch (text/x-patch) patch 0001

Hi,

I'm maintaining a Rust library pgwire to implement postgres wire 
protocol in rust. While doing a corner case test, I noticed the 
inconsistency for ParameterDescription between backend and frontend.

The backend allows up to 65535 parameters in a prepared statement. But 
when running Describe on the statement, there is a size limit of 30000 
bytes for ParameterDescription on the frontend. This means we can only 
describe statements with at most ~7500 parameters. For statements exceed 
the limit, it ends up with error about the message size.

This patch simply adds ParameterDescription to VALID_LONG_MESSAGE_TYPE 
whitelist to remove the cap.

Commits

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

Fix PQdescribePrepared with more than 7498 params
- 1b79c8d1a581 14 (unreleased) landed
- 0f63b74a4730 15 (unreleased) landed
- 8d516d2b99b3 16 (unreleased) landed
- e4183c667d86 17 (unreleased) landed
- b1ab4bc52a1f 18 (unreleased) landed
- e0511883cae2 19 (unreleased) landed