fix(pgmq): replace drop_queue function if exists

We introduced a patch to override pgmq.drop_queue(TEXT) to conditionally
drop objects only if they are part of the extension in `ansible/ansible/files/postgresql_extension_custom_scripts/pgmq/after-create.sql`
. This script might have been installed on installations with existing 1.4.4 extensions.

When the user tries to upgrade pgmq from 1.4.4 to 1.5.1, the upgrade
process will fail because the upgrade script doesn't expect
`pgmq.drop_queue(TEXT)` to exist.

This change introduce the a patch to the pgmq extension to use
`CREATE OR REPLACE FUNCTION` instead of `CREATE FUNCTION` for
`pgmq.drop_queue(TEXT)` in the upgrade script from 1.4.5 to 1.5.0.

Author: jfroche

nix/ext/pgmq/0001-fix-replace-drop_queue-function-if-exists.patch

@@ -0,0 +1,29 @@
+From 31a9b2d736d8a85f113d592754f4832a0097bb2d Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Jean-Fran=C3=A7ois=20Roche?= <[email protected]>
+Date: Thu, 9 Oct 2025 10:53:50 +0200
+Subject: [PATCH] fix: replace drop_queue function if exists
+
+Function drop_queue might have been created by running `postgresql_extension_custom_scripts/pgmq/after-create.sql`
+on a previous version of the extension. In that case, running the migration script will fail because the function already exists.
+
+We use `CREATE OR REPLACE FUNCTION` to avoid that issue.
+---
+ pgmq-extension/sql/pgmq--1.4.5--1.5.0.sql | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/pgmq-extension/sql/pgmq--1.4.5--1.5.0.sql b/pgmq-extension/sql/pgmq--1.4.5--1.5.0.sql
+index 5754eed..de03788 100644
+--- a/pgmq-extension/sql/pgmq--1.4.5--1.5.0.sql
++++ b/pgmq-extension/sql/pgmq--1.4.5--1.5.0.sql
+@@ -122,7 +122,7 @@ BEGIN
+ END;
+ $$ LANGUAGE plpgsql;
+ 
+-CREATE FUNCTION pgmq.drop_queue(queue_name TEXT)
++CREATE OR REPLACE FUNCTION pgmq.drop_queue(queue_name TEXT)
+ RETURNS BOOLEAN AS $$
+ DECLARE
+     qtable TEXT := pgmq.format_table_name(queue_name, 'q');
+-- 
+2.51.0
+

nix/ext/pgmq.nix renamed to nix/ext/pgmq/default.nix

@@ -9,7 +9,7 @@ let
   pname = "pgmq";
 
   # Load version configuration from external file
-  allVersions = (builtins.fromJSON (builtins.readFile ./versions.json)).${pname};
+  allVersions = (builtins.fromJSON (builtins.readFile ../versions.json)).${pname};
 
   # Filter versions compatible with current PostgreSQL version
   supportedVersions = lib.filterAttrs (
@@ -37,6 +37,10 @@ let
         inherit hash;
       };
 
+      patches = lib.optionals (version == latestVersion) [
+        ./0001-fix-replace-drop_queue-function-if-exists.patch
+      ];
+
       buildPhase = ''
         cd pgmq-extension
       '';

nix/packages/postgres.nix

@@ -22,7 +22,7 @@
         ../ext/pgroonga.nix
         ../ext/index_advisor.nix
         ../ext/wal2json.nix
-        ../ext/pgmq.nix
+        ../ext/pgmq
         ../ext/pg_repack.nix
         ../ext/pg-safeupdate.nix
         ../ext/plpgsql-check.nix