Message-ID: <6723c612.050a0220.1567f4.b94a@mx.google.com>
Sender: Michael Banck <mbanck@gmail.com>
Date: Thu, 31 Oct 2024 19:01:54 +0100
From: Michael Banck <mbanck@gmx.net>
To: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Subject: [PATCH] Add support for displaying database service in psql prompt
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Hi,

I think it might be useful to sometimes display the database service
(i.e. what is defined in ~/.pg_service.conf and used via psql
service=foo) in the psql prompt, e.g. if you have 'test' and 'prod'
services, but both have the same database name. This was also suggested
to me during a recent customer training.

I chose the '%s' tag for it. I had to add the service to PGConn as
PQservice (first patch) to libpq and then use it in psql in the second
patch.


Michael

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 filename="v1-0001-Add-PQservice-to-PGConn.patch"

From f876195acb797a5ac58c17409fdd75d18581c292 Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.banck@credativ.de>
Date: Thu, 31 Oct 2024 18:27:52 +0100
Subject: [PATCH v1 1/2] Add PQservice to PGConn.

This adds the content of the database service (if any) to PGConn. One
use for this would be for psql to display the service as part of the
prompt.
---
 src/interfaces/libpq/exports.txt  |  1 +
 src/interfaces/libpq/fe-connect.c | 11 ++++++++++-
 src/interfaces/libpq/libpq-fe.h   |  1 +
 src/interfaces/libpq/libpq-int.h  |  1 +
 4 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt
index 5d8213e0b5..2ad2cbf5ca 100644
--- a/src/interfaces/libpq/exports.txt
+++ b/src/interfaces/libpq/exports.txt
@@ -205,3 +205,4 @@ PQcancelFinish            202
 PQsocketPoll              203
 PQsetChunkedRowsMode      204
 PQgetCurrentTimeUSec      205
+PQservice                 206
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 61c025ff3b..8d809ee4cb 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -190,7 +190,8 @@ typedef struct _internalPQconninfoOption
 
 static const internalPQconninfoOption PQconninfoOptions[] = {
 	{"service", "PGSERVICE", NULL, NULL,
-	"Database-Service", "", 20, -1},
+		"Database-Service", "", 20,
+	offsetof(struct pg_conn, pgservice)},
 
 	{"user", "PGUSER", NULL, NULL,
 		"Database-User", "", 20,
@@ -7052,6 +7053,14 @@ PQdb(const PGconn *conn)
 	return conn->dbName;
 }
 
+char *
+PQservice(const PGconn *conn)
+{
+	if (!conn)
+		return NULL;
+	return conn->pgservice;
+}
+
 char *
 PQuser(const PGconn *conn)
 {
diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h
index 15012c770c..5947e7c766 100644
--- a/src/interfaces/libpq/libpq-fe.h
+++ b/src/interfaces/libpq/libpq-fe.h
@@ -385,6 +385,7 @@ extern int	PQrequestCancel(PGconn *conn);
 
 /* Accessor functions for PGconn objects */
 extern char *PQdb(const PGconn *conn);
+extern char *PQservice(const PGconn *conn);
 extern char *PQuser(const PGconn *conn);
 extern char *PQpass(const PGconn *conn);
 extern char *PQhost(const PGconn *conn);
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 08cc391cbd..dcebca9898 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -394,6 +394,7 @@ struct pg_conn
 	char	   *fbappname;		/* fallback application name */
 	char	   *dbName;			/* database name */
 	char	   *replication;	/* connect as the replication standby? */
+	char	   *pgservice;		/* Postgres service, if any */
 	char	   *pguser;			/* Postgres username and password, if any */
 	char	   *pgpass;
 	char	   *pgpassfile;		/* path to a file containing password(s) */
-- 
2.39.5


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 filename="v1-0002-Add-support-for-database-service-to-psql-prompt.patch"

From 3257e93d20353ff348b15df9b45207ec45839ed5 Mon Sep 17 00:00:00 2001
From: Michael Banck <michael.banck@credativ.de>
Date: Thu, 31 Oct 2024 18:49:14 +0100
Subject: [PATCH v1 2/2] Add support for database service to psql prompt.

This adds a new psql variable SERVICE as well as the string '%s' for the
psql PROMPT, displaying the service (from PGSERVICEFILE) if so desired.
---
 src/bin/psql/command.c | 2 ++
 src/bin/psql/prompt.c  | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 328d78c73f..e8f2573649 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -4085,6 +4085,7 @@ SyncVariables(void)
 	pset.sversion = PQserverVersion(pset.db);
 
 	SetVariable(pset.vars, "DBNAME", PQdb(pset.db));
+	SetVariable(pset.vars, "SERVICE", PQservice(pset.db));
 	SetVariable(pset.vars, "USER", PQuser(pset.db));
 	SetVariable(pset.vars, "HOST", PQhost(pset.db));
 	SetVariable(pset.vars, "PORT", PQport(pset.db));
@@ -4118,6 +4119,7 @@ void
 UnsyncVariables(void)
 {
 	SetVariable(pset.vars, "DBNAME", NULL);
+	SetVariable(pset.vars, "SERVICE", NULL);
 	SetVariable(pset.vars, "USER", NULL);
 	SetVariable(pset.vars, "HOST", NULL);
 	SetVariable(pset.vars, "PORT", NULL);
diff --git a/src/bin/psql/prompt.c b/src/bin/psql/prompt.c
index 0d99d00ac9..de3d976103 100644
--- a/src/bin/psql/prompt.c
+++ b/src/bin/psql/prompt.c
@@ -33,6 +33,7 @@
  * %p - backend pid
  * %> - database server port number
  * %n - database user name
+ * %s - service
  * %/ - current database
  * %~ - like %/ but "~" when database name equals user name
  * %w - whitespace of the same width as the most recent output of PROMPT1
@@ -246,6 +247,11 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
 						}
 					break;
 
+				case 's':
+					if (PQservice(pset.db))
+						strlcpy(buf, PQservice(pset.db), sizeof(buf));
+					break;
+
 				case 'l':
 					snprintf(buf, sizeof(buf), UINT64_FORMAT, pset.stmt_lineno);
 					break;
-- 
2.39.5


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