Don't allow to set replication slot_name as ''.

Amit Kapila · Amit Kapila · commit 29abde637bbb · 2021-07-19T10:36:15.000+05:30
We don't allow to create replication slot_name as an empty string ('') via SQL API pg_create_logical_replication_slot() but it is allowed to be set via Alter Subscription command. This will lead to apply worker repeatedly keep trying to stream data via slot_name '' and the user is not allowed to create the slot with that name. Author: Japin Li Reviewed-By: Ranier Vilela, Amit Kapila Backpatch-through: 10, where it was introduced Discussion: https://postgr.es/m/MEYP282MB1669CBD98E721C77CA696499B61A9@MEYP282MB1669.AUSP282.PROD.OUTLOOK.COM
diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
@@ -173,6 +173,8 @@ parse_subscription_options(ParseState *pstate, List *stmt_options,
 			/* Setting slot_name = NONE is treated as no slot name. */
 			if (strcmp(opts->slot_name, "none") == 0)
 				opts->slot_name = NULL;
+			else
+				ReplicationSlotValidateName(opts->slot_name, ERROR);
 		}
 		else if (IsSet(supported_opts, SUBOPT_COPY_DATA) &&
 				 strcmp(defel->defname, "copy_data") == 0)
diff --git a/src/test/regress/expected/subscription.out b/src/test/regress/expected/subscription.out
@@ -86,6 +86,9 @@ ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refr
 ALTER SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist2';
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 -- fail
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = '');
+ERROR:  replication slot name "" is too short
+-- fail
 ALTER SUBSCRIPTION regress_doesnotexist CONNECTION 'dbname=regress_doesnotexist2';
 ERROR:  subscription "regress_doesnotexist" does not exist
 ALTER SUBSCRIPTION regress_testsub SET (create_slot = false);
diff --git a/src/test/regress/sql/subscription.sql b/src/test/regress/sql/subscription.sql
@@ -65,6 +65,9 @@ ALTER SUBSCRIPTION regress_testsub SET PUBLICATION testpub2, testpub3 WITH (refr
 ALTER SUBSCRIPTION regress_testsub CONNECTION 'dbname=regress_doesnotexist2';
 ALTER SUBSCRIPTION regress_testsub SET (slot_name = 'newname');
 
+-- fail
+ALTER SUBSCRIPTION regress_testsub SET (slot_name = '');
+
 -- fail
 ALTER SUBSCRIPTION regress_doesnotexist CONNECTION 'dbname=regress_doesnotexist2';
 ALTER SUBSCRIPTION regress_testsub SET (create_slot = false);

Original file line number	Diff line number	Diff line change
`@@ -173,6 +173,8 @@ parse_subscription_options(ParseState pstate, List stmt_options,`
`173`	`173`	`/* Setting slot_name = NONE is treated as no slot name. */`
`174`	`174`	`if (strcmp(opts->slot_name, "none") == 0)`
`175`	`175`	`opts->slot_name = NULL;`
	`176`	`+ else`
	`177`	`+ ReplicationSlotValidateName(opts->slot_name, ERROR);`
`176`	`178`	`}`
`177`	`179`	`else if (IsSet(supported_opts, SUBOPT_COPY_DATA) &&`
`178`	`180`	`strcmp(defel->defname, "copy_data") == 0)`