Add pg_checkpointer predefined role for CHECKPOINT command.

Any user with the privileges of pg_checkpointer can issue a CHECKPOINT
command.

Reviewed-by: Stephen Frost
Discussion: https://postgr.es/m/67a1d667e8ec228b5e07f232184c80348c5d93f4.camel%40j-davis.com

src/backend/tcop/utility.c

@@ -24,6 +24,7 @@
 #include "catalog/catalog.h"
 #include "catalog/index.h"
 #include "catalog/namespace.h"
+#include "catalog/pg_authid.h"
 #include "catalog/pg_inherits.h"
 #include "catalog/toasting.h"
 #include "commands/alter.h"
@@ -939,10 +940,10 @@ standard_ProcessUtility(PlannedStmt *pstmt,
 			break;
 
 		case T_CheckPointStmt:
-			if (!superuser())
+			if (!has_privs_of_role(GetUserId(), ROLE_PG_CHECKPOINTER))
 				ereport(ERROR,
 						(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
-						 errmsg("must be superuser to do CHECKPOINT")));
+						 errmsg("must be superuser or have privileges of pg_checkpointer to do CHECKPOINT")));
 
 			RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_WAIT |
 							  (RecoveryInProgress() ? 0 : CHECKPOINT_FORCE));

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202110272
+#define CATALOG_VERSION_NO	202111091
 
 #endif

src/include/catalog/pg_authid.dat

@@ -79,5 +79,10 @@
   rolcreaterole => 'f', rolcreatedb => 'f', rolcanlogin => 'f',
   rolreplication => 'f', rolbypassrls => 'f', rolconnlimit => '-1',
   rolpassword => '_null_', rolvaliduntil => '_null_' },
+{ oid => '4544', oid_symbol => 'ROLE_PG_CHECKPOINTER',
+  rolname => 'pg_checkpointer', rolsuper => 'f', rolinherit => 't',
+  rolcreaterole => 'f', rolcreatedb => 'f', rolcanlogin => 'f',
+  rolreplication => 'f', rolbypassrls => 'f', rolconnlimit => '-1',
+  rolpassword => '_null_', rolvaliduntil => '_null_' },
 
 ]