!4514 【同步】修复最大可用模式某些场景不生效的问题

Merge pull request !4514 from 胡正超/master

src/gausskernel/process/postmaster/checkpointer.cpp

@@ -397,7 +397,7 @@ void CheckpointerMain(void)
             u_sess->attr.attr_storage.CheckPointTimeout = ENABLE_INCRE_CKPT
                                                               ? u_sess->attr.attr_storage.incrCheckPointTimeout
                                                               : u_sess->attr.attr_storage.fullCheckPointTimeout;
-
+            most_available_sync = (volatile bool) u_sess->attr.attr_storage.guc_most_available_sync;
             /*
              * Checkpointer is the last process to shut down, so we ask it to
              * hold the keys for a range of other tasks required most of which
@@ -740,6 +740,7 @@ void CheckpointWriteDelay(int flags, double progress)
         if (t_thrd.checkpoint_cxt.got_SIGHUP) {
             t_thrd.checkpoint_cxt.got_SIGHUP = false;
             ProcessConfigFile(PGC_SIGHUP);
+            most_available_sync = (volatile bool)u_sess->attr.attr_storage.guc_most_available_sync;
             /* update shmem copies of config variables */
             UpdateSharedMemoryConfig();
         }

src/gausskernel/storage/replication/syncrep.cpp

@@ -1130,6 +1130,9 @@ static void SyncRepGetNthLatestSyncRecPtr(XLogRecPtr* receivePtr, XLogRecPtr* wr
     }
 
     group_len = list_length(stby_list);
+    if (group_len == 0) {
+        return;
+    }
 
     receive_array = (XLogRecPtr*)palloc(sizeof(XLogRecPtr) * group_len);
     write_array = (XLogRecPtr*)palloc(sizeof(XLogRecPtr) * group_len);