old pg_prewarm is very slow when use "ReadBufferExtended" , so use polar_bulk_read_buffer_extended.

NOTICE

@@ -1,6 +1,6 @@
 PolarDB for PostgreSQL
 
-Copyright (c) 2020, Alibaba Group Holding Limited
+Copyright (c) 2021-2022, Alibaba Group Holding Limited
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.

contrib/pg_prewarm/pg_prewarm.c

@@ -192,7 +192,11 @@ pg_prewarm(PG_FUNCTION_ARGS)
 			Buffer		buf;
 
 			CHECK_FOR_INTERRUPTS();
-			buf = ReadBufferExtended(rel, forkNumber, block, RBM_NORMAL, NULL);
+			//buf = ReadBufferExtended(rel, forkNumber, block, RBM_NORMAL, NULL);
+			buf = polar_bulk_read_buffer_extended(rel, MAIN_FORKNUM, block,
+														RBM_NORMAL, NULL,
+														64);
+
 			ReleaseBuffer(buf);
 			++blocks_done;
 		}