MDEV-28560 Deprecate spider_buffer_size

The variable, spider_buffer_size, is used nowhere in the MariaDB Community Server.

storage/spider/mysql-test/spider/r/variable_deprecation.result

@@ -181,6 +181,21 @@ Warnings:
 Warning	1287	The table parameter 'crd_weight' is deprecated and will be removed in a future release
 DROP TABLE tbl_a;
 DROP TABLE tbl_b;
+# MDEV-28560 Deprecate spider_buffer_size
+SET spider_buffer_size = 1;
+Warnings:
+Warning	1287	'@@spider_buffer_size' is deprecated and will be removed in a future release
+SHOW VARIABLES LIKE "spider_buffer_size";
+Variable_name	Value
+spider_buffer_size	1
+CREATE TABLE tbl_a (a INT) ENGINE=Spider COMMENT='bfz "1"';
+Warnings:
+Warning	1287	The table parameter 'bfz' is deprecated and will be removed in a future release
+CREATE TABLE tbl_b (a INT) ENGINE=Spider COMMENT='buffer_size "1"';
+Warnings:
+Warning	1287	The table parameter 'buffer_size' is deprecated and will be removed in a future release
+DROP TABLE tbl_a;
+DROP TABLE tbl_b;
 DROP DATABASE auto_test_local;
 for master_1
 for child2

storage/spider/mysql-test/spider/t/variable_deprecation.test

@@ -108,6 +108,15 @@ eval CREATE TABLE tbl_b (a INT) $MASTER_1_ENGINE COMMENT='crd_weight "1"';
 DROP TABLE tbl_a;
 DROP TABLE tbl_b;
 
+--echo # MDEV-28560 Deprecate spider_buffer_size
+SET spider_buffer_size = 1;
+SHOW VARIABLES LIKE "spider_buffer_size";
+eval CREATE TABLE tbl_a (a INT) $MASTER_1_ENGINE COMMENT='bfz "1"';
+eval CREATE TABLE tbl_b (a INT) $MASTER_1_ENGINE COMMENT='buffer_size "1"';
+
+DROP TABLE tbl_a;
+DROP TABLE tbl_b;
+
 DROP DATABASE auto_test_local;
 
 --disable_query_log

storage/spider/spd_param.cc

@@ -1073,7 +1073,7 @@ int spider_param_bulk_update_size(
  */
 static MYSQL_THDVAR_INT(
   buffer_size, /* name */
-  PLUGIN_VAR_RQCMDARG, /* opt */
+  PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_DEPRECATED, /* opt */
   "Buffer size", /* comment */
   NULL, /* check */
   spider_use_table_value_deprecated, /* update */

storage/spider/spd_table.cc

@@ -2319,6 +2319,7 @@ int spider_parse_connect_info(
 #ifdef HA_CAN_BULK_ACCESS
           SPIDER_PARAM_INT_WITH_MAX("baf", bulk_access_free, 0, 1);
 #endif
+          SPIDER_PARAM_DEPRECATED_WARNING("bfz");
           SPIDER_PARAM_INT("bfz", buffer_size, 0);
 #ifndef WITHOUT_SPIDER_BG_SEARCH
           SPIDER_PARAM_LONGLONG("bfr", bgs_first_read, 0);
@@ -2547,6 +2548,7 @@ int spider_parse_connect_info(
           SPIDER_PARAM_LONG_LIST_WITH_MAX("use_hs_read", use_hs_reads, 0, 1);
 #endif
           SPIDER_PARAM_INT_WITH_MAX("casual_read", casual_read, 0, 63);
+          SPIDER_PARAM_DEPRECATED_WARNING("buffer_size");
           SPIDER_PARAM_INT("buffer_size", buffer_size, 0);
           error_num = connect_string_parse.print_param_error();
           goto error;