MDEV-33008 Fix spider table discovery

A new column was introduced to the show index output in 10.6 in
f691d986

Thus we update the check of the number of columns to be at least 13,
rather than exactly 13.

Also backport an err number and format from 10.5 for better error
messages when the column number is wrong.

storage/spider/mysql-test/spider/bugfix/r/mdev_33008.result

+for master_1
+for child2
+for child3
+set spider_same_server_link=on;
+CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t2 (
+`id` int(11) NOT NULL AUTO_INCREMENT,
+`code` varchar(10) DEFAULT NULL,
+PRIMARY KEY (`id`)
+);
+create table t1 ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `code` varchar(10) DEFAULT NULL,
+  PRIMARY KEY (`id`)
+) ENGINE=SPIDER DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"'
+drop table t1, t2;
+drop server srv;
+for master_1
+for child2
+for child3

storage/spider/mysql-test/spider/bugfix/t/mdev_33008.test

+--disable_query_log
+--disable_result_log
+--source ../../t/test_init.inc
+--enable_result_log
+--enable_query_log
+set spider_same_server_link=on;
+evalp CREATE SERVER srv FOREIGN DATA WRAPPER mysql
+OPTIONS (SOCKET "$MASTER_1_MYSOCK", DATABASE 'test',user 'root');
+create table t2 (
+  `id` int(11) NOT NULL AUTO_INCREMENT,
+  `code` varchar(10) DEFAULT NULL,
+  PRIMARY KEY (`id`)
+);
+create table t1 ENGINE=Spider
+COMMENT='WRAPPER "mysql", srv "srv",TABLE "t2"';
+show create table t1;
+drop table t1, t2;
+
+drop server srv;
+--disable_query_log
+--disable_result_log
+--source ../../t/test_deinit.inc
+--enable_result_log
+--enable_query_log

storage/spider/spd_db_mysql.cc

@@ -1566,10 +1566,13 @@ int spider_db_mbase_result::fetch_index_for_discover_table_structure(
     }
     DBUG_RETURN(0);
   }
-  if (num_fields() != 13)
+  if (num_fields() < 13)
   {
-    DBUG_PRINT("info",("spider num_fields != 13"));
-    my_printf_error(ER_SPIDER_UNKNOWN_NUM, ER_SPIDER_UNKNOWN_STR, MYF(0));
+    DBUG_PRINT("info",("spider num_fields < 13"));
+    my_printf_error(ER_SPIDER_CANT_NUM, ER_SPIDER_CANT_STR1, MYF(0),
+                    "fetch index for table structure discovery because of "
+                    "wrong number of columns in SHOW INDEX FROM output: ",
+                    num_fields());
     DBUG_RETURN(ER_SPIDER_UNKNOWN_NUM);
   }
   bool first = TRUE;

storage/spider/spd_err.h

@@ -127,6 +127,8 @@
 #define ER_SPIDER_SAME_SERVER_LINK_NUM 12720
 #define ER_SPIDER_SAME_SERVER_LINK_STR1 "Host:%s and Socket:%s aim self server. Please change spider_same_server_link parameter if this link is required."
 #define ER_SPIDER_SAME_SERVER_LINK_STR2 "Host:%s and Port:%ld aim self server. Please change spider_same_server_link parameter if this link is required."
+#define ER_SPIDER_CANT_NUM 12721
+#define ER_SPIDER_CANT_STR1 "Can't %s%d"
 #define ER_SPIDER_COND_SKIP_NUM 12801
 
 #define ER_SPIDER_UNKNOWN_NUM 12500