MDEV-26768 Spider table crashes the server after the mysql_list_fields()...

MDEV-26768 Spider table crashes the server after the mysql_list_fields() client's call and produces weird result for SHOW FIELDS.

Suppress errors in ha_spider::info() called from mysqld_show_fields()

storage/spider/ha_spider.cc

@@ -1125,7 +1125,8 @@ THR_LOCK_DATA **ha_spider::store_lock(
     if (
       sql_command == SQLCOM_DROP_TABLE ||
       sql_command == SQLCOM_ALTER_TABLE ||
-      sql_command == SQLCOM_SHOW_CREATE
+      sql_command == SQLCOM_SHOW_CREATE ||
+      sql_command == SQLCOM_SHOW_FIELDS
     ) {
       if (
         lock_type == TL_READ_NO_INSERT &&
@@ -8707,7 +8708,8 @@ int ha_spider::info(
             spider_param_table_init_error_interval())
           {
             pthread_mutex_unlock(&share->sts_mutex);
-            if (sql_command == SQLCOM_SHOW_CREATE)
+            if (sql_command == SQLCOM_SHOW_CREATE ||
+                sql_command == SQLCOM_SHOW_FIELDS)
             {
               if (thd->is_error())
               {
@@ -8781,7 +8783,8 @@ int ha_spider::info(
                 share->init_error = TRUE;
                 share->init = TRUE;
               }
-              if (sql_command == SQLCOM_SHOW_CREATE)
+              if (sql_command == SQLCOM_SHOW_CREATE ||
+                  sql_command == SQLCOM_SHOW_FIELDS)
               {
                 if (thd->is_error())
                 {
@@ -8844,7 +8847,8 @@ int ha_spider::info(
                 share->init_error = TRUE;
                 share->init = TRUE;
               }
-              if (sql_command == SQLCOM_SHOW_CREATE)
+              if (sql_command == SQLCOM_SHOW_CREATE ||
+                  sql_command == SQLCOM_SHOW_FIELDS)
               {
                 if (thd->is_error())
                 {
@@ -8873,7 +8877,8 @@ int ha_spider::info(
               if ((error_num = spider_create_sts_thread(share)))
               {
                 pthread_mutex_unlock(&share->sts_mutex);
-                if (sql_command == SQLCOM_SHOW_CREATE)
+                if (sql_command == SQLCOM_SHOW_CREATE ||
+                    sql_command == SQLCOM_SHOW_FIELDS)
                 {
                   if (thd->is_error())
                   {
@@ -8904,7 +8909,8 @@ int ha_spider::info(
     {
       if ((error_num = check_crd()))
       {
-        if (sql_command == SQLCOM_SHOW_CREATE)
+        if (sql_command == SQLCOM_SHOW_CREATE ||
+            sql_command == SQLCOM_SHOW_FIELDS)
         {
           if (thd->is_error())
           {

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

@@ -248,6 +248,15 @@ a	b	date_format(c, '%Y-%m-%d %H:%i:%s')
 8	g	2011-05-05 21:33:30
 9	h	2011-05-05 22:32:10
 DROP TABLE ta_l2;
+connection master_1;
+CREATE TABLE t (c INT) PARTITION BY LIST COLUMNS (c) (PARTITION p DEFAULT ENGINE=SPIDER);
+SHOW FIELDS FROM t;
+Field	Type	Null	Key	Default	Extra
+c	int(11)	YES		NULL	
+SHOW FIELDS FROM t;
+Field	Type	Null	Key	Default	Extra
+c	int(11)	YES		NULL	
+DROP TABLE t;
 
 deinit
 connection master_1;

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

@@ -982,6 +982,13 @@ if ($HAVE_PARTITION)
   }
 }
 
+--connection master_1
+ 
+CREATE TABLE t (c INT) PARTITION BY LIST COLUMNS (c) (PARTITION p DEFAULT ENGINE=SPIDER);
+SHOW FIELDS FROM t;
+SHOW FIELDS FROM t;
+DROP TABLE t;
+
 --echo
 --echo deinit
 --disable_warnings