MDEV-30170 ha_spider::delete_table() should report table not exist

All Spider tables are recorded in the system table
mysql.spider_tables. Deleting a spider table removes the corresponding
rows from the system table, among other things. This patch makes it so
that if spider could not find any record in the system table to delete
for a given table, it should correctly report that no such Spider
table exists.

storage/spider/ha_spider.cc

@@ -11371,7 +11371,10 @@ int ha_spider::create(
     if (
       thd->lex->create_info.or_replace() &&
       (error_num = spider_delete_tables(
-        table_tables, tmp_share.table_name, &dummy))
+        table_tables, tmp_share.table_name, &dummy)) &&
+      /* In this context, no key found in mysql.spider_tables means
+      the Spider table does not exist */
+      error_num != HA_ERR_KEY_NOT_FOUND
     ) {
       goto error;
     }
@@ -11842,6 +11845,10 @@ int ha_spider::delete_table(
       (error_num = spider_delete_tables(
         table_tables, name, &old_link_count))
     ) {
+      /* In this context, no key found in mysql.spider_tables means
+      the Spider table does not exist */
+      if (error_num == HA_ERR_KEY_NOT_FOUND)
+        error_num= HA_ERR_NO_SUCH_TABLE;
       goto error;
     }
     spider_close_sys_table(current_thd, table_tables,

storage/spider/mysql-test/spider/bugfix/r/mdev_30170.result

+install soname 'ha_spider';
+DROP TABLE non_existing_table;
+ERROR 42S02: Unknown table 'test.non_existing_table'
+create or replace table non_existing_table (c int) engine=Spider;
+drop table non_existing_table;
+Warnings:
+Warning	1620	Plugin is busy and will be uninstalled on shutdown

storage/spider/mysql-test/spider/bugfix/t/mdev_30170.test

+install soname 'ha_spider';
+--error ER_BAD_TABLE_ERROR
+DROP TABLE non_existing_table;
+# Test that create or replace a non existing spider table work
+create or replace table non_existing_table (c int) engine=Spider;
+drop table non_existing_table;
+--disable_query_log
+--source ../../include/clean_up_spider.inc

storage/spider/spd_sys_table.cc

@@ -1865,6 +1865,16 @@ int spider_delete_xa_member(
   DBUG_RETURN(0);
 }
 
+/**
+  Delete a Spider table from mysql.spider_tables.
+
+  @param  table           The table mysql.spider_tables
+  @param  name            The name of the Spider table to delete
+  @param  old_link_count  The number of links in the deleted table
+
+  @retval 0               Success
+  @retval nonzero         Failure
+*/
 int spider_delete_tables(
   TABLE *table,
   const char *name,
@@ -1880,10 +1890,20 @@ int spider_delete_tables(
   {
     spider_store_tables_link_idx(table, roop_count);
     if ((error_num = spider_check_sys_table(table, table_key)))
-      break;
+    {
+      /* There's a problem with finding the first record for the
+      spider table, likely because it does not exist. Fail */
+      if (roop_count == 0)
+        DBUG_RETURN(error_num);
+      /* At least one row has been deleted for the Spider table.
+      Success */
+      else
+        break;
+    }
     else {
       if ((error_num = spider_delete_sys_table_row(table)))
       {
+        /* There's a problem deleting the row. Fail */
         DBUG_RETURN(error_num);
       }
     }