MDEV-33191 spider: fix dbton_id when iterating over links

There are two array fields in spider_share with similar names:

share->use_sql_dbton_ids that maps from i to the i-th dbton used by
share. Thus it should be used only when i iterates over all distinct
dbtons used by share.

share->sql_dbton_ids that maps from i to the dbton used by the i-th
link of the share. Thus it should be used only when i iterates over
all links of a share.

We correct instances where share->sql_dbton_ids should be used instead
of share->use_sql_dbton_ids.

storage/spider/ha_spider.cc

@@ -8392,7 +8392,7 @@ int ha_spider::ft_read_internal(
         }
       } else {
 #endif
-        uint dbton_id = share->use_sql_dbton_ids[roop_count];
+        uint dbton_id = share->sql_dbton_ids[roop_count];
         spider_db_handler *dbton_hdl = dbton_handler[dbton_id];
         SPIDER_CONN *conn = conns[roop_count];
         pthread_mutex_assert_not_owner(&conn->mta_conn_mutex);
@@ -13135,7 +13135,7 @@ int ha_spider::drop_tmp_tables()
     ) {
       if (spider_bit_is_set(result_list.tmp_table_created, roop_count))
       {
-        uint dbton_id = share->use_sql_dbton_ids[roop_count];
+        uint dbton_id = share->sql_dbton_ids[roop_count];
         spider_db_handler *dbton_hdl = dbton_handler[dbton_id];
         SPIDER_CONN *conn = conns[roop_count];
         pthread_mutex_assert_not_owner(&conn->mta_conn_mutex);

storage/spider/mysql-test/spider/bugfix/r/mdev_33191.result

+INSTALL SONAME 'ha_spider';
+set spider_same_server_link=on;
+CREATE TABLE t2(c INT);
+CREATE TABLE t1(c INT) ENGINE=Spider COMMENT='socket "$SOCKET", user "root", table "t2 t3"';
+ALTER TABLE t1 ENGINE=Spider;
+TRUNCATE TABLE t1;
+ERROR 42S02: Table 'test.t3' doesn't exist
+drop table t1, t2;
+Warnings:
+Warning	1620	Plugin is busy and will be uninstalled on shutdown

storage/spider/mysql-test/spider/bugfix/t/mdev_33191.test

+INSTALL SONAME 'ha_spider';
+set spider_same_server_link=on;
+CREATE TABLE t2(c INT);
+--let $SOCKET=`SELECT @@global.socket`
+evalp CREATE TABLE t1(c INT) ENGINE=Spider COMMENT='socket "$SOCKET", user "root", table "t2 t3"';
+ALTER TABLE t1 ENGINE=Spider;
+--error ER_NO_SUCH_TABLE
+TRUNCATE TABLE t1;
+drop table t1, t2;
+--disable_query_log
+--source ../../include/clean_up_spider.inc

storage/spider/spd_db_conn.cc

@@ -8215,7 +8215,7 @@ int spider_db_delete_all_rows(
       spider->conn_link_idx, roop_count, share->link_count,
       SPIDER_LINK_STATUS_RECOVERY)
   ) {
-    uint dbton_id = share->use_sql_dbton_ids[roop_count];
+    uint dbton_id = share->sql_dbton_ids[roop_count];
     spider_db_handler *dbton_hdl = spider->dbton_handler[dbton_id];
     conn = spider->conns[roop_count];
     pthread_mutex_assert_not_owner(&conn->mta_conn_mutex);

storage/spider/spd_db_include.h

@@ -1836,6 +1836,12 @@ enum spider_db_access_type
   SPIDER_DB_ACCESS_TYPE_NOSQL
 };
 
+/*
+  Type of singletons based on the type of the remote database.
+
+  All such singletons are stored in the array `spider_dbton', see
+  `spider_db_init()'.
+*/
 typedef struct st_spider_dbton
 {
   uint dbton_id;

storage/spider/spd_include.h

@@ -1358,6 +1358,7 @@ typedef struct st_spider_share
   uint               *hs_read_conn_keys_lengths;
   uint               *hs_write_conn_keys_lengths;
 #endif
+  /* The index in `spider_dbton' of each data node link. */
   uint               *sql_dbton_ids;
 #if defined(HS_HAS_SQLCOM) && defined(HAVE_HANDLERSOCKET)
   uint               *hs_dbton_ids;
@@ -1447,14 +1448,23 @@ typedef struct st_spider_share
   uchar              dbton_bitmap[spider_bitmap_size(SPIDER_DBTON_SIZE)];
   spider_db_share    *dbton_share[SPIDER_DBTON_SIZE];
   uint               use_dbton_count;
+  /* Actual size is `use_dbton_count'. Values are the indices of item
+  in `spider_dbton'. */
   uint               use_dbton_ids[SPIDER_DBTON_SIZE];
+  /* Inverse map of `use_dbton_ids'. */
   uint               dbton_id_to_seq[SPIDER_DBTON_SIZE];
   uint               use_sql_dbton_count;
+  /* Actual size is `use_sql_dbton_count'. Values are the indices of
+  item in `spider_dbton'. */
   uint               use_sql_dbton_ids[SPIDER_DBTON_SIZE];
+  /* Inverse map of `use_sql_dbton_ids'. */
   uint               sql_dbton_id_to_seq[SPIDER_DBTON_SIZE];
 #if defined(HS_HAS_SQLCOM) && defined(HAVE_HANDLERSOCKET)
   uint               use_hs_dbton_count;
+  /* Actual size is `use_hs_dbton_count'. Values are the indices of
+  item in `spider_dbton'. */
   uint               use_hs_dbton_ids[SPIDER_DBTON_SIZE];
+  /* Inverse map of `use_hs_dbton_ids'. */
   uint               hs_dbton_id_to_seq[SPIDER_DBTON_SIZE];
 #endif