MDEV-30265 Document some sts related functions in spider.

storage/spider/spd_db_mysql.cc

@@ -803,6 +803,7 @@ SPIDER_DB_ROW *spider_db_mbase_result::fetch_row_from_tmp_table(
   DBUG_RETURN((SPIDER_DB_ROW *) &row);
 }
 
+/* Fetches table status into `stat` */
 int spider_db_mbase_result::fetch_table_status(
   int mode,
   ha_statistics &stat
@@ -13393,6 +13394,9 @@ int spider_mbase_handler::sts_mode_exchange(
   DBUG_RETURN(sts_mode);
 }
 
+/**
+  Executes show table status query and stores results in share->stat.
+*/
 int spider_mbase_handler::show_table_status(
   int link_idx,
   int sts_mode,
@@ -13423,7 +13427,7 @@ int spider_mbase_handler::show_table_status(
       share);
     if (
       (error_num = spider_db_set_names(spider, conn, link_idx)) ||
-      (
+      ( /* Executes the `show table status` query */
         spider_db_query(
           conn,
           mysql_share->show_table_status[0 + pos].ptr(),
@@ -13536,6 +13540,7 @@ int spider_mbase_handler::show_table_status(
     conn->mta_conn_mutex_unlock_later = FALSE;
     SPIDER_CLEAR_FILE_POS(&conn->mta_conn_mutex_file_pos);
     pthread_mutex_unlock(&conn->mta_conn_mutex);
+    /* Fetches query results into share->stat. */
     error_num = res->fetch_table_status(
       sts_mode,
       share->stat

storage/spider/spd_sys_table.cc

@@ -979,6 +979,16 @@ void spider_store_xa_member_info(
   DBUG_VOID_RETURN;
 }
 
+/**
+  Store the DB and table names in a table.
+
+  If `name` starts with "./", separate out db and table names from
+  `name`. Otherwise store empty strings as names.
+
+  @param table        The table to store the info
+  @param name         The name of the table
+  @param name_length  The length of the name
+*/
 void spider_store_tables_name(
   TABLE *table,
   const char *name,
@@ -1443,6 +1453,12 @@ void spider_store_binlog_pos_gtid(
   DBUG_VOID_RETURN;
 }
 
+/**
+   Store sts info in the spider sts table.
+
+   Stores all fields except the db name and table name, which are
+   stored in `spider_store_tables_name()`.
+*/
 void spider_store_table_sts_info(
   TABLE *table,
   ha_statistics *stat
@@ -1595,6 +1611,18 @@ int spider_insert_sys_table(
   DBUG_RETURN(error_num);
 }
 
+/**
+  Inserts or updates a row in the spider sts system table
+
+  @param table       The spider sts system table
+  @param name        The name of the spider table whose stat will be
+                     inserted / updated in the sts table
+  @param name_length Length of the name
+  @param stat        The stat of the spider table that will be
+                     inserted / updated in the sts table
+
+  @retval 0 or error
+*/
 int spider_insert_or_update_table_sts(
   TABLE *table,
   const char *name,
@@ -2716,6 +2744,14 @@ int spider_get_sys_tables_static_link_id(
   DBUG_RETURN(error_num);
 }
 
+/**
+  Reads the table status from the system sts table
+
+  The result is set into `stat`
+
+  @param table  The system sts table
+  @param stat   The stat to read the table status into
+*/
 void spider_get_sys_table_sts_info(
   TABLE *table,
   ha_statistics *stat
@@ -3207,6 +3243,16 @@ int spider_get_link_statuses(
   DBUG_RETURN(0);
 }
 
+/**
+  Insert or update status of a table into the system sts table
+
+  @param thd          Connection
+  @param name         Name of the table whose status will be stored
+  @param name_length  Length of `name`
+  @param stat         The table status that will be stored into the
+                      system sts table
+  @param need_lock    Unused (fixme)
+*/
 int spider_sys_insert_or_update_table_sts(
   THD *thd,
   const char *name,
@@ -3345,6 +3391,15 @@ int spider_sys_delete_table_crd(
   DBUG_RETURN(error_num);
 }
 
+/**
+  Read table status of a table from the system sts table.
+
+  @param thd          Connection
+  @param name         The name of the table for which to read status of
+  @param name_length  The length `name`
+  @param stat         The struct to read the status into
+  @param need_lock    Unused (fixme)
+*/
 int spider_sys_get_table_sts(
   THD *thd,
   const char *name,

storage/spider/spd_table.cc

@@ -7138,8 +7138,11 @@ int spider_get_sts(
   if (need_to_get)
   {
     if (get_type == 0)
+      /* Copy table status from share to share->wide_share */
       spider_copy_sts_to_share(share, share->wide_share);
     else {
+      /* Executes a `show table status` query and store the results in
+      share->stat */
       error_num = spider_db_show_table_status(spider, link_idx, sts_mode, flag);
     }
   }