MDEV-10957: Assertion failure when dropping a myisam table

... with wsrep_replicate_myisam enabled

Internal updates to system statistical tables could wrongly
trigger an additional total-order replication if wsrep_repli
-cate_myisam is enabled.
Fixed by adding a check to skip total-order replication for
stat tables.

sql/sql_base.cc

@@ -4068,6 +4068,7 @@ bool open_tables(THD *thd, const DDL_options_st &options,
       (*start)                                 &&
       (*start)->table                          &&
       (*start)->table->file->ht == myisam_hton &&
+      !is_stat_table((*start)->db, (*start)->alias) &&
       sqlcom_can_generate_row_events(thd)      &&
       thd->get_command() != COM_STMT_PREPARE)
   {

sql/sql_statistics.cc

@@ -3849,3 +3849,21 @@ double Histogram::point_selectivity(double pos, double avg_sel)
   return sel;
 }
 
+/*
+  Check whether the table is one of the persistent statistical tables.
+*/
+bool is_stat_table(const char *db, const char *table)
+{
+  DBUG_ASSERT(db && table);
+
+  if (!memcmp(db, stat_tables_db_name.str, stat_tables_db_name.length))
+  {
+    for (uint i= 0; i < STATISTICS_TABLES; i ++)
+    {
+      if (!memcmp(table, stat_table_name[i].str, stat_table_name[i].length))
+        return true;
+    }
+  }
+  return false;
+}
+

sql/sql_statistics.h

@@ -107,6 +107,7 @@ double get_column_range_cardinality(Field *field,
                                     key_range *min_endp,
                                     key_range *max_endp,
                                     uint range_flag);
+bool is_stat_table(const char *db, const char *table);
 
 class Histogram
 {