Change Sysvar

Author: arjunsk

sql/sql_table.cc

@@ -10039,6 +10039,11 @@ bool mysql_create_table(THD *thd, Table_ref *create_table,
   Foreign_key_parents_invalidator fk_invalidator;
   DBUG_TRACE;
 
+  if (thd->variables.my_flag) {
+    my_error(ER_ILLEGAL_HA, MYF(0),"Fail on CREATE TABLE");
+    return true;
+  }
+
   handlerton *actual_hton = get_viable_handlerton_for_create(
       thd, create_table->table_name, *create_info);
   if (actual_hton == nullptr) return true;

sql/sys_vars.cc

@@ -3462,6 +3462,14 @@ static const char *optimizer_switch_names[] = {
     "derived_condition_pushdown",
     "default",
     NullS};
+
+
+static Sys_var_bool Sys_my_flag(
+  "my_flag",
+  "Custom flag to control CREATE TABLE behaviour",
+  HINT_UPDATEABLE SESSION_VAR(my_flag), CMD_LINE(OPT_ARG),
+  DEFAULT(false));
+
 static Sys_var_flagset Sys_optimizer_switch(
     "optimizer_switch",
     "optimizer_switch=option=val[,option=val...], where option is one of "

sql/system_variables.h

@@ -201,6 +201,7 @@ enum class Explain_format_type : ulong {
 */
 
 struct System_variables {
+  bool my_flag;
   /*
     How dynamically allocated system variables are handled: