MDEV-35042 Vector indexes are allowed for MERGE tables, but do not

disallow hlindexes in MERGE - because we cannot create the secondary
table *in the same engine*

mysql-test/main/vector2.result

@@ -51,3 +51,10 @@ create table t (a int primary key, v blob not null, vector index(v));
 alter table t modify a int auto_increment, lock=none;
 ERROR 0A000: LOCK=NONE is not supported. Reason: CHANGE COLUMN ... AUTO_INCREMENT. Try LOCK=SHARED
 drop table t;
+#
+# MDEV-35042 Vector indexes are allowed for MERGE tables, but do not
+#
+create table t (a int, v blob not null, vector index(v)) engine=myisam;
+create table tm (a int, v blob not null, vector index(v)) engine=merge union=(t);
+ERROR HY000: Table storage engine 'MERGE' does not support the create option 'VECTOR'
+drop table t;

mysql-test/main/vector2.test

@@ -56,3 +56,10 @@ create table t (a int primary key, v blob not null, vector index(v));
 alter table t modify a int auto_increment, lock=none;
 drop table t;
 
+--echo #
+--echo # MDEV-35042 Vector indexes are allowed for MERGE tables, but do not
+--echo #
+create table t (a int, v blob not null, vector index(v)) engine=myisam;
+--error ER_ILLEGAL_HA_CREATE_OPTION
+create table tm (a int, v blob not null, vector index(v)) engine=merge union=(t);
+drop table t;

storage/myisammrg/ha_myisammrg.cc

@@ -1555,6 +1555,11 @@ int ha_myisammrg::create(const char *name, TABLE *form,
 {
   char buff[FN_REFLEN];
   DBUG_ENTER("ha_myisammrg::create");
+  if (form->s->total_keys > form->s->keys)
+  {
+    my_error(ER_ILLEGAL_HA_CREATE_OPTION, MYF(0), "MERGE", "VECTOR");
+    DBUG_RETURN(HA_ERR_UNSUPPORTED);
+  }
   fn_format(buff, name, "", MYRG_NAME_EXT, MY_UNPACK_FILENAME | MY_APPEND_EXT);
   int res= create_mrg(buff, create_info);
   DBUG_RETURN(res);