Hopefully finally fixes MDEV-6282, MDEV-5748 and MDEV-6345

storage/oqgraph/graphcore-types.h

@@ -34,7 +34,9 @@ namespace open_query
 }
 
 
+// Forward defs from mariadb itself!
 class Field;
 typedef struct TABLE TABLE;
+class THD;
 
 #endif

storage/oqgraph/graphcore.cc

@@ -443,6 +443,9 @@ namespace open_query
     return num_vertices(share->g);
   }
 
+  THD* oqgraph::get_thd() { return share->g.get_table_thd(); }
+  void oqgraph::set_thd(THD* thd) { share->g.set_table_thd(thd); }
+
   oqgraph* oqgraph::create(oqgraph_share *share) throw()
   {
     assert(share != NULL);

storage/oqgraph/graphcore.h

@@ -126,6 +126,9 @@ namespace open_query
     static oqgraph* create(oqgraph_share*) throw();
     static oqgraph_share *create(TABLE*,Field*,Field*,Field*) throw();
 
+    THD* get_thd();
+    void set_thd(THD*);
+
     static void free(oqgraph*) throw();
     static void free(oqgraph_share*) throw();
 

storage/oqgraph/ha_oqgraph.cc

@@ -842,6 +842,11 @@ static int parse_latch_string_to_legacy_int(const String& value, int &latch)
 int ha_oqgraph::index_read_idx(byte * buf, uint index, const byte * key,
                         uint key_len, enum ha_rkey_function find_flag)
 {
+  if (graph->get_thd() != current_thd) {
+    DBUG_PRINT( "oq-debug", ("g->table->in_use: 0x%lx <-- current_thd 0x%lx", (long) graph->get_thd(), (long) current_thd));
+    graph->set_thd(current_thd);
+  }
+
   Field **field= table->field;
   KEY *key_info= table->key_info + index;
   int res;
@@ -1129,6 +1134,11 @@ int ha_oqgraph::rename_table(const char *, const char *)
 ha_rows ha_oqgraph::records_in_range(uint inx, key_range *min_key,
                                   key_range *max_key)
 {
+  if (graph->get_thd() != current_thd) {
+    DBUG_PRINT( "oq-debug", ("g->table->in_use: 0x%lx <-- current_thd 0x%lx", (long) graph->get_thd(), (long) current_thd));
+    graph->set_thd(current_thd);
+  }
+
   KEY *key=table->key_info+inx;
 #ifdef VERBOSE_DEBUG
   {

storage/oqgraph/oqgraph_thunk.cc

@@ -547,6 +547,9 @@ bool oqgraph3::cursor::operator!=(const cursor& x) const
   return record_position() != x._position;
 }
 
+::THD* oqgraph3::graph::get_table_thd() { return _table->in_use; }
+void oqgraph3::graph::set_table_thd(::THD* thd) { _table->in_use = thd; }
+
 oqgraph3::graph::graph(
     ::TABLE* table,
     ::Field* source,

storage/oqgraph/oqgraph_thunk.h

@@ -146,6 +146,9 @@ namespace oqgraph3
     ::Field* _target;
     ::Field* _weight;
 
+    ::THD* get_table_thd();
+    void set_table_thd(::THD* thd);
+
     graph(
         ::TABLE* table,
         ::Field* source,