I have a relation select field of a node, which allows to add multiple references to other nodes. The maximum arrity for the relation is infinate, but lower does not help. When the number of nodes added in the selection is greater than 4, I get the following error after saving the node times out:

PDOException: SQLSTATE[HY000]: General error: 1205 Lock wait timeout exceeded; try restarting transaction: UPDATE {node} SET vid=:db_update_placeholder_0, type=:db_update_placeholder_1, language=:db_update_placeholder_2, title=:db_update_placeholder_3, uid=:db_update_placeholder_4, status=:db_update_placeholder_5, created=:db_update_placeholder_6, changed=:db_update_placeholder_7, comment=:db_update_placeholder_8, promote=:db_update_placeholder_9, sticky=:db_update_placeholder_10, tnid=:db_update_placeholder_11, translate=:db_update_placeholder_12 WHERE (nid = :db_condition_placeholder_0) ; Array ( [:db_update_placeholder_0] => 128 [:db_update_placeholder_1] => publication [:db_update_placeholder_2] => und [:db_update_placeholder_3] => Top-gated graphene nanoribbon transistors with ultrathin high-k dielectrics [:db_update_placeholder_4] => 1 [:db_update_placeholder_5] => 1 [:db_update_placeholder_6] => 1360557522 [:db_update_placeholder_7] => 1360562148 [:db_update_placeholder_8] => 0 [:db_update_placeholder_9] => 1 [:db_update_placeholder_10] => 0 [:db_update_placeholder_11] => 0 [:db_update_placeholder_12] => 0 [:db_condition_placeholder_0] => 128 ) in drupal_write_record() (line 7106 of /home/drupalpro/websites/example7.dev/includes/common.inc).