Too many waits on extension of relation - Mailing list pgsql-performance

Detail: Process holding the lock: 6423. Wait queue: 3718, 4600, 2670, 4046.
Context: SQL statement "INSERT INTO cms_c207c1e2_0ce7_422c_aafb_77d43f61e563.cms_item (display_name,ancestor_ids,content_size,case_node_id,case_model_id,case_instance_id,properties,mime_type,linked_ancestor_ids,linked_parent_folder_ids,payload_id,category,owner_id,version_no,latest,lock_time,lock_owner_id,version_label,chronicle_id,acl_id,trait_names,tags,parent_folder_id,updated_by,created_by,update_time,create_time,description,type,name,etag,id) VALUES (new.display_name,new.ancestor_ids,new.content_size,new.case_node_id,new.case_model_id,new.case_instance_id,json,new.mime_type,new.linked_ancestor_ids,new.linked_parent_folder_ids,new.payload_id,new.category,new.owner_id,new.version_no,new.latest,new.lock_time,new.lock_owner_id,new.version_label,new.chronicle_id,new.acl_id,new.trait_names,new.tags,new.parent_folder_id,new.updated_by,new.created_by,new.update_time,new.create_time,new.description,new.type,new.name,new.etag,new.id)"