Delete connected entities from collection quickly and consistently

[amivanoff]

• Too long DELETE query on the server in one-by-one deletion (1,5 seconds each) creates races with following SELECT
  • In did not took so long earlier, maybe inferencers are the cause
  • Maybe transactions could help with server-client state sync consistency
• Ability to delete connected entities
• Ability to delete references to the deleted entities

[amivanoff]

Consistent deletion of the one entity with references to it from other entities

DELETE {
  <iri> ?p01 ?o01.
  ?s02 ?p02 <iri>.
}
WHERE {
  {
    <iri> ?p01 ?o01.
  }
  UNION
  {
    ?s02 ?p02 <iri>
  }
}