[source/native] refactor eid generation code
This set of related methods clutters the native source API.
It will be better served with a dedicated eid genrator object.
Related to #3526594.
[jcr: allocate the eid generator in __init__]
for eschema in schema.entities():
if not (eschema.final or 'cw_source' in eschema.subjrels):
add_relation_definition(eschema.type, 'cw_source', 'CWSource', ask_confirm=False)
sql('INSERT INTO cw_source_relation(eid_from, eid_to) '
'SELECT e.eid,s.cw_eid FROM entities as e, cw_CWSource as s '
'WHERE s.cw_name=e.source AND NOT EXISTS(SELECT 1 FROM cw_source_relation WHERE eid_from=e.eid AND eid_to=s.cw_eid)')
commit()