[CWEP002] introduce RQLRelationRewriter
Refactor existing RQLRewriter for later reuse of rewriting relation as specified
by CWEP002. Work is different because we simply want to replace a relation by
another rql snippet and we don't have to bother with EXISTS, subqueries and all.
This rewriter is not yet plugged into the querier.
Depends on yams 0.40 API.
Related to #3546717
try:
rtype, = __args__
except ValueError:
print 'USAGE: cubicweb-ctl shell <instance> detect_cycle.py -- <relation type>'
print
graph = {}
for fromeid, toeid in rql('Any X,Y WHERE X %s Y' % rtype):
graph.setdefault(fromeid, []).append(toeid)
from logilab.common.graph import get_cycles
for cycle in get_cycles(graph):
print 'cycle', '->'.join(str(n) for n in cycle)