algebra.py 文件源码

def translateAggregates(q, M):
    E = []
    A = []

    # collect/replace aggs in :
    #    select expr as ?var
    if q.projection:
        for v in q.projection:
            if v.evar: 
                v.expr = traverse(v.expr, functools.partial(_sample, v=v.evar))
                v.expr = traverse(v.expr, functools.partial(_aggs, A=A))


    # having clause
    if traverse(q.having, _hasAggregate, complete=False):
        q.having = traverse(q.having, _sample)
        traverse(q.having, functools.partial(_aggs, A=A))

    # order by
    if traverse(q.orderby, _hasAggregate, complete=False):
        q.orderby = traverse(q.orderby, _sample)
        traverse(q.orderby, functools.partial(_aggs, A=A))

    # sample all other select vars
    # TODO: only allowed for vars in group-by?
    if q.projection: 
        for v in q.projection: 
            if v.var:
                rv = Variable('__agg_%d__' % (len(A) + 1))
                A.append(CompValue('Aggregate_Sample', vars=v.var, res=rv))
                E.append((rv, v.var))

    return CompValue('AggregateJoin', A=A, p=M), E