Indexes Project::indexes()
{
Indexes idxs;
for (Indexes src = source->indexes(); ! nil(src); ++src)
if (subset(flds, *src))
idxs.push(*src);
return idxs;
}
Indexes Project::keys()
{
Indexes keys;
for (Indexes k = source->keys(); ! nil(k); ++k)
if (subset(flds, *k))
keys.push(*k);
return nil(keys) ? Indexes(flds) : keys;
}