want to remove entity that has no label from the result - sparql

Question

I'd like to ask one tricky thing about label. Using SERVICE keyword like SERVICE wikibase:label { bd:serviceParam wikibase:language "ko,en". } enable us to switch language label when the first preference is not mached to the target entity label.
However, I want to drop out some entities that does not have any label. However, the service keyword add entity with Qxxxx label when the entity does not have any language match label. How could I remove the entity from the result?
I know we can filter that out using rdfs:label for the all the variables explicitly but setting all the rdfs:label to all the variables is another headeache. So I'd like to know how to improve the query with SERVICE wikibase:label I want to filter out entity that doesn't have any label. Should I replace SERVICE with rdfs:label?
SELECT DISTINCT ?vLabel
WHERE {
hint:Query hint:optimizer "None" .
{
SELECT DISTINCT ?i {
?i wdt:P31 wd:Q515.
}LIMIT 15
}
?v wdt:P937 ?i.
SERVICE wikibase:label { bd:serviceParam wikibase:language "ko,en". }
}
LIMIT 3
RESULT:
Q59780594 <- no lang label
Q24642253 <- no lang label

Answer 1

The Wikidata label service doesn't provide a built-in way to skip resources that don't have a label.
The simplest option would be to wrap the query as a subquery into a new SELECT query, and use a filter to remove any Qxxxx labels. This uses the fact that only the real labels have a language tag:
SELECT ?vLabel {
{
SELECT DISTINCT ?vLabel
...
}
FILTER lang(?vLabel)
}
Edit: Below is my original (and inferior) answer, which used a regular expression on the label itself to remove the Qxxxx ones. It would also filter out any resources that actually have a label of the form Qxxxx, if such resources exist in Wikidata.
SELECT ?vLabel {
{
SELECT DISTINCT ?vLabel
...
}
FILTER (!REGEX(?vLabel, "^Q[0-9]+$"))
}