private String decodeSummary(String summaryClass, FastHit hit, byte[] docsumdata) {
        // System.err.println("get db from q");
        DocumentDatabase db = getDocumentDatabase(hit.getQuery());
        hit.setField(Hit.SDDOCNAME_FIELD, db.schema().name());
        return decodeSummary(summaryClass, hit, docsumdata, db.getDocsumDefinitionSet());
    }
Fills the hits.

@return the number of hits that we did not return data for, and an optional error message.
        when things are working normally we return 0.
container-search/src/main/java/com/yahoo/vespa/streamingvisitors/StreamingBackend.java