|virtual std::string||operator() (const Xapian::Document &doc) const|
|Build a key string for a Document. More...|
|Public Member Functions inherited from Xapian::KeyMaker|
|Virtual destructor, because we have virtual methods. More...|
KeyMaker subclass which combines several values.
When the result is used for sorting, results are ordered by the first value. In the event of a tie, the second is used. If this is the same for both, the third is used, and so on. If reverse is true for a value, then the sort order for that value is reversed.
When used for collapsing, the documents will only be considered equal if all the values specified match. If none of the specified values are set then the generated key will be empty, so such documents won't be collapsed (which is consistent with the behaviour in the "collapse on a value" case). If you'd prefer that documents with none of the keys set are collapsed together, then you can set reverse for at least one of the values. Other than this, it isn't useful to set reverse for collapsing.