SortKeyGenerator::SortKeyGenerator(OperationContext* txn,
const BSONObj& sortSpec,
const BSONObj& queryObj) {
_hasBounds = false;
_sortHasMeta = false;
_rawSortSpec = sortSpec;
// 'sortSpec' can be a mix of $meta and index key expressions. We pick it apart so that
// we only generate Btree keys for the index key expressions.
// The Btree key fields go in here. We pass this fake index key pattern to the Btree
// key generator below as part of generating sort keys for the docs.
BSONObjBuilder btreeBob;
BSONObjIterator it(sortSpec);
while (it.more()) {
BSONElement elt = it.next();
if (elt.isNumber()) {
// Btree key. elt (should be) foo: 1 or foo: -1.
btreeBob.append(elt);
} else if (LiteParsedQuery::isTextScoreMeta(elt)) {
_sortHasMeta = true;
} else {
// Sort spec. should have been validated before here.
verify(false);
}
}
// The fake index key pattern used to generate Btree keys.
_btreeObj = btreeBob.obj();
// If we're just sorting by meta, don't bother with all the key stuff.
if (_btreeObj.isEmpty()) {
return;
}
// We'll need to treat arrays as if we were to create an index over them. that is,
// we may need to unnest the first level and consider each array element to decide
// the sort order.
std::vector<const char*> fieldNames;
std::vector<BSONElement> fixed;
BSONObjIterator btreeIt(_btreeObj);
while (btreeIt.more()) {
BSONElement patternElt = btreeIt.next();
fieldNames.push_back(patternElt.fieldName());
fixed.push_back(BSONElement());
}
// TODO SERVER-23095: change nullptr to the appropriate CollationInterface*.
_keyGen.reset(new BtreeKeyGeneratorV1(fieldNames, fixed, false /* not sparse */, nullptr));
// The bounds checker only works on the Btree part of the sort key.
getBoundsForSort(txn, queryObj, _btreeObj);
if (_hasBounds) {
_boundsChecker.reset(new IndexBoundsChecker(&_bounds, _btreeObj, 1 /* == order */));
}
}
Status SortKeyGenerator::getSortKey(const WorkingSetMember& member, BSONObj* objOut) const {
BSONObj btreeKeyToUse;
Status btreeStatus = getBtreeKey(member.obj.value(), &btreeKeyToUse);
if (!btreeStatus.isOK()) {
return btreeStatus;
}
if (!_sortHasMeta) {
*objOut = btreeKeyToUse;
return Status::OK();
}
BSONObjBuilder mergedKeyBob;
// Merge metadata into the key.
BSONObjIterator it(_rawSortSpec);
BSONObjIterator btreeIt(btreeKeyToUse);
while (it.more()) {
BSONElement elt = it.next();
if (elt.isNumber()) {
// Merge btree key elt.
mergedKeyBob.append(btreeIt.next());
} else if (LiteParsedQuery::isTextScoreMeta(elt)) {
// Add text score metadata
double score = 0.0;
if (member.hasComputed(WSM_COMPUTED_TEXT_SCORE)) {
const TextScoreComputedData* scoreData = static_cast<const TextScoreComputedData*>(
member.getComputed(WSM_COMPUTED_TEXT_SCORE));
score = scoreData->getScore();
}
mergedKeyBob.append("$metaTextScore", score);
}
}
*objOut = mergedKeyBob.obj();
return Status::OK();
}