DocumentSourceChangeStreamTransform::DocumentSourceChangeStreamTransform(
const boost::intrusive_ptr<ExpressionContext>& expCtx,
const ServerGlobalParams::FeatureCompatibility::Version& fcv,
BSONObj changeStreamSpec)
: DocumentSource(expCtx),
_changeStreamSpec(changeStreamSpec.getOwned()),
_isIndependentOfAnyCollection(expCtx->ns.isCollectionlessAggregateNS()),
_fcv(fcv) {
_nsRegex.emplace(DocumentSourceChangeStream::getNsRegexForChangeStream(expCtx->ns));
auto spec = DocumentSourceChangeStreamSpec::parse(IDLParserErrorContext("$changeStream"),
_changeStreamSpec);
// If the change stream spec includes a resumeToken with a shard key, populate the document key
// cache with the field paths.
auto resumeAfter = spec.getResumeAfter();
auto startAfter = spec.getStartAfter();
if (resumeAfter || startAfter) {
ResumeToken token = resumeAfter ? resumeAfter.get() : startAfter.get();
ResumeTokenData tokenData = token.getData();
if (!tokenData.documentKey.missing() && tokenData.uuid) {
std::vector<FieldPath> docKeyFields;
auto docKey = tokenData.documentKey.getDocument();
auto iter = docKey.fieldIterator();
while (iter.more()) {
auto fieldPair = iter.next();
docKeyFields.push_back(fieldPair.first);
}
// If the document key from the resume token has more than one field, that means it
// includes the shard key and thus should never change.
auto isFinal = docKey.size() > 1;
_documentKeyCache[tokenData.uuid.get()] =
DocumentKeyCacheEntry({docKeyFields, isFinal});
}
}
}
