shared_ptr<PlanExecutor> PipelineD::addCursorSource(const intrusive_ptr<Pipeline>& pipeline,
const intrusive_ptr<ExpressionContext>& expCtx,
shared_ptr<PlanExecutor> exec,
DepsTracker deps,
const BSONObj& queryObj,
const BSONObj& sortObj,
const BSONObj& projectionObj) {
// Get the full "namespace" name.
const string& fullName = expCtx->ns.ns();
// Put the PlanExecutor into a DocumentSourceCursor and add it to the front of the pipeline.
intrusive_ptr<DocumentSourceCursor> pSource =
DocumentSourceCursor::create(fullName, exec, expCtx);
// Note the query, sort, and projection for explain.
pSource->setQuery(queryObj);
pSource->setSort(sortObj);
if (deps.hasNoRequirements()) {
pSource->shouldProduceEmptyDocs();
}
if (!projectionObj.isEmpty()) {
pSource->setProjection(projectionObj, boost::none);
} else {
// There may be fewer dependencies now if the sort was covered.
if (!sortObj.isEmpty()) {
deps = pipeline->getDependencies(queryObj);
}
pSource->setProjection(deps.toProjection(), deps.toParsedDeps());
}
// Add the initial DocumentSourceCursor to the front of the pipeline. Then optimize again in
// case the new stage can be absorbed with the first stages of the pipeline.
pipeline->addInitialSource(pSource);
pipeline->optimizePipeline();
// DocumentSourceCursor expects a yielding PlanExecutor that has had its state saved. We
// deregister the PlanExecutor so that it can be registered with ClientCursor.
exec->deregisterExec();
exec->saveState();
return exec;
}
boost::shared_ptr<Runner> PipelineD::prepareCursorSource(
Collection* collection,
const intrusive_ptr<Pipeline>& pPipeline,
const intrusive_ptr<ExpressionContext>& pExpCtx) {
// get the full "namespace" name
const string& fullName = pExpCtx->ns.ns();
pExpCtx->opCtx->lockState()->assertAtLeastReadLocked(fullName);
// We will be modifying the source vector as we go
Pipeline::SourceContainer& sources = pPipeline->sources;
// Inject a MongodImplementation to sources that need them.
for (size_t i = 0; i < sources.size(); i++) {
DocumentSourceNeedsMongod* needsMongod =
dynamic_cast<DocumentSourceNeedsMongod*>(sources[i].get());
if (needsMongod) {
needsMongod->injectMongodInterface(
boost::make_shared<MongodImplementation>(pExpCtx));
}
}
if (!sources.empty() && sources.front()->isValidInitialSource()) {
if (dynamic_cast<DocumentSourceMergeCursors*>(sources.front().get())) {
// Enable the hooks for setting up authentication on the subsequent internal
// connections we are going to create. This would normally have been done
// when SetShardVersion was called, but since SetShardVersion is never called
// on secondaries, this is needed.
ShardedConnectionInfo::addHook();
}
return boost::shared_ptr<Runner>(); // don't need a cursor
}
// Look for an initial match. This works whether we got an initial query or not.
// If not, it results in a "{}" query, which will be what we want in that case.
const BSONObj queryObj = pPipeline->getInitialQuery();
if (!queryObj.isEmpty()) {
// This will get built in to the Cursor we'll create, so
// remove the match from the pipeline
sources.pop_front();
}
// Find the set of fields in the source documents depended on by this pipeline.
const DepsTracker deps = pPipeline->getDependencies(queryObj);
// Passing query an empty projection since it is faster to use ParsedDeps::extractFields().
// This will need to change to support covering indexes (SERVER-12015). There is an
// exception for textScore since that can only be retrieved by a query projection.
const BSONObj projectionForQuery = deps.needTextScore ? deps.toProjection() : BSONObj();
/*
Look for an initial sort; we'll try to add this to the
Cursor we create. If we're successful in doing that (further down),
we'll remove the $sort from the pipeline, because the documents
will already come sorted in the specified order as a result of the
index scan.
*/
intrusive_ptr<DocumentSourceSort> sortStage;
BSONObj sortObj;
if (!sources.empty()) {
sortStage = dynamic_cast<DocumentSourceSort*>(sources.front().get());
if (sortStage) {
// build the sort key
sortObj = sortStage->serializeSortKey(/*explain*/false).toBson();
}
}
// Create the Runner.
//
// If we try to create a Runner that includes both the match and the
// sort, and the two are incompatible wrt the available indexes, then
// we don't get a Runner back.
//
// So we try to use both first. If that fails, try again, without the
// sort.
//
// If we don't have a sort, jump straight to just creating a Runner
// without the sort.
//
// If we are able to incorporate the sort into the Runner, remove it
// from the head of the pipeline.
//
// LATER - we should be able to find this out before we create the
// cursor. Either way, we can then apply other optimizations there
// are tickets for, such as SERVER-4507.
const size_t runnerOptions = QueryPlannerParams::DEFAULT
| QueryPlannerParams::INCLUDE_SHARD_FILTER
| QueryPlannerParams::NO_BLOCKING_SORT
;
boost::shared_ptr<Runner> runner;
bool sortInRunner = false;
const WhereCallbackReal whereCallback(pExpCtx->ns.db());
if (sortStage) {
CanonicalQuery* cq;
Status status =
CanonicalQuery::canonicalize(pExpCtx->ns,
queryObj,
sortObj,
projectionForQuery,
&cq,
whereCallback);
Runner* rawRunner;
if (status.isOK() && getRunner(collection, cq, &rawRunner, runnerOptions).isOK()) {
// success: The Runner will handle sorting for us using an index.
runner.reset(rawRunner);
sortInRunner = true;
sources.pop_front();
if (sortStage->getLimitSrc()) {
// need to reinsert coalesced $limit after removing $sort
sources.push_front(sortStage->getLimitSrc());
}
}
}
if (!runner.get()) {
const BSONObj noSort;
CanonicalQuery* cq;
uassertStatusOK(
CanonicalQuery::canonicalize(pExpCtx->ns,
queryObj,
noSort,
projectionForQuery,
&cq,
whereCallback));
Runner* rawRunner;
uassertStatusOK(getRunner(collection, cq, &rawRunner, runnerOptions));
runner.reset(rawRunner);
}
// DocumentSourceCursor expects a yielding Runner that has had its state saved.
runner->saveState();
// Put the Runner into a DocumentSourceCursor and add it to the front of the pipeline.
intrusive_ptr<DocumentSourceCursor> pSource =
DocumentSourceCursor::create(fullName, runner, pExpCtx);
// Note the query, sort, and projection for explain.
pSource->setQuery(queryObj);
if (sortInRunner)
pSource->setSort(sortObj);
pSource->setProjection(deps.toProjection(), deps.toParsedDeps());
while (!sources.empty() && pSource->coalesce(sources.front())) {
sources.pop_front();
}
pPipeline->addInitialSource(pSource);
return runner;
}