Status explain(OperationContext* txn,
const std::string& dbname,
const BSONObj& cmdObj,
ExplainCommon::Verbosity verbosity,
const rpc::ServerSelectionMetadata&,
BSONObjBuilder* out) const override {
const std::string fullns = parseNs(dbname, cmdObj);
const NamespaceString nss(fullns);
if (!nss.isValid()) {
return {ErrorCodes::InvalidNamespace,
str::stream() << "Invalid collection name: " << nss.ns()};
}
// Parse the command BSON to a LiteParsedQuery.
const bool isExplain = true;
auto lpqStatus = LiteParsedQuery::makeFromFindCommand(nss, cmdObj, isExplain);
if (!lpqStatus.isOK()) {
return lpqStatus.getStatus();
}
// Finish the parsing step by using the LiteParsedQuery to create a CanonicalQuery.
ExtensionsCallbackReal extensionsCallback(txn, &nss);
auto statusWithCQ =
CanonicalQuery::canonicalize(lpqStatus.getValue().release(), extensionsCallback);
if (!statusWithCQ.isOK()) {
return statusWithCQ.getStatus();
}
std::unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
AutoGetCollectionForRead ctx(txn, nss);
// The collection may be NULL. If so, getExecutor() should handle it by returning
// an execution tree with an EOFStage.
Collection* collection = ctx.getCollection();
// We have a parsed query. Time to get the execution plan for it.
auto statusWithPlanExecutor =
getExecutorFind(txn, collection, nss, std::move(cq), PlanExecutor::YIELD_AUTO);
if (!statusWithPlanExecutor.isOK()) {
return statusWithPlanExecutor.getStatus();
}
std::unique_ptr<PlanExecutor> exec = std::move(statusWithPlanExecutor.getValue());
// Got the execution tree. Explain it.
Explain::explainStages(exec.get(), verbosity, out);
return Status::OK();
}
/**
* Runs a query using the following steps:
* --Parsing.
* --Acquire locks.
* --Plan query, obtaining an executor that can run it.
* --Generate the first batch.
* --Save state for getMore, transferring ownership of the executor to a ClientCursor.
* --Generate response to send to the client.
*/
bool run(OperationContext* txn,
const std::string& dbname,
BSONObj& cmdObj,
int options,
std::string& errmsg,
BSONObjBuilder& result) override {
const std::string fullns = parseNs(dbname, cmdObj);
const NamespaceString nss(fullns);
if (!nss.isValid() || nss.isCommand() || nss.isSpecialCommand()) {
return appendCommandStatus(result,
{ErrorCodes::InvalidNamespace,
str::stream() << "Invalid collection name: " << nss.ns()});
}
// Although it is a command, a find command gets counted as a query.
globalOpCounters.gotQuery();
if (txn->getClient()->isInDirectClient()) {
return appendCommandStatus(
result,
Status(ErrorCodes::IllegalOperation, "Cannot run find command from eval()"));
}
// Parse the command BSON to a LiteParsedQuery.
const bool isExplain = false;
auto lpqStatus = LiteParsedQuery::makeFromFindCommand(nss, cmdObj, isExplain);
if (!lpqStatus.isOK()) {
return appendCommandStatus(result, lpqStatus.getStatus());
}
auto& lpq = lpqStatus.getValue();
// Validate term before acquiring locks, if provided.
if (auto term = lpq->getReplicationTerm()) {
auto replCoord = repl::ReplicationCoordinator::get(txn);
Status status = replCoord->updateTerm(txn, *term);
// Note: updateTerm returns ok if term stayed the same.
if (!status.isOK()) {
return appendCommandStatus(result, status);
}
}
// Fill out curop information.
//
// We pass negative values for 'ntoreturn' and 'ntoskip' to indicate that these values
// should be omitted from the log line. Limit and skip information is already present in the
// find command parameters, so these fields are redundant.
const int ntoreturn = -1;
const int ntoskip = -1;
beginQueryOp(txn, nss, cmdObj, ntoreturn, ntoskip);
// Finish the parsing step by using the LiteParsedQuery to create a CanonicalQuery.
ExtensionsCallbackReal extensionsCallback(txn, &nss);
auto statusWithCQ = CanonicalQuery::canonicalize(lpq.release(), extensionsCallback);
if (!statusWithCQ.isOK()) {
return appendCommandStatus(result, statusWithCQ.getStatus());
}
std::unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
ShardingState* const shardingState = ShardingState::get(txn);
if (OperationShardVersion::get(txn).hasShardVersion() && shardingState->enabled()) {
ChunkVersion receivedVersion = OperationShardVersion::get(txn).getShardVersion(nss);
ChunkVersion latestVersion;
// Wait for migration completion to get the correct chunk version.
const int maxTimeoutSec = 30;
int timeoutSec = cq->getParsed().getMaxTimeMS() / 1000;
if (!timeoutSec || timeoutSec > maxTimeoutSec) {
timeoutSec = maxTimeoutSec;
}
if (!shardingState->waitTillNotInCriticalSection(timeoutSec)) {
uasserted(ErrorCodes::LockTimeout, "Timeout while waiting for migration commit");
}
// If the received version is newer than the version cached in 'shardingState', then we
// have to refresh 'shardingState' from the config servers. We do this before acquiring
// locks so that we don't hold locks while waiting on the network.
uassertStatusOK(shardingState->refreshMetadataIfNeeded(
txn, nss.ns(), receivedVersion, &latestVersion));
}
// Acquire locks.
AutoGetCollectionForRead ctx(txn, nss);
Collection* collection = ctx.getCollection();
const int dbProfilingLevel =
ctx.getDb() ? ctx.getDb()->getProfilingLevel() : serverGlobalParams.defaultProfile;
// It is possible that the sharding version will change during yield while we are
// retrieving a plan executor. If this happens we will throw an error and mongos will
// retry.
const ChunkVersion shardingVersionAtStart = shardingState->getVersion(nss.ns());
// Get the execution plan for the query.
auto statusWithPlanExecutor =
getExecutorFind(txn, collection, nss, std::move(cq), PlanExecutor::YIELD_AUTO);
if (!statusWithPlanExecutor.isOK()) {
return appendCommandStatus(result, statusWithPlanExecutor.getStatus());
}
std::unique_ptr<PlanExecutor> exec = std::move(statusWithPlanExecutor.getValue());
if (!collection) {
// No collection. Just fill out curop indicating that there were zero results and
// there is no ClientCursor id, and then return.
const long long numResults = 0;
const CursorId cursorId = 0;
endQueryOp(txn, collection, *exec, dbProfilingLevel, numResults, cursorId);
appendCursorResponseObject(cursorId, nss.ns(), BSONArray(), &result);
return true;
}
const LiteParsedQuery& pq = exec->getCanonicalQuery()->getParsed();
// Stream query results, adding them to a BSONArray as we go.
BSONArrayBuilder firstBatch;
BSONObj obj;
PlanExecutor::ExecState state = PlanExecutor::ADVANCED;
long long numResults = 0;
while (!FindCommon::enoughForFirstBatch(pq, numResults, firstBatch.len()) &&
PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
// If adding this object will cause us to exceed the BSON size limit, then we stash
// it for later.
if (firstBatch.len() + obj.objsize() > BSONObjMaxUserSize && numResults > 0) {
exec->enqueue(obj);
break;
}
// Add result to output buffer.
firstBatch.append(obj);
numResults++;
}
// Throw an assertion if query execution fails for any reason.
if (PlanExecutor::FAILURE == state || PlanExecutor::DEAD == state) {
const std::unique_ptr<PlanStageStats> stats(exec->getStats());
error() << "Plan executor error during find command: " << PlanExecutor::statestr(state)
<< ", stats: " << Explain::statsToBSON(*stats);
return appendCommandStatus(result,
Status(ErrorCodes::OperationFailed,
str::stream()
<< "Executor error during find command: "
<< WorkingSetCommon::toStatusString(obj)));
}
// TODO: Currently, chunk ranges are kept around until all ClientCursors created while the
// chunk belonged on this node are gone. Separating chunk lifetime management from
// ClientCursor should allow this check to go away.
if (!shardingState->getVersion(nss.ns()).isWriteCompatibleWith(shardingVersionAtStart)) {
// Version changed while retrieving a PlanExecutor. Terminate the operation,
// signaling that mongos should retry.
throw SendStaleConfigException(nss.ns(),
"version changed during find command",
shardingVersionAtStart,
shardingState->getVersion(nss.ns()));
}
// Set up the cursor for getMore.
CursorId cursorId = 0;
if (shouldSaveCursor(txn, collection, state, exec.get())) {
// Register the execution plan inside a ClientCursor. Ownership of the PlanExecutor is
// transferred to the ClientCursor.
//
// First unregister the PlanExecutor so it can be re-registered with ClientCursor.
exec->deregisterExec();
// Create a ClientCursor containing this plan executor. We don't have to worry about
// leaking it as it's inserted into a global map by its ctor.
ClientCursor* cursor =
new ClientCursor(collection->getCursorManager(),
exec.release(),
nss.ns(),
txn->recoveryUnit()->isReadingFromMajorityCommittedSnapshot(),
pq.getOptions(),
pq.getFilter());
cursorId = cursor->cursorid();
invariant(!exec);
PlanExecutor* cursorExec = cursor->getExecutor();
// State will be restored on getMore.
cursorExec->saveState();
cursorExec->detachFromOperationContext();
cursor->setLeftoverMaxTimeMicros(CurOp::get(txn)->getRemainingMaxTimeMicros());
cursor->setPos(numResults);
// Fill out curop based on the results.
endQueryOp(txn, collection, *cursorExec, dbProfilingLevel, numResults, cursorId);
} else {
endQueryOp(txn, collection, *exec, dbProfilingLevel, numResults, cursorId);
}
// Generate the response object to send to the client.
appendCursorResponseObject(cursorId, nss.ns(), firstBatch.arr(), &result);
return true;
}
/**
* Runs a query using the following steps:
* --Parsing.
* --Acquire locks.
* --Plan query, obtaining an executor that can run it.
* --Generate the first batch.
* --Save state for getMore, transferring ownership of the executor to a ClientCursor.
* --Generate response to send to the client.
*/
bool run(OperationContext* txn,
const std::string& dbname,
BSONObj& cmdObj,
int options,
std::string& errmsg,
BSONObjBuilder& result) override {
const NamespaceString nss(parseNs(dbname, cmdObj));
if (!nss.isValid() || nss.isCommand() || nss.isSpecialCommand()) {
return appendCommandStatus(result,
{ErrorCodes::InvalidNamespace,
str::stream() << "Invalid collection name: " << nss.ns()});
}
// Although it is a command, a find command gets counted as a query.
globalOpCounters.gotQuery();
if (txn->getClient()->isInDirectClient()) {
return appendCommandStatus(
result,
Status(ErrorCodes::IllegalOperation, "Cannot run find command from eval()"));
}
// Parse the command BSON to a QueryRequest.
const bool isExplain = false;
auto qrStatus = QueryRequest::makeFromFindCommand(nss, cmdObj, isExplain);
if (!qrStatus.isOK()) {
return appendCommandStatus(result, qrStatus.getStatus());
}
auto& qr = qrStatus.getValue();
// Validate term before acquiring locks, if provided.
if (auto term = qr->getReplicationTerm()) {
auto replCoord = repl::ReplicationCoordinator::get(txn);
Status status = replCoord->updateTerm(txn, *term);
// Note: updateTerm returns ok if term stayed the same.
if (!status.isOK()) {
return appendCommandStatus(result, status);
}
}
// Fill out curop information.
//
// We pass negative values for 'ntoreturn' and 'ntoskip' to indicate that these values
// should be omitted from the log line. Limit and skip information is already present in the
// find command parameters, so these fields are redundant.
const int ntoreturn = -1;
const int ntoskip = -1;
beginQueryOp(txn, nss, cmdObj, ntoreturn, ntoskip);
// Finish the parsing step by using the QueryRequest to create a CanonicalQuery.
ExtensionsCallbackReal extensionsCallback(txn, &nss);
auto statusWithCQ = CanonicalQuery::canonicalize(txn, std::move(qr), extensionsCallback);
if (!statusWithCQ.isOK()) {
return appendCommandStatus(result, statusWithCQ.getStatus());
}
std::unique_ptr<CanonicalQuery> cq = std::move(statusWithCQ.getValue());
// Acquire locks.
AutoGetCollectionForRead ctx(txn, nss);
Collection* collection = ctx.getCollection();
// Get the execution plan for the query.
auto statusWithPlanExecutor =
getExecutorFind(txn, collection, nss, std::move(cq), PlanExecutor::YIELD_AUTO);
if (!statusWithPlanExecutor.isOK()) {
return appendCommandStatus(result, statusWithPlanExecutor.getStatus());
}
std::unique_ptr<PlanExecutor> exec = std::move(statusWithPlanExecutor.getValue());
{
stdx::lock_guard<Client>(*txn->getClient());
CurOp::get(txn)->setPlanSummary_inlock(Explain::getPlanSummary(exec.get()));
}
if (!collection) {
// No collection. Just fill out curop indicating that there were zero results and
// there is no ClientCursor id, and then return.
const long long numResults = 0;
const CursorId cursorId = 0;
endQueryOp(txn, collection, *exec, numResults, cursorId);
appendCursorResponseObject(cursorId, nss.ns(), BSONArray(), &result);
return true;
}
const QueryRequest& originalQR = exec->getCanonicalQuery()->getQueryRequest();
// Stream query results, adding them to a BSONArray as we go.
CursorResponseBuilder firstBatch(/*isInitialResponse*/ true, &result);
BSONObj obj;
PlanExecutor::ExecState state = PlanExecutor::ADVANCED;
long long numResults = 0;
while (!FindCommon::enoughForFirstBatch(originalQR, numResults) &&
PlanExecutor::ADVANCED == (state = exec->getNext(&obj, NULL))) {
// If we can't fit this result inside the current batch, then we stash it for later.
if (!FindCommon::haveSpaceForNext(obj, numResults, firstBatch.bytesUsed())) {
exec->enqueue(obj);
break;
}
// Add result to output buffer.
firstBatch.append(obj);
numResults++;
}
// Throw an assertion if query execution fails for any reason.
if (PlanExecutor::FAILURE == state || PlanExecutor::DEAD == state) {
firstBatch.abandon();
error() << "Plan executor error during find command: " << PlanExecutor::statestr(state)
<< ", stats: " << Explain::getWinningPlanStats(exec.get());
return appendCommandStatus(result,
Status(ErrorCodes::OperationFailed,
str::stream()
<< "Executor error during find command: "
<< WorkingSetCommon::toStatusString(obj)));
}
// Before saving the cursor, ensure that whatever plan we established happened with the
// expected collection version
auto css = CollectionShardingState::get(txn, nss);
css->checkShardVersionOrThrow(txn);
// Set up the cursor for getMore.
CursorId cursorId = 0;
if (shouldSaveCursor(txn, collection, state, exec.get())) {
// Register the execution plan inside a ClientCursor. Ownership of the PlanExecutor is
// transferred to the ClientCursor.
//
// First unregister the PlanExecutor so it can be re-registered with ClientCursor.
exec->deregisterExec();
// Create a ClientCursor containing this plan executor. We don't have to worry about
// leaking it as it's inserted into a global map by its ctor.
ClientCursor* cursor =
new ClientCursor(collection->getCursorManager(),
exec.release(),
nss.ns(),
txn->recoveryUnit()->isReadingFromMajorityCommittedSnapshot(),
originalQR.getOptions(),
cmdObj.getOwned());
cursorId = cursor->cursorid();
invariant(!exec);
PlanExecutor* cursorExec = cursor->getExecutor();
// State will be restored on getMore.
cursorExec->saveState();
cursorExec->detachFromOperationContext();
cursor->setLeftoverMaxTimeMicros(txn->getRemainingMaxTimeMicros());
cursor->setPos(numResults);
// Fill out curop based on the results.
endQueryOp(txn, collection, *cursorExec, numResults, cursorId);
} else {
endQueryOp(txn, collection, *exec, numResults, cursorId);
}
// Generate the response object to send to the client.
firstBatch.done(cursorId, nss.ns());
return true;
}
