Status WriteCmd::explain(OperationContext* txn,
const std::string& dbname,
const BSONObj& cmdObj,
ExplainCommon::Verbosity verbosity,
BSONObjBuilder* out) const {
// For now we only explain update and delete write commands.
if ( BatchedCommandRequest::BatchType_Update != _writeType &&
BatchedCommandRequest::BatchType_Delete != _writeType ) {
return Status( ErrorCodes::IllegalOperation,
"Only update and delete write ops can be explained" );
}
// Parse the batch request.
BatchedCommandRequest request( _writeType );
std::string errMsg;
if ( !request.parseBSON( cmdObj, &errMsg ) || !request.isValid( &errMsg ) ) {
return Status( ErrorCodes::FailedToParse, errMsg );
}
// Note that this is a runCommmand, and therefore, the database and the collection name
// are in different parts of the grammar for the command. But it's more convenient to
// work with a NamespaceString. We built it here and replace it in the parsed command.
// Internally, everything work with the namespace string as opposed to just the
// collection name.
NamespaceString nsString(dbname, request.getNS());
request.setNSS(nsString);
// Do the validation of the batch that is shared with non-explained write batches.
Status isValid = WriteBatchExecutor::validateBatch( request );
if (!isValid.isOK()) {
return isValid;
}
// Explain must do one additional piece of validation: For now we only explain
// singleton batches.
if ( request.sizeWriteOps() != 1u ) {
return Status( ErrorCodes::InvalidLength,
"explained write batches must be of size 1" );
}
// Get a reference to the singleton batch item (it's the 0th item in the batch).
BatchItemRef batchItem( &request, 0 );
if ( BatchedCommandRequest::BatchType_Update == _writeType ) {
// Create the update request.
UpdateRequest updateRequest( nsString );
updateRequest.setQuery( batchItem.getUpdate()->getQuery() );
updateRequest.setUpdates( batchItem.getUpdate()->getUpdateExpr() );
updateRequest.setMulti( batchItem.getUpdate()->getMulti() );
updateRequest.setUpsert( batchItem.getUpdate()->getUpsert() );
updateRequest.setUpdateOpLog( true );
UpdateLifecycleImpl updateLifecycle( true, updateRequest.getNamespaceString() );
updateRequest.setLifecycle( &updateLifecycle );
updateRequest.setExplain();
// Explained updates can yield.
updateRequest.setYieldPolicy(PlanExecutor::YIELD_AUTO);
OpDebug* debug = &txn->getCurOp()->debug();
ParsedUpdate parsedUpdate( txn, &updateRequest );
Status parseStatus = parsedUpdate.parseRequest();
if ( !parseStatus.isOK() ) {
return parseStatus;
}
// Explains of write commands are read-only, but we take write locks so
// that timing info is more accurate.
AutoGetDb autoDb( txn, nsString.db(), MODE_IX );
Lock::CollectionLock colLock( txn->lockState(), nsString.ns(), MODE_IX );
// We check the shard version explicitly here rather than using Client::Context,
// as Context can do implicit database creation if the db does not exist. We want
// explain to be a no-op that reports a trivial EOF plan against non-existent dbs
// or collections.
ensureShardVersionOKOrThrow( nsString.ns() );
// Get a pointer to the (possibly NULL) collection.
Collection* collection = NULL;
if ( autoDb.getDb() ) {
collection = autoDb.getDb()->getCollection( txn, nsString.ns() );
}
PlanExecutor* rawExec;
uassertStatusOK(getExecutorUpdate(txn, collection, &parsedUpdate, debug, &rawExec));
boost::scoped_ptr<PlanExecutor> exec(rawExec);
// Explain the plan tree.
Explain::explainStages( exec.get(), verbosity, out );
return Status::OK();
}
else {
invariant( BatchedCommandRequest::BatchType_Delete == _writeType );
// Create the delete request.
DeleteRequest deleteRequest( nsString );
deleteRequest.setQuery( batchItem.getDelete()->getQuery() );
deleteRequest.setMulti( batchItem.getDelete()->getLimit() != 1 );
deleteRequest.setUpdateOpLog(true);
deleteRequest.setGod( false );
deleteRequest.setExplain();
// Explained deletes can yield.
deleteRequest.setYieldPolicy(PlanExecutor::YIELD_AUTO);
ParsedDelete parsedDelete(txn, &deleteRequest);
Status parseStatus = parsedDelete.parseRequest();
if (!parseStatus.isOK()) {
return parseStatus;
}
// Explains of write commands are read-only, but we take write locks so that timing
// info is more accurate.
AutoGetDb autoDb(txn, nsString.db(), MODE_IX);
Lock::CollectionLock colLock(txn->lockState(), nsString.ns(), MODE_IX);
// We check the shard version explicitly here rather than using Client::Context,
// as Context can do implicit database creation if the db does not exist. We want
// explain to be a no-op that reports a trivial EOF plan against non-existent dbs
// or collections.
ensureShardVersionOKOrThrow( nsString.ns() );
// Get a pointer to the (possibly NULL) collection.
Collection* collection = NULL;
if (autoDb.getDb()) {
collection = autoDb.getDb()->getCollection(txn, nsString.ns());
}
PlanExecutor* rawExec;
uassertStatusOK(getExecutorDelete(txn, collection, &parsedDelete, &rawExec));
boost::scoped_ptr<PlanExecutor> exec(rawExec);
// Explain the plan tree.
Explain::explainStages(exec.get(), verbosity, out);
return Status::OK();
}
}
Status WriteCmd::explain(OperationContext* txn,
const std::string& dbname,
const BSONObj& cmdObj,
ExplainCommon::Verbosity verbosity,
BSONObjBuilder* out) const {
// For now we only explain update and delete write commands.
if ( BatchedCommandRequest::BatchType_Update != _writeType &&
BatchedCommandRequest::BatchType_Delete != _writeType ) {
return Status( ErrorCodes::IllegalOperation,
"Only update and delete write ops can be explained" );
}
// Parse the batch request.
BatchedCommandRequest request( _writeType );
std::string errMsg;
if ( !request.parseBSON( cmdObj, &errMsg ) || !request.isValid( &errMsg ) ) {
return Status( ErrorCodes::FailedToParse, errMsg );
}
// Note that this is a runCommmand, and therefore, the database and the collection name
// are in different parts of the grammar for the command. But it's more convenient to
// work with a NamespaceString. We built it here and replace it in the parsed command.
// Internally, everything work with the namespace string as opposed to just the
// collection name.
NamespaceString nsString(dbname, request.getNS());
request.setNS(nsString.ns());
// Do the validation of the batch that is shared with non-explained write batches.
Status isValid = WriteBatchExecutor::validateBatch( request );
if (!isValid.isOK()) {
return isValid;
}
// Explain must do one additional piece of validation: For now we only explain
// singleton batches.
if ( request.sizeWriteOps() != 1u ) {
return Status( ErrorCodes::InvalidLength,
"explained write batches must be of size 1" );
}
// Get a reference to the singleton batch item (it's the 0th item in the batch).
BatchItemRef batchItem( &request, 0 );
if ( BatchedCommandRequest::BatchType_Update == _writeType ) {
// Create the update request.
UpdateRequest updateRequest( txn, nsString );
updateRequest.setQuery( batchItem.getUpdate()->getQuery() );
updateRequest.setUpdates( batchItem.getUpdate()->getUpdateExpr() );
updateRequest.setMulti( batchItem.getUpdate()->getMulti() );
updateRequest.setUpsert( batchItem.getUpdate()->getUpsert() );
updateRequest.setUpdateOpLog( true );
UpdateLifecycleImpl updateLifecycle( true, updateRequest.getNamespaceString() );
updateRequest.setLifecycle( &updateLifecycle );
updateRequest.setExplain();
// Explained updates can yield.
updateRequest.setYieldPolicy(PlanExecutor::YIELD_AUTO);
// Use the request to create an UpdateExecutor, and from it extract the
// plan tree which will be used to execute this update.
UpdateExecutor updateExecutor( &updateRequest, &txn->getCurOp()->debug() );
Status prepStatus = updateExecutor.prepare();
if ( !prepStatus.isOK() ) {
return prepStatus;
}
// Explains of write commands are read-only, but we take an exclusive lock so
// that timing info is more accurate.
Lock::DBLock dlk(txn->lockState(), nsString.db(), MODE_IX);
Client::Context ctx(txn, nsString);
Status prepInLockStatus = updateExecutor.prepareInLock(ctx.db());
if ( !prepInLockStatus.isOK() ) {
return prepInLockStatus;
}
// Executor registration and yield policy is handled internally by the update executor.
PlanExecutor* exec = updateExecutor.getPlanExecutor();
// Explain the plan tree.
return Explain::explainStages( exec, verbosity, out );
}
else {
invariant( BatchedCommandRequest::BatchType_Delete == _writeType );
// Create the delete request.
DeleteRequest deleteRequest( txn, nsString );
deleteRequest.setQuery( batchItem.getDelete()->getQuery() );
deleteRequest.setMulti( batchItem.getDelete()->getLimit() != 1 );
deleteRequest.setUpdateOpLog(true);
deleteRequest.setGod( false );
deleteRequest.setExplain();
// Explained deletes can yield.
deleteRequest.setYieldPolicy(PlanExecutor::YIELD_AUTO);
// Use the request to create a DeleteExecutor, and from it extract the
// plan tree which will be used to execute this update.
DeleteExecutor deleteExecutor( &deleteRequest );
Status prepStatus = deleteExecutor.prepare();
if ( !prepStatus.isOK() ) {
return prepStatus;
}
// Explains of write commands are read-only, but we take a write lock so that timing
// info is more accurate.
Lock::DBLock dlk(txn->lockState(), nsString.db(), MODE_IX);
Client::Context ctx(txn, nsString);
Status prepInLockStatus = deleteExecutor.prepareInLock(ctx.db());
if ( !prepInLockStatus.isOK()) {
return prepInLockStatus;
}
// Executor registration and yield policy is handled internally by the delete executor.
PlanExecutor* exec = deleteExecutor.getPlanExecutor();
// Explain the plan tree.
return Explain::explainStages( exec, verbosity, out );
}
}