find_cmd.cpp

/**
 *    Copyright (C) 2014 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
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 */

#include "mongo/platform/basic.h"

#include "mongo/db/commands/find_cmd.h"

#include <boost/scoped_ptr.hpp>

#include "mongo/db/auth/authorization_session.h"
#include "mongo/db/catalog/collection.h"
#include "mongo/db/catalog/database.h"
#include "mongo/db/client.h"
#include "mongo/db/commands.h"
#include "mongo/db/query/explain.h"
#include "mongo/db/query/get_executor.h"
#include "mongo/db/query/find.h"
#include "mongo/s/d_state.h"

namespace mongo {

    using boost::scoped_ptr;
    using std::auto_ptr;
    using std::string;

    static FindCmd findCmd;

    Status FindCmd::checkAuthForCommand(ClientBasic* client,
                                           const std::string& dbname,
                                           const BSONObj& cmdObj) {
        AuthorizationSession* authzSession = client->getAuthorizationSession();
        ResourcePattern pattern = parseResourcePattern(dbname, cmdObj);

        if (authzSession->isAuthorizedForActionsOnResource(pattern, ActionType::find)) {
            return Status::OK();
        }

        return Status(ErrorCodes::Unauthorized, "unauthorized");
    }

    Status FindCmd::explain(OperationContext* txn,
                             const std::string& dbname,
                             const BSONObj& cmdObj,
                             ExplainCommon::Verbosity verbosity,
                             BSONObjBuilder* out) const {
        const string fullns = parseNs(dbname, cmdObj);

        // Parse the command BSON to a LiteParsedQuery.
        LiteParsedQuery* rawLpq;
        bool isExplain = true;
        Status lpqStatus = LiteParsedQuery::make(fullns, cmdObj, isExplain, &rawLpq);
        if (!lpqStatus.isOK()) {
            return lpqStatus;
        }
        auto_ptr<LiteParsedQuery> lpq(rawLpq);

        const NamespaceString nss(fullns);

        // Finish the parsing step by using the LiteParsedQuery to create a CanonicalQuery.
        // This requires a lock on the collection in case we're parsing $where: where-specific
        // parsing code assumes we have a lock and creates execution machinery that requires it.
        CanonicalQuery* rawCq;
        WhereCallbackReal whereCallback(txn, nss.db());
        Status canonStatus = CanonicalQuery::canonicalize(lpq.release(), &rawCq, whereCallback);
        if (!canonStatus.isOK()) {
            return canonStatus;
        }
        auto_ptr<CanonicalQuery> cq(rawCq);

        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.
        PlanExecutor* rawExec;
        Status execStatus = Status::OK();
        if (cq->getParsed().isOplogReplay()) {
            execStatus = getOplogStartHack(txn, collection, cq.release(), &rawExec);
        }
        else {
            size_t options = QueryPlannerParams::DEFAULT;
            // TODO: The version attached to the TLS cannot be relied upon, the shard
            // version should be passed as part of the command parameter.
            if (shardingState.needCollectionMetadata(cq->getParsed().ns())) {
                options |= QueryPlannerParams::INCLUDE_SHARD_FILTER;
            }

            execStatus = getExecutor(txn,
                                     collection,
                                     cq.release(),
                                     PlanExecutor::YIELD_AUTO,
                                     &rawExec,
                                     options);
        }

        if (!execStatus.isOK()) {
            return execStatus;
        }

        scoped_ptr<PlanExecutor> exec(rawExec);

        // Got the execution tree. Explain it.
        Explain::explainStages(exec.get(), verbosity, out);
        return Status::OK();
    }

    bool FindCmd::run(OperationContext* txn,
                         const string& dbname,
                         BSONObj& cmdObj, int options,
                         string& errmsg,
                         BSONObjBuilder& result,
                         bool fromRepl) {
        // Currently only explains of finds run through the find command. Queries that are not
        // explained use the legacy OP_QUERY path.
        // TODO: check the comment above regarding shard versioning.
        errmsg = "find command not yet implemented";
        return false;
    }

} // namespace mongo