path: root/src/mongo/db/storage/kv/kv_catalog.cpp

// kv_catalog.cpp


/**
 *    Copyright (C) 2018-present MongoDB, Inc.
 *
 *    This program is free software: you can redistribute it and/or modify
 *    it under the terms of the Server Side Public License, version 1,
 *    as published by MongoDB, Inc.
 *
 *    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
 *    Server Side Public License for more details.
 *
 *    You should have received a copy of the Server Side Public License
 *    along with this program. If not, see
 *    <http://www.mongodb.com/licensing/server-side-public-license>.
 *
 *    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 Server Side 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,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#define MONGO_LOG_DEFAULT_COMPONENT ::mongo::logger::LogComponent::kStorage

#include "mongo/db/storage/kv/kv_catalog.h"

#include <stdlib.h>

#include "mongo/bson/util/bson_extract.h"
#include "mongo/bson/util/builder.h"
#include "mongo/db/concurrency/d_concurrency.h"
#include "mongo/db/namespace_string.h"
#include "mongo/db/operation_context.h"
#include "mongo/db/storage/kv/kv_catalog_feature_tracker.h"
#include "mongo/db/storage/record_store.h"
#include "mongo/db/storage/recovery_unit.h"
#include "mongo/platform/bits.h"
#include "mongo/platform/random.h"
#include "mongo/stdx/memory.h"
#include "mongo/util/log.h"
#include "mongo/util/mongoutils/str.h"

namespace mongo {
namespace {
// This is a global resource, which protects accesses to the catalog metadata (instance-wide).
// It is never used with KVEngines that support doc-level locking so this should never conflict
// with anything else.

const char kIsFeatureDocumentFieldName[] = "isFeatureDoc";
const char kNamespaceFieldName[] = "ns";
const char kNonRepairableFeaturesFieldName[] = "nonRepairable";
const char kRepairableFeaturesFieldName[] = "repairable";
const char kInternalIdentPrefix[] = "internal-";

void appendPositionsOfBitsSet(uint64_t value, StringBuilder* sb) {
    invariant(sb);

    *sb << "[ ";
    bool firstIteration = true;
    while (value) {
        const int lowestSetBitPosition = countTrailingZeros64(value);
        if (!firstIteration) {
            *sb << ", ";
        }
        *sb << lowestSetBitPosition;
        value ^= (1ULL << lowestSetBitPosition);
        firstIteration = false;
    }
    *sb << " ]";
}

// Does not escape letters, digits, '.', or '_'.
// Otherwise escapes to a '.' followed by a zero-filled 2- or 3-digit decimal number.
// Note that this escape table does not produce a 1:1 mapping to and from dbname, and
// collisions are possible.
// For example:
//     "db.123", "db\0143", and "db\073" all escape to "db.123".
//       {'d','b','1','2','3'} => "d" + "b" + "." + "1" + "2" + "3" => "db.123"
//       {'d','b','\x0c','3'}  => "d" + "b" + ".12" + "3"           => "db.123"
//       {'d','b','\x3b'}      => "d" + "b" + ".123"                => "db.123"
constexpr std::array<StringData, 256> escapeTable = {
    ".00"_sd,  ".01"_sd,  ".02"_sd,  ".03"_sd,  ".04"_sd,  ".05"_sd,  ".06"_sd,  ".07"_sd,
    ".08"_sd,  ".09"_sd,  ".10"_sd,  ".11"_sd,  ".12"_sd,  ".13"_sd,  ".14"_sd,  ".15"_sd,
    ".16"_sd,  ".17"_sd,  ".18"_sd,  ".19"_sd,  ".20"_sd,  ".21"_sd,  ".22"_sd,  ".23"_sd,
    ".24"_sd,  ".25"_sd,  ".26"_sd,  ".27"_sd,  ".28"_sd,  ".29"_sd,  ".30"_sd,  ".31"_sd,
    ".32"_sd,  ".33"_sd,  ".34"_sd,  ".35"_sd,  ".36"_sd,  ".37"_sd,  ".38"_sd,  ".39"_sd,
    ".40"_sd,  ".41"_sd,  ".42"_sd,  ".43"_sd,  ".44"_sd,  ".45"_sd,  "."_sd,    ".47"_sd,
    "0"_sd,    "1"_sd,    "2"_sd,    "3"_sd,    "4"_sd,    "5"_sd,    "6"_sd,    "7"_sd,
    "8"_sd,    "9"_sd,    ".58"_sd,  ".59"_sd,  ".60"_sd,  ".61"_sd,  ".62"_sd,  ".63"_sd,
    ".64"_sd,  "A"_sd,    "B"_sd,    "C"_sd,    "D"_sd,    "E"_sd,    "F"_sd,    "G"_sd,
    "H"_sd,    "I"_sd,    "J"_sd,    "K"_sd,    "L"_sd,    "M"_sd,    "N"_sd,    "O"_sd,
    "P"_sd,    "Q"_sd,    "R"_sd,    "S"_sd,    "T"_sd,    "U"_sd,    "V"_sd,    "W"_sd,
    "X"_sd,    "Y"_sd,    "Z"_sd,    ".91"_sd,  ".92"_sd,  ".93"_sd,  ".94"_sd,  "_"_sd,
    ".96"_sd,  "a"_sd,    "b"_sd,    "c"_sd,    "d"_sd,    "e"_sd,    "f"_sd,    "g"_sd,
    "h"_sd,    "i"_sd,    "j"_sd,    "k"_sd,    "l"_sd,    "m"_sd,    "n"_sd,    "o"_sd,
    "p"_sd,    "q"_sd,    "r"_sd,    "s"_sd,    "t"_sd,    "u"_sd,    "v"_sd,    "w"_sd,
    "x"_sd,    "y"_sd,    "z"_sd,    ".123"_sd, ".124"_sd, ".125"_sd, ".126"_sd, ".127"_sd,
    ".128"_sd, ".129"_sd, ".130"_sd, ".131"_sd, ".132"_sd, ".133"_sd, ".134"_sd, ".135"_sd,
    ".136"_sd, ".137"_sd, ".138"_sd, ".139"_sd, ".140"_sd, ".141"_sd, ".142"_sd, ".143"_sd,
    ".144"_sd, ".145"_sd, ".146"_sd, ".147"_sd, ".148"_sd, ".149"_sd, ".150"_sd, ".151"_sd,
    ".152"_sd, ".153"_sd, ".154"_sd, ".155"_sd, ".156"_sd, ".157"_sd, ".158"_sd, ".159"_sd,
    ".160"_sd, ".161"_sd, ".162"_sd, ".163"_sd, ".164"_sd, ".165"_sd, ".166"_sd, ".167"_sd,
    ".168"_sd, ".169"_sd, ".170"_sd, ".171"_sd, ".172"_sd, ".173"_sd, ".174"_sd, ".175"_sd,
    ".176"_sd, ".177"_sd, ".178"_sd, ".179"_sd, ".180"_sd, ".181"_sd, ".182"_sd, ".183"_sd,
    ".184"_sd, ".185"_sd, ".186"_sd, ".187"_sd, ".188"_sd, ".189"_sd, ".190"_sd, ".191"_sd,
    ".192"_sd, ".193"_sd, ".194"_sd, ".195"_sd, ".196"_sd, ".197"_sd, ".198"_sd, ".199"_sd,
    ".200"_sd, ".201"_sd, ".202"_sd, ".203"_sd, ".204"_sd, ".205"_sd, ".206"_sd, ".207"_sd,
    ".208"_sd, ".209"_sd, ".210"_sd, ".211"_sd, ".212"_sd, ".213"_sd, ".214"_sd, ".215"_sd,
    ".216"_sd, ".217"_sd, ".218"_sd, ".219"_sd, ".220"_sd, ".221"_sd, ".222"_sd, ".223"_sd,
    ".224"_sd, ".225"_sd, ".226"_sd, ".227"_sd, ".228"_sd, ".229"_sd, ".230"_sd, ".231"_sd,
    ".232"_sd, ".233"_sd, ".234"_sd, ".235"_sd, ".236"_sd, ".237"_sd, ".238"_sd, ".239"_sd,
    ".240"_sd, ".241"_sd, ".242"_sd, ".243"_sd, ".244"_sd, ".245"_sd, ".246"_sd, ".247"_sd,
    ".248"_sd, ".249"_sd, ".250"_sd, ".251"_sd, ".252"_sd, ".253"_sd, ".254"_sd, ".255"_sd};

std::string escapeDbName(StringData dbname) {
    std::string escaped;
    escaped.reserve(dbname.size());
    for (unsigned char c : dbname) {
        StringData ce = escapeTable[c];
        escaped.append(ce.begin(), ce.end());
    }
    return escaped;
}

}  // namespace

using std::unique_ptr;
using std::string;

class KVCatalog::AddIdentChange : public RecoveryUnit::Change {
public:
    AddIdentChange(KVCatalog* catalog, StringData ident)
        : _catalog(catalog), _ident(ident.toString()) {}

    virtual void commit(boost::optional<Timestamp>) {}
    virtual void rollback() {
        stdx::lock_guard<stdx::mutex> lk(_catalog->_identsLock);
        _catalog->_idents.erase(_ident);
    }

    KVCatalog* const _catalog;
    const std::string _ident;
};

class KVCatalog::RemoveIdentChange : public RecoveryUnit::Change {
public:
    RemoveIdentChange(KVCatalog* catalog, StringData ident, const Entry& entry)
        : _catalog(catalog), _ident(ident.toString()), _entry(entry) {}

    virtual void commit(boost::optional<Timestamp>) {}
    virtual void rollback() {
        stdx::lock_guard<stdx::mutex> lk(_catalog->_identsLock);
        _catalog->_idents[_ident] = _entry;
    }

    KVCatalog* const _catalog;
    const std::string _ident;
    const Entry _entry;
};

bool KVCatalog::FeatureTracker::isFeatureDocument(BSONObj obj) {
    BSONElement firstElem = obj.firstElement();
    if (firstElem.fieldNameStringData() == kIsFeatureDocumentFieldName) {
        return firstElem.booleanSafe();
    }
    return false;
}

Status KVCatalog::FeatureTracker::isCompatibleWithCurrentCode(OperationContext* opCtx) const {
    FeatureBits versionInfo = getInfo(opCtx);

    uint64_t unrecognizedNonRepairableFeatures =
        versionInfo.nonRepairableFeatures & ~_usedNonRepairableFeaturesMask;
    if (unrecognizedNonRepairableFeatures) {
        StringBuilder sb;
        sb << "The data files use features not recognized by this version of mongod; the NR feature"
              " bits in positions ";
        appendPositionsOfBitsSet(unrecognizedNonRepairableFeatures, &sb);
        sb << " aren't recognized by this version of mongod";
        return {ErrorCodes::MustUpgrade, sb.str()};
    }

    uint64_t unrecognizedRepairableFeatures =
        versionInfo.repairableFeatures & ~_usedRepairableFeaturesMask;
    if (unrecognizedRepairableFeatures) {
        StringBuilder sb;
        sb << "The data files use features not recognized by this version of mongod; the R feature"
              " bits in positions ";
        appendPositionsOfBitsSet(unrecognizedRepairableFeatures, &sb);
        sb << " aren't recognized by this version of mongod";
        return {ErrorCodes::CanRepairToDowngrade, sb.str()};
    }

    return Status::OK();
}

std::unique_ptr<KVCatalog::FeatureTracker> KVCatalog::FeatureTracker::get(OperationContext* opCtx,
                                                                          KVCatalog* catalog,
                                                                          RecordId rid) {
    auto record = catalog->_rs->dataFor(opCtx, rid);
    BSONObj obj = record.toBson();
    invariant(isFeatureDocument(obj));
    return std::unique_ptr<KVCatalog::FeatureTracker>(new KVCatalog::FeatureTracker(catalog, rid));
}

std::unique_ptr<KVCatalog::FeatureTracker> KVCatalog::FeatureTracker::create(
    OperationContext* opCtx, KVCatalog* catalog) {
    return std::unique_ptr<KVCatalog::FeatureTracker>(
        new KVCatalog::FeatureTracker(catalog, RecordId()));
}

bool KVCatalog::FeatureTracker::isNonRepairableFeatureInUse(OperationContext* opCtx,
                                                            NonRepairableFeature feature) const {
    FeatureBits versionInfo = getInfo(opCtx);
    return versionInfo.nonRepairableFeatures & static_cast<NonRepairableFeatureMask>(feature);
}

void KVCatalog::FeatureTracker::markNonRepairableFeatureAsInUse(OperationContext* opCtx,
                                                                NonRepairableFeature feature) {
    FeatureBits versionInfo = getInfo(opCtx);
    versionInfo.nonRepairableFeatures |= static_cast<NonRepairableFeatureMask>(feature);
    putInfo(opCtx, versionInfo);
}

void KVCatalog::FeatureTracker::markNonRepairableFeatureAsNotInUse(OperationContext* opCtx,
                                                                   NonRepairableFeature feature) {
    FeatureBits versionInfo = getInfo(opCtx);
    versionInfo.nonRepairableFeatures &= ~static_cast<NonRepairableFeatureMask>(feature);
    putInfo(opCtx, versionInfo);
}

bool KVCatalog::FeatureTracker::isRepairableFeatureInUse(OperationContext* opCtx,
                                                         RepairableFeature feature) const {
    FeatureBits versionInfo = getInfo(opCtx);
    return versionInfo.repairableFeatures & static_cast<RepairableFeatureMask>(feature);
}

void KVCatalog::FeatureTracker::markRepairableFeatureAsInUse(OperationContext* opCtx,
                                                             RepairableFeature feature) {
    FeatureBits versionInfo = getInfo(opCtx);
    versionInfo.repairableFeatures |= static_cast<RepairableFeatureMask>(feature);
    putInfo(opCtx, versionInfo);
}

void KVCatalog::FeatureTracker::markRepairableFeatureAsNotInUse(OperationContext* opCtx,
                                                                RepairableFeature feature) {
    FeatureBits versionInfo = getInfo(opCtx);
    versionInfo.repairableFeatures &= ~static_cast<RepairableFeatureMask>(feature);
    putInfo(opCtx, versionInfo);
}

KVCatalog::FeatureTracker::FeatureBits KVCatalog::FeatureTracker::getInfo(
    OperationContext* opCtx) const {
    if (_rid.isNull()) {
        return {};
    }

    auto record = _catalog->_rs->dataFor(opCtx, _rid);
    BSONObj obj = record.toBson();
    invariant(isFeatureDocument(obj));

    BSONElement nonRepairableFeaturesElem;
    auto nonRepairableFeaturesStatus = bsonExtractTypedField(
        obj, kNonRepairableFeaturesFieldName, BSONType::NumberLong, &nonRepairableFeaturesElem);
    if (!nonRepairableFeaturesStatus.isOK()) {
        error() << "error: exception extracting typed field with obj:" << redact(obj);
        fassert(40111, nonRepairableFeaturesStatus);
    }

    BSONElement repairableFeaturesElem;
    auto repairableFeaturesStatus = bsonExtractTypedField(
        obj, kRepairableFeaturesFieldName, BSONType::NumberLong, &repairableFeaturesElem);
    if (!repairableFeaturesStatus.isOK()) {
        error() << "error: exception extracting typed field with obj:" << redact(obj);
        fassert(40112, repairableFeaturesStatus);
    }

    FeatureBits versionInfo;
    versionInfo.nonRepairableFeatures =
        static_cast<NonRepairableFeatureMask>(nonRepairableFeaturesElem.numberLong());
    versionInfo.repairableFeatures =
        static_cast<RepairableFeatureMask>(repairableFeaturesElem.numberLong());
    return versionInfo;
}

void KVCatalog::FeatureTracker::putInfo(OperationContext* opCtx, const FeatureBits& versionInfo) {
    BSONObjBuilder bob;
    bob.appendBool(kIsFeatureDocumentFieldName, true);
    // We intentionally include the "ns" field with a null value in the feature document to prevent
    // older versions that do 'obj["ns"].String()' from starting up. This way only versions that are
    // aware of the feature document's existence can successfully start up.
    bob.appendNull(kNamespaceFieldName);
    bob.append(kNonRepairableFeaturesFieldName,
               static_cast<long long>(versionInfo.nonRepairableFeatures));
    bob.append(kRepairableFeaturesFieldName,
               static_cast<long long>(versionInfo.repairableFeatures));
    BSONObj obj = bob.done();

    if (_rid.isNull()) {
        // This is the first time a feature is being marked as in-use or not in-use, so we must
        // insert the feature document rather than update it.
        auto rid = _catalog->_rs->insertRecord(opCtx, obj.objdata(), obj.objsize(), Timestamp());
        fassert(40113, rid.getStatus());
        _rid = rid.getValue();
    } else {
        auto status = _catalog->_rs->updateRecord(opCtx, _rid, obj.objdata(), obj.objsize());
        fassert(40114, status);
    }
}

KVCatalog::KVCatalog(RecordStore* rs, bool directoryPerDb, bool directoryForIndexes)
    : _rs(rs),
      _directoryPerDb(directoryPerDb),
      _directoryForIndexes(directoryForIndexes),
      _rand(_newRand()) {}

KVCatalog::~KVCatalog() {
    _rs = NULL;
}

std::string KVCatalog::_newRand() {
    return str::stream() << std::unique_ptr<SecureRandom>(SecureRandom::create())->nextInt64();
}

bool KVCatalog::_hasEntryCollidingWithRand() const {
    // Only called from init() so don't need to lock.
    for (NSToIdentMap::const_iterator it = _idents.begin(); it != _idents.end(); ++it) {
        if (StringData(it->first).endsWith(_rand))
            return true;
    }
    return false;
}

std::string KVCatalog::newInternalIdent() {
    StringBuilder buf;
    buf << kInternalIdentPrefix;
    buf << _next.fetchAndAdd(1) << '-' << _rand;
    return buf.str();
}

std::string KVCatalog::getFilesystemPathForDb(const std::string& dbName) const {
    if (_directoryPerDb) {
        return storageGlobalParams.dbpath + '/' + escapeDbName(dbName);
    } else {
        return storageGlobalParams.dbpath;
    }
}

std::string KVCatalog::_newUniqueIdent(StringData ns, const char* kind) {
    // If this changes to not put _rand at the end, _hasEntryCollidingWithRand will need fixing.
    StringBuilder buf;
    if (_directoryPerDb) {
        buf << escapeDbName(nsToDatabaseSubstring(ns)) << '/';
    }
    buf << kind;
    buf << (_directoryForIndexes ? '/' : '-');
    buf << _next.fetchAndAdd(1) << '-' << _rand;
    return buf.str();
}

void KVCatalog::init(OperationContext* opCtx) {
    // No locking needed since called single threaded.
    auto cursor = _rs->getCursor(opCtx);
    while (auto record = cursor->next()) {
        BSONObj obj = record->data.releaseToBson();

        if (FeatureTracker::isFeatureDocument(obj)) {
            // There should be at most one version document in the catalog.
            invariant(!_featureTracker);

            // Initialize the feature tracker and skip over the version document because it doesn't
            // correspond to a namespace entry.
            _featureTracker = FeatureTracker::get(opCtx, this, record->id);
            continue;
        }

        // No rollback since this is just loading already committed data.
        string ns = obj["ns"].String();
        string ident = obj["ident"].String();
        _idents[ns] = Entry(ident, record->id);
    }

    if (!_featureTracker) {
        // If there wasn't a feature document, then just an initialize a feature tracker that
        // doesn't manage a feature document yet.
        _featureTracker = KVCatalog::FeatureTracker::create(opCtx, this);
    }

    // In the unlikely event that we have used this _rand before generate a new one.
    while (_hasEntryCollidingWithRand()) {
        _rand = _newRand();
    }
}

void KVCatalog::getAllCollections(std::vector<std::string>* out) const {
    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    for (NSToIdentMap::const_iterator it = _idents.begin(); it != _idents.end(); ++it) {
        out->push_back(it->first);
    }
}

Status KVCatalog::newCollection(OperationContext* opCtx,
                                StringData ns,
                                const CollectionOptions& options,
                                KVPrefix prefix) {
    invariant(opCtx->lockState()->isDbLockedForMode(nsToDatabaseSubstring(ns), MODE_X));

    const string ident = _newUniqueIdent(ns, "collection");

    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    Entry& old = _idents[ns.toString()];
    if (!old.ident.empty()) {
        return Status(ErrorCodes::NamespaceExists, "collection already exists");
    }

    opCtx->recoveryUnit()->registerChange(new AddIdentChange(this, ns));

    BSONObj obj;
    {
        BSONObjBuilder b;
        b.append("ns", ns);
        b.append("ident", ident);
        BSONCollectionCatalogEntry::MetaData md;
        md.ns = ns.toString();
        md.options = options;
        md.prefix = prefix;
        b.append("md", md.toBSON());
        obj = b.obj();
    }
    StatusWith<RecordId> res = _rs->insertRecord(opCtx, obj.objdata(), obj.objsize(), Timestamp());
    if (!res.isOK())
        return res.getStatus();

    old = Entry(ident, res.getValue());
    LOG(1) << "stored meta data for " << ns << " @ " << res.getValue();
    return Status::OK();
}

std::string KVCatalog::getCollectionIdent(StringData ns) const {
    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    NSToIdentMap::const_iterator it = _idents.find(ns.toString());
    invariant(it != _idents.end());
    return it->second.ident;
}

std::string KVCatalog::getIndexIdent(OperationContext* opCtx,
                                     StringData ns,
                                     StringData idxName) const {
    BSONObj obj = _findEntry(opCtx, ns);
    BSONObj idxIdent = obj["idxIdent"].Obj();
    return idxIdent[idxName].String();
}

BSONObj KVCatalog::_findEntry(OperationContext* opCtx, StringData ns, RecordId* out) const {
    RecordId dl;
    {
        stdx::lock_guard<stdx::mutex> lk(_identsLock);
        NSToIdentMap::const_iterator it = _idents.find(ns.toString());
        invariant(it != _idents.end(), str::stream() << "Did not find collection. Ns: " << ns);
        dl = it->second.storedLoc;
    }

    LOG(3) << "looking up metadata for: " << ns << " @ " << dl;
    RecordData data;
    if (!_rs->findRecord(opCtx, dl, &data)) {
        // since the in memory meta data isn't managed with mvcc
        // its possible for different transactions to see slightly
        // different things, which is ok via the locking above.
        return BSONObj();
    }

    if (out)
        *out = dl;

    return data.releaseToBson().getOwned();
}

BSONCollectionCatalogEntry::MetaData KVCatalog::getMetaData(OperationContext* opCtx,
                                                            StringData ns) const {
    BSONObj obj = _findEntry(opCtx, ns);
    LOG(3) << " fetched CCE metadata: " << obj;
    BSONCollectionCatalogEntry::MetaData md;
    const BSONElement mdElement = obj["md"];
    if (mdElement.isABSONObj()) {
        LOG(3) << "returning metadata: " << mdElement;
        md.parse(mdElement.Obj());
    }
    return md;
}

void KVCatalog::putMetaData(OperationContext* opCtx,
                            StringData ns,
                            BSONCollectionCatalogEntry::MetaData& md) {
    RecordId loc;
    BSONObj obj = _findEntry(opCtx, ns, &loc);

    {
        // rebuilt doc
        BSONObjBuilder b;
        b.append("md", md.toBSON());

        BSONObjBuilder newIdentMap;
        BSONObj oldIdentMap;
        if (obj["idxIdent"].isABSONObj())
            oldIdentMap = obj["idxIdent"].Obj();

        // fix ident map
        for (size_t i = 0; i < md.indexes.size(); i++) {
            string name = md.indexes[i].name();
            BSONElement e = oldIdentMap[name];
            if (e.type() == String) {
                newIdentMap.append(e);
                continue;
            }
            // missing, create new
            newIdentMap.append(name, _newUniqueIdent(ns, "index"));
        }
        b.append("idxIdent", newIdentMap.obj());

        // add whatever is left
        b.appendElementsUnique(obj);
        obj = b.obj();
    }

    LOG(3) << "recording new metadata: " << obj;
    Status status = _rs->updateRecord(opCtx, loc, obj.objdata(), obj.objsize());
    fassert(28521, status.isOK());
}

Status KVCatalog::renameCollection(OperationContext* opCtx,
                                   StringData fromNS,
                                   StringData toNS,
                                   bool stayTemp) {
    RecordId loc;
    BSONObj old = _findEntry(opCtx, fromNS, &loc).getOwned();
    {
        BSONObjBuilder b;

        b.append("ns", toNS);

        BSONCollectionCatalogEntry::MetaData md;
        md.parse(old["md"].Obj());
        md.rename(toNS);
        if (!stayTemp)
            md.options.temp = false;
        b.append("md", md.toBSON());

        b.appendElementsUnique(old);

        BSONObj obj = b.obj();
        Status status = _rs->updateRecord(opCtx, loc, obj.objdata(), obj.objsize());
        fassert(28522, status.isOK());
    }

    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    const NSToIdentMap::iterator fromIt = _idents.find(fromNS.toString());
    invariant(fromIt != _idents.end());

    opCtx->recoveryUnit()->registerChange(new RemoveIdentChange(this, fromNS, fromIt->second));
    opCtx->recoveryUnit()->registerChange(new AddIdentChange(this, toNS));

    _idents.erase(fromIt);
    _idents[toNS.toString()] = Entry(old["ident"].String(), loc);

    return Status::OK();
}

Status KVCatalog::dropCollection(OperationContext* opCtx, StringData ns) {
    invariant(opCtx->lockState()->isDbLockedForMode(nsToDatabaseSubstring(ns), MODE_X));
    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    const NSToIdentMap::iterator it = _idents.find(ns.toString());
    if (it == _idents.end()) {
        return Status(ErrorCodes::NamespaceNotFound, "collection not found");
    }

    opCtx->recoveryUnit()->registerChange(new RemoveIdentChange(this, ns, it->second));

    LOG(1) << "deleting metadata for " << ns << " @ " << it->second.storedLoc;
    _rs->deleteRecord(opCtx, it->second.storedLoc);
    _idents.erase(it);

    return Status::OK();
}

std::vector<std::string> KVCatalog::getAllIdentsForDB(StringData db) const {
    std::vector<std::string> v;

    {
        stdx::lock_guard<stdx::mutex> lk(_identsLock);
        for (NSToIdentMap::const_iterator it = _idents.begin(); it != _idents.end(); ++it) {
            NamespaceString ns(it->first);
            if (ns.db() != db)
                continue;
            v.push_back(it->second.ident);
        }
    }

    return v;
}

std::vector<std::string> KVCatalog::getAllIdents(OperationContext* opCtx) const {
    std::vector<std::string> v;

    auto cursor = _rs->getCursor(opCtx);
    while (auto record = cursor->next()) {
        BSONObj obj = record->data.releaseToBson();
        if (FeatureTracker::isFeatureDocument(obj)) {
            // Skip over the version document because it doesn't correspond to a namespace entry and
            // therefore doesn't refer to any idents.
            continue;
        }
        v.push_back(obj["ident"].String());

        BSONElement e = obj["idxIdent"];
        if (!e.isABSONObj())
            continue;
        BSONObj idxIdent = e.Obj();

        BSONObjIterator sub(idxIdent);
        while (sub.more()) {
            BSONElement e = sub.next();
            v.push_back(e.String());
        }
    }

    return v;
}

bool KVCatalog::isUserDataIdent(StringData ident) const {
    // Indexes and collections are candidates for dropping when the storage engine's metadata does
    // not align with the catalog metadata.
    return ident.find("index-") != std::string::npos || ident.find("index/") != std::string::npos ||
        ident.find("collection-") != std::string::npos ||
        ident.find("collection/") != std::string::npos;
}

bool KVCatalog::isInternalIdent(StringData ident) const {
    return ident.find(kInternalIdentPrefix) != std::string::npos;
}

bool KVCatalog::isCollectionIdent(StringData ident) const {
    // Internal idents prefixed "internal-" should not be considered collections, because
    // they are not eligible for orphan recovery through repair.
    return ident.find("collection-") != std::string::npos ||
        ident.find("collection/") != std::string::npos;
}

StatusWith<std::string> KVCatalog::newOrphanedIdent(OperationContext* opCtx, std::string ident) {
    // The collection will be named local.orphan.xxxxx.
    std::string identNs = ident;
    std::replace(identNs.begin(), identNs.end(), '-', '_');
    std::string ns = NamespaceString(NamespaceString::kOrphanCollectionDb,
                                     NamespaceString::kOrphanCollectionPrefix + identNs)
                         .ns();

    stdx::lock_guard<stdx::mutex> lk(_identsLock);
    Entry& old = _idents[ns];
    if (!old.ident.empty()) {
        return Status(ErrorCodes::NamespaceExists,
                      str::stream() << ns << " already exists in the catalog");
    }
    opCtx->recoveryUnit()->registerChange(new AddIdentChange(this, ns));

    // Generate a new UUID for the orphaned collection.
    CollectionOptions optionsWithUUID;
    optionsWithUUID.uuid.emplace(CollectionUUID::gen());
    BSONObj obj;
    {
        BSONObjBuilder b;
        b.append("ns", ns);
        b.append("ident", ident);
        BSONCollectionCatalogEntry::MetaData md;
        md.ns = ns;
        // Default options with newly generated UUID.
        md.options = optionsWithUUID;
        // Not Prefixed.
        md.prefix = KVPrefix::kNotPrefixed;
        b.append("md", md.toBSON());
        obj = b.obj();
    }
    StatusWith<RecordId> res = _rs->insertRecord(opCtx, obj.objdata(), obj.objsize(), Timestamp());
    if (!res.isOK())
        return res.getStatus();

    old = Entry(ident, res.getValue());
    LOG(1) << "stored meta data for orphaned collection " << ns << " @ " << res.getValue();
    return StatusWith<std::string>(std::move(ns));
}
}