namespace.h

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// namespace.h

#pragma once

#include "../pch.h"
#include "jsobj.h"
#include "queryutil.h"
#include "diskloc.h"
#include "../util/hashtab.h"
#include "mongommf.h"

namespace mongo {

    /* in the mongo source code, "client" means "database". */

    const int MaxDatabaseNameLen = 256; // max str len for the db name, including null char

    /* e.g.
       NamespaceString ns("acme.orders");
       cout << ns.coll; // "orders"
    */
    class NamespaceString {
    public:
        string db;
        string coll; // note collection names can have periods in them for organizing purposes (e.g. "system.indexes")

        NamespaceString( const char * ns ) { init(ns); }
        NamespaceString( const string& ns ) { init(ns.c_str()); }
        string ns() const { return db + '.' + coll; }
        bool isSystem() const { return strncmp(coll.c_str(), "system.", 7) == 0; }
    private:
        void init(const char *ns) {
            const char *p = strchr(ns, '.');
            if( p == 0 ) return;
            db = string(ns, p - ns);
            coll = p + 1;
        }
    };

#pragma pack(1)
    /* This helper class is used to make the HashMap below in NamespaceDetails e.g. see line:
          HashTable<Namespace,NamespaceDetails> *ht;
    */
    class Namespace {
    public:
        explicit Namespace(const char *ns) { *this = ns; }
        Namespace& operator=(const char *ns);

        bool hasDollarSign() const { return strchr( buf , '$' ) > 0;  }
        void kill() { buf[0] = 0x7f; }
        bool operator==(const char *r) const { return strcmp(buf, r) == 0; }
        bool operator==(const Namespace& r) const { return strcmp(buf, r.buf) == 0; }
        int hash() const; // value returned is always > 0
        string toString() const { return (string) buf; }
        operator string() const { return (string) buf; }

        /* NamespaceDetails::Extra was added after fact to allow chaining of data blocks to support more than 10 indexes
           (more than 10 IndexDetails).  It's a bit hacky because of this late addition with backward
           file support. */
        string extraName(int i) const;
        bool isExtra() const; /* ends with $extr... -- when true an extra block not a normal NamespaceDetails block */

        string getSisterNS( const char * local ) const;

        enum MaxNsLenValue { MaxNsLen = 128 };
    private:
        char buf[MaxNsLen];
    };
#pragma pack()

} // namespace mongo

#include "index.h"

namespace mongo {

    bool legalClientSystemNS( const string& ns , bool write );

    /* deleted lists -- linked lists of deleted records -- are placed in 'buckets' of various sizes
       so you can look for a deleterecord about the right size.
    */
    const int Buckets = 19;
    const int MaxBucket = 18;

    extern int bucketSizes[];

#pragma pack(1)
    /* NamespaceDetails : this is the "header" for a collection that has all its details.
       It's in the .ns file and this is a memory mapped region (thus the pack pragma above).
    */
    class NamespaceDetails {
    public:
        enum { NIndexesMax = 64, NIndexesExtra = 30, NIndexesBase  = 10 };

        /*-------- data fields, as present on disk : */
        DiskLoc firstExtent;
        DiskLoc lastExtent;
        /* NOTE: capped collections v1 override the meaning of deletedList.
                 deletedList[0] points to a list of free records (DeletedRecord's) for all extents in
                 the capped namespace.
                 deletedList[1] points to the last record in the prev extent.  When the "current extent"
                 changes, this value is updated.  !deletedList[1].isValid() when this value is not
                 yet computed.
        */
        DiskLoc deletedList[Buckets];
        // ofs 168 (8 byte aligned)
        struct Stats {
            // datasize and nrecords MUST Be adjacent code assumes!
            long long datasize; // this includes padding, but not record headers
            long long nrecords;
        } stats;
        int lastExtentSize;
        int nIndexes;
    private:
        // ofs 192
        IndexDetails _indexes[NIndexesBase];
    public:
        // ofs 352 (16 byte aligned)
        int capped;
        int max;                              // max # of objects for a capped table.  TODO: should this be 64 bit?
        double paddingFactor;                 // 1.0 = no padding.
        // ofs 386 (16)
        int flags;
        DiskLoc capExtent;
        DiskLoc capFirstNewRecord;
        unsigned short dataFileVersion;       // NamespaceDetails version.  So we can do backward compatibility in the future. See filever.h
        unsigned short indexFileVersion;
        unsigned long long multiKeyIndexBits;
    private:
        // ofs 400 (16)
        unsigned long long reservedA;
        long long extraOffset;                // where the $extra info is located (bytes relative to this)
    public:
        int indexBuildInProgress;   // 1 if in prog
        unsigned reservedB;
        // ofs 424 (8)
        struct Capped2 {
            unsigned long long cc2_ptr;       // see capped.cpp
            unsigned fileNumber;
        } capped2;
        char reserved[60];
        /*-------- end data 496 bytes */

        explicit NamespaceDetails( const DiskLoc &loc, bool _capped );

        class Extra {
            long long _next;
        public:
            IndexDetails details[NIndexesExtra];
        private:
            unsigned reserved2;
            unsigned reserved3;
            Extra(const Extra&) { assert(false); }
            Extra& operator=(const Extra& r) { assert(false); return *this; }
        public:
            Extra() { }
            long ofsFrom(NamespaceDetails *d) {
                return ((char *) this) - ((char *) d);
            }
            void init() { memset(this, 0, sizeof(Extra)); }
            Extra* next(NamespaceDetails *d) {
                if( _next == 0 ) return 0;
                return (Extra*) (((char *) d) + _next);
            }
            void setNext(long ofs) { *getDur().writing(&_next) = ofs;  }
            void copy(NamespaceDetails *d, const Extra& e) {
                memcpy(this, &e, sizeof(Extra));
                _next = 0;
            }
        };
        Extra* extra() {
            if( extraOffset == 0 ) return 0;
            return (Extra *) (((char *) this) + extraOffset);
        }
        /* add extra space for indexes when more than 10 */
        Extra* allocExtra(const char *ns, int nindexessofar);
        void copyingFrom(const char *thisns, NamespaceDetails *src); // must be called when renaming a NS to fix up extra

        /* called when loaded from disk */
        void onLoad(const Namespace& k);

        /* dump info on this namespace.  for debugging. */
        void dump(const Namespace& k);

        /* dump info on all extents for this namespace.  for debugging. */
        void dumpExtents();

    private:
        Extent *theCapExtent() const { return capExtent.ext(); }
        void advanceCapExtent( const char *ns );
        DiskLoc __capAlloc(int len);
        DiskLoc cappedAlloc(const char *ns, int len);
        DiskLoc &cappedFirstDeletedInCurExtent();
        bool nextIsInCapExtent( const DiskLoc &dl ) const;

    public:
        DiskLoc& cappedListOfAllDeletedRecords() { return deletedList[0]; }
        DiskLoc& cappedLastDelRecLastExtent()    { return deletedList[1]; }
        void cappedDumpDelInfo();
        bool capLooped() const { return capped && capFirstNewRecord.isValid();  }
        bool inCapExtent( const DiskLoc &dl ) const;
        void cappedCheckMigrate();
        void cappedTruncateAfter(const char *ns, DiskLoc end, bool inclusive);
        void emptyCappedCollection(const char *ns);

        /* when a background index build is in progress, we don't count the index in nIndexes until
           complete, yet need to still use it in _indexRecord() - thus we use this function for that.
        */
        int nIndexesBeingBuilt() const { return nIndexes + indexBuildInProgress; }

        /* NOTE: be careful with flags.  are we manipulating them in read locks?  if so,
                 this isn't thread safe.  TODO
        */
        enum NamespaceFlags {
            Flag_HaveIdIndex = 1 << 0 // set when we have _id index (ONLY if ensureIdIndex was called -- 0 if that has never been called)
        };

        IndexDetails& idx(int idxNo, bool missingExpected = false );

        IndexDetails& inProgIdx() {
            DEV assert(indexBuildInProgress);
            return idx(nIndexes);
        }

        class IndexIterator {
        public:
            int pos() { return i; } // note this is the next one to come
            bool more() { return i < n; }
            IndexDetails& next() { return d->idx(i++); }
        private:
            friend class NamespaceDetails;
            int i, n;
            NamespaceDetails *d;
            IndexIterator(NamespaceDetails *_d);
        };

        IndexIterator ii() { return IndexIterator(this); }

        /* hackish - find our index # in the indexes array */
        int idxNo(IndexDetails& idx);

        /* multikey indexes are indexes where there are more than one key in the index
             for a single document. see multikey in wiki.
           for these, we have to do some dedup work on queries.
        */
        bool isMultikey(int i) const { return (multiKeyIndexBits & (((unsigned long long) 1) << i)) != 0; }
        void setIndexIsMultikey(int i) {
            dassert( i < NIndexesMax );
            unsigned long long x = ((unsigned long long) 1) << i;
            if( multiKeyIndexBits & x ) return;
            *getDur().writing(&multiKeyIndexBits) |= x;
        }
        void clearIndexIsMultikey(int i) {
            dassert( i < NIndexesMax );
            unsigned long long x = ((unsigned long long) 1) << i;
            if( (multiKeyIndexBits & x) == 0 ) return;
            *getDur().writing(&multiKeyIndexBits) &= ~x;
        }

        /* add a new index.  does not add to system.indexes etc. - just to NamespaceDetails.
           caller must populate returned object.
         */
        IndexDetails& addIndex(const char *thisns, bool resetTransient=true);

        void aboutToDeleteAnIndex() { 
            *getDur().writing(&flags) = flags & ~Flag_HaveIdIndex;
        }

        /* returns index of the first index in which the field is present. -1 if not present. */
        int fieldIsIndexed(const char *fieldName);

        void paddingFits() {
            double x = paddingFactor - 0.01;
            if ( x >= 1.0 )
                getDur().setNoJournal(&paddingFactor, &x, sizeof(x));
        }
        void paddingTooSmall() {
            double x = paddingFactor + 0.6;
            if ( x <= 2.0 )
                getDur().setNoJournal(&paddingFactor, &x, sizeof(x));
        }

        // @return offset in indexes[]
        int findIndexByName(const char *name);

        // @return offset in indexes[]
        int findIndexByKeyPattern(const BSONObj& keyPattern);

        void findIndexByType( const string& name , vector<int>& matches ) {
            IndexIterator i = ii();
            while ( i.more() ) {
                if ( i.next().getSpec().getTypeName() == name )
                    matches.push_back( i.pos() - 1 );
            }
        }

        /* @return -1 = not found
           generally id is first index, so not that expensive an operation (assuming present).
        */
        int findIdIndex() {
            IndexIterator i = ii();
            while( i.more() ) {
                if( i.next().isIdIndex() )
                    return i.pos()-1;
            }
            return -1;
        }

        /* return which "deleted bucket" for this size object */
        static int bucket(int n) {
            for ( int i = 0; i < Buckets; i++ )
                if ( bucketSizes[i] > n )
                    return i;
            return Buckets-1;
        }

        /* allocate a new record.  lenToAlloc includes headers. */
        DiskLoc alloc(const char *ns, int lenToAlloc, DiskLoc& extentLoc);
        /* add a given record to the deleted chains for this NS */
        void addDeletedRec(DeletedRecord *d, DiskLoc dloc);
        void dumpDeleted(set<DiskLoc> *extents = 0);
        // Start from firstExtent by default.
        DiskLoc firstRecord( const DiskLoc &startExtent = DiskLoc() ) const;
        // Start from lastExtent by default.
        DiskLoc lastRecord( const DiskLoc &startExtent = DiskLoc() ) const;
        long long storageSize( int * numExtents = 0 , BSONArrayBuilder * extentInfo = 0 ) const;

        int averageObjectSize() {
            if ( stats.nrecords == 0 )
                return 5;
            return (int) (stats.datasize / stats.nrecords);
        }

        NamespaceDetails *writingWithoutExtra() {
            return ( NamespaceDetails* ) getDur().writingPtr( this, sizeof( NamespaceDetails ) );
        }
        NamespaceDetails *writingWithExtra();

    private:
        DiskLoc _alloc(const char *ns, int len);
        void maybeComplain( const char *ns, int len ) const;
        DiskLoc __stdAlloc(int len);
        void compact(); // combine adjacent deleted records
        friend class NamespaceIndex;
        struct ExtraOld {
            // note we could use this field for more chaining later, so don't waste it:
            unsigned long long reserved1;
            IndexDetails details[NIndexesExtra];
            unsigned reserved2;
            unsigned reserved3;
        };
        void cappedTruncateLastDelUpdate();
        BOOST_STATIC_ASSERT( NIndexesMax <= NIndexesBase + NIndexesExtra*2 );
        BOOST_STATIC_ASSERT( NIndexesMax <= 64 ); // multiKey bits
        BOOST_STATIC_ASSERT( sizeof(NamespaceDetails::ExtraOld) == 496 );
        BOOST_STATIC_ASSERT( sizeof(NamespaceDetails::Extra) == 496 );
    }; // NamespaceDetails
#pragma pack()

    /* NamespaceDetailsTransient

       these are things we know / compute about a namespace that are transient -- things
       we don't actually store in the .ns file.  so mainly caching of frequently used
       information.

       CAUTION: Are you maintaining this properly on a collection drop()?  A dropdatabase()?  Be careful.
                The current field "allIndexKeys" may have too many keys in it on such an occurrence;
                as currently used that does not cause anything terrible to happen.

       todo: cleanup code, need abstractions and separation
    */
    class NamespaceDetailsTransient : boost::noncopyable {
        BOOST_STATIC_ASSERT( sizeof(NamespaceDetails) == 496 );

        /* general ------------------------------------------------------------- */
    private:
        string _ns;
        void reset();
        static std::map< string, shared_ptr< NamespaceDetailsTransient > > _map;
    public:
        NamespaceDetailsTransient(const char *ns) : _ns(ns), _keysComputed(false), _qcWriteCount() { }
        /* _get() is not threadsafe -- see get_inlock() comments */
        static NamespaceDetailsTransient& _get(const char *ns);
        /* use get_w() when doing write operations */
        static NamespaceDetailsTransient& get_w(const char *ns) {
            DEV assertInWriteLock();
            return _get(ns);
        }
        void addedIndex() { reset(); }
        void deletedIndex() { reset(); }
        /* Drop cached information on all namespaces beginning with the specified prefix.
           Can be useful as index namespaces share the same start as the regular collection.
           SLOW - sequential scan of all NamespaceDetailsTransient objects */
        static void clearForPrefix(const char *prefix);

        /* indexKeys() cache ---------------------------------------------------- */
        /* assumed to be in write lock for this */
    private:
        bool _keysComputed;
        set<string> _indexKeys;
        void computeIndexKeys();
    public:
        /* get set of index keys for this namespace.  handy to quickly check if a given
           field is indexed (Note it might be a secondary component of a compound index.)
        */
        set<string>& indexKeys() {
            DEV assertInWriteLock();
            if ( !_keysComputed )
                computeIndexKeys();
            return _indexKeys;
        }

        /* IndexSpec caching */
    private:
        map<const IndexDetails*,IndexSpec> _indexSpecs;
        static mongo::mutex _isMutex;
    public:
        const IndexSpec& getIndexSpec( const IndexDetails * details ) {
            IndexSpec& spec = _indexSpecs[details];
            if ( ! spec._finishedInit ) {
                scoped_lock lk(_isMutex);
                if ( ! spec._finishedInit ) {
                    spec.reset( details );
                    assert( spec._finishedInit );
                }
            }
            return spec;
        }

        /* query cache (for query optimizer) ------------------------------------- */
    private:
        int _qcWriteCount;
        map< QueryPattern, pair< BSONObj, long long > > _qcCache;
    public:
        static mongo::mutex _qcMutex;
        /* you must be in the qcMutex when calling this (and using the returned val): */
        static NamespaceDetailsTransient& get_inlock(const char *ns) {
            return _get(ns);
        }
        void clearQueryCache() { // public for unit tests
            _qcCache.clear();
            _qcWriteCount = 0;
        }
        /* you must notify the cache if you are doing writes, as query plan optimality will change */
        void notifyOfWriteOp() {
            if ( _qcCache.empty() )
                return;
            if ( ++_qcWriteCount >= 100 )
                clearQueryCache();
        }
        BSONObj indexForPattern( const QueryPattern &pattern ) {
            return _qcCache[ pattern ].first;
        }
        long long nScannedForPattern( const QueryPattern &pattern ) {
            return _qcCache[ pattern ].second;
        }
        void registerIndexForPattern( const QueryPattern &pattern, const BSONObj &indexKey, long long nScanned ) {
            _qcCache[ pattern ] = make_pair( indexKey, nScanned );
        }

    }; /* NamespaceDetailsTransient */

    inline NamespaceDetailsTransient& NamespaceDetailsTransient::_get(const char *ns) {
        shared_ptr< NamespaceDetailsTransient > &t = _map[ ns ];
        if ( t.get() == 0 )
            t.reset( new NamespaceDetailsTransient(ns) );
        return *t;
    }

    /* NamespaceIndex is the ".ns" file you see in the data directory.  It is the "system catalog"
       if you will: at least the core parts.  (Additional info in system.* collections.)
    */
    class NamespaceIndex {
        friend class NamespaceCursor;

    public:
        NamespaceIndex(const string &dir, const string &database) :
            ht( 0 ), dir_( dir ), database_( database ) {}

        /* returns true if new db will be created if we init lazily */
        bool exists() const;

        void init();

        void add_ns(const char *ns, DiskLoc& loc, bool capped) {
            NamespaceDetails details( loc, capped );
            add_ns( ns, details );
        }
        void add_ns( const char *ns, const NamespaceDetails &details ) {
            init();
            Namespace n(ns);
            uassert( 10081 , "too many namespaces/collections", ht->put(n, details));
        }

        /* just for diagnostics */
        /*size_t detailsOffset(NamespaceDetails *d) {
            if ( !ht )
                return -1;
            return ((char *) d) -  (char *) ht->nodes;
        }*/

        NamespaceDetails* details(const char *ns) {
            if ( !ht )
                return 0;
            Namespace n(ns);
            NamespaceDetails *d = ht->get(n);
            if ( d && d->capped )
                d->cappedCheckMigrate();
            return d;
        }

        void kill_ns(const char *ns);

        bool find(const char *ns, DiskLoc& loc) {
            NamespaceDetails *l = details(ns);
            if ( l ) {
                loc = l->firstExtent;
                return true;
            }
            return false;
        }

        bool allocated() const {
            return ht != 0;
        }

        void getNamespaces( list<string>& tofill , bool onlyCollections = true ) const;

        NamespaceDetails::Extra* newExtra(const char *ns, int n, NamespaceDetails *d);

        boost::filesystem::path path() const;

    private:
        void maybeMkdir() const;

        MongoMMF f;
        HashTable<Namespace,NamespaceDetails> *ht;
        string dir_;
        string database_;
    };

    extern string dbpath; // --dbpath parm
    extern bool directoryperdb;

    // Rename a namespace within current 'client' db.
    // (Arguments should include db name)
    void renameNamespace( const char *from, const char *to );

    // "database.a.b.c" -> "database"
    inline void nsToDatabase(const char *ns, char *database) {
        const char *p = ns;
        char *q = database;
        while ( *p != '.' ) {
            if ( *p == 0 )
                break;
            *q++ = *p++;
        }
        *q = 0;
        if (q-database>=MaxDatabaseNameLen) {
            log() << "nsToDatabase: ns too long. terminating, buf overrun condition" << endl;
            dbexit( EXIT_POSSIBLE_CORRUPTION );
        }
    }
    inline string nsToDatabase(const char *ns) {
        char buf[MaxDatabaseNameLen];
        nsToDatabase(ns, buf);
        return buf;
    }
    inline string nsToDatabase(const string& ns) {
        size_t i = ns.find( '.' );
        if ( i == string::npos )
            return ns;
        return ns.substr( 0 , i );
    }

} // namespace mongo

---

mongodb
Author(s): Nate Koenig
autogenerated on Fri Jan 11 12:15:18 2013