path: root/db/namespace.h

// namespace.h

/**
*    Copyright (C) 2008 10gen 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/>.
*/

#pragma once

#include "../stdafx.h"

#include "jsobj.h"
#include "storage.h"

#include "../util/hashtab.h"
#include "../util/mmap.h"

namespace mongo {

    class Cursor;

#pragma pack(1)

// "database.a.b.c" -> "database"
    const int MaxClientLen = 256;
    inline void nsToClient(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>=MaxClientLen) {
            problem() << "nsToClient: ns too long. terminating, buf overrun condition" << endl;
            dbexit(60);
        }
    }
    inline string nsToClient(const char *ns) {
        char buf[MaxClientLen];
        nsToClient(ns, buf);
        return buf;
    }

    class NamespaceString {
    public:
        string db;
        string coll;
    private:
        void init(const char *ns) { 
            const char *p = strchr(ns, '.');
            if( p == 0 ) return;
            db = string(ns, p - ns);
            coll = p + 1;
        }
    public:
        NamespaceString( const char * ns ) { init(ns); }
        NamespaceString( const string& ns ) { init(ns.c_str()); }
    };

    class Namespace {
    public:
        enum { MaxNsLen = 128 };
        Namespace(const char *ns) {
            *this = ns;
        }
        Namespace& operator=(const char *ns) {
            memset(buf, 0, MaxNsLen); /* this is just to keep stuff clean in the files for easy dumping and reading */
            strcpy_s(buf, MaxNsLen, ns);
            return *this;
        }

        void kill() {
            buf[0] = 0x7f;
        }

        bool operator==(const char *r) {
            return strcmp(buf, r) == 0;
        }
        bool operator==(const Namespace& r) {
            return strcmp(buf, r.buf) == 0;
        }
        int hash() const {
            unsigned x = 0;
            const char *p = buf;
            while ( *p ) {
                x = x * 131 + *p;
                p++;
            }
            return (x & 0x7fffffff) | 0x8000000; // must be > 0
        }


        /**
           ( foo.bar ).getSisterNS( "blah" ) == foo.blah
         */
        string getSisterNS( const char * local ) {
            assert( local && local[0] != '.' );
            string old(buf);
            if ( old.find( "." ) != string::npos )
                old = old.substr( 0 , old.find( "." ) );
            return old + "." + local;
        }

        char buf[MaxNsLen];
    };

    const int Buckets = 19;
    const int MaxBucket = 18;
    const int MaxIndexes = 10;

    //extern BSONObj idKeyPattern; // { _id : 1 } 

    class IndexDetails {
    public:
        DiskLoc head; /* btree head */

        /* Location of index info object. Format:

             { name:"nameofindex", ns:"parentnsname", key: {keypattobject} }

           This object is in the system.indexes collection.  Note that since we
           have a pointer to the object here, the object in system.indexes must
           never move.
        */
        DiskLoc info;

        /* extract key value from the query object
           e.g., if key() == { x : 1 },
                 { x : 70, y : 3 } -> { x : 70 }
           handles our embedded dot notation too.
        */
        BSONObj getKeyFromQuery(const BSONObj& query) {
            BSONObj k = keyPattern();
            BSONObj res = query.extractFieldsUnDotted(k);
            assert(res.objsize() != 0); // guard against a seg fault if details is 0
            return res;
        }

        /* pull out the relevant key objects from obj, so we
           can index them.  Note that the set is multiple elements
           only when it's a "multikey" array.
           keys will be left empty if key not found in the object.
        */
        void getKeysFromObject( const BSONObj& obj, BSONObjSetDefaultOrder& keys) const;

        /* get the key pattern for this object.
           e.g., { lastname:1, firstname:1 }
        */
        BSONObj keyPattern() const {
            return info.obj().getObjectField("key");
        }

        // returns name of this index's storage area
        // database.table.$index
        string indexNamespace() {
            BSONObj io = info.obj();
            string s;
            s.reserve(Namespace::MaxNsLen);
            s = io.getStringField("ns");
            assert( !s.empty() );
            s += ".$";
            s += io.getStringField("name");
            return s;
        }

        string indexName() const { // e.g. "ts_1"
            BSONObj io = info.obj();
            return io.getStringField("name");
        }

        /* returns true if this is the _id index. */
        bool isIdIndex() const { 
            BSONObjIterator i(keyPattern());
            BSONElement e = i.next();
            if( strcmp(e.fieldName(), "_id") != 0 ) return false;
            return i.next().eoo();
        }

        /* gets not our namespace name (indexNamespace for that),
           but the collection we index, its name.
           */
        string parentNS() const {
            BSONObj io = info.obj();
            return io.getStringField("ns");
        }

        /* delete this index.  does NOT celan up the system catalog
           (system.indexes or system.namespaces) -- only NamespaceIndex.
        */
        void kill();
    };

    extern int bucketSizes[];

    /* this is the "header" for a collection that has all its details.  in the .ns file.
    */
    class NamespaceDetails {
    public:
        NamespaceDetails( const DiskLoc &loc, bool _capped ) {
            /* be sure to initialize new fields here -- doesn't default to zeroes the way we use it */
            firstExtent = lastExtent = capExtent = loc;
            datasize = nrecords = 0;
            lastExtentSize = 0;
            nIndexes = 0;
            capped = _capped;
            max = 0x7fffffff;
            paddingFactor = 1.0;
            flags = 0;
            capFirstNewRecord = DiskLoc();
            // Signal that we are on first allocation iteration through extents.
            capFirstNewRecord.setInvalid();
            // For capped case, signal that we are doing initial extent allocation.
            if ( capped )
                deletedList[ 1 ].setInvalid();
            memset(reserved, 0, sizeof(reserved));
        }
        DiskLoc firstExtent;
        DiskLoc lastExtent;
        DiskLoc deletedList[Buckets];
        long long datasize;
        long long nrecords;
        int lastExtentSize;
        int nIndexes;
        IndexDetails indexes[MaxIndexes];
        int capped;
        int max; // max # of objects for a capped table.
        double paddingFactor; // 1.0 = no padding.
        int flags;
        DiskLoc capExtent;
        DiskLoc capFirstNewRecord;
        char reserved[108];

        enum {
            Flag_HaveIdIndex = 1 // set when we have _id index (ONLY if ensureIdIndex was called -- 0 if that has never been called)
        };

        /* you MUST call when adding an index.  see pdfile.cpp */
        void addingIndex(const char *thisns, IndexDetails& details);

        void aboutToDeleteAnIndex() {
            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 )
                paddingFactor = x;
        }
        void paddingTooSmall() {
            double x = paddingFactor + 0.6;
            if ( x <= 2.0 )
                paddingFactor = x;
        }

        //returns offset in indexes[]
        int findIndexByName(const char *name) {
            for ( int i = 0; i < nIndexes; i++ ) {
                if ( strcmp(indexes[i].info.obj().getStringField("name"),name) == 0 )
                    return i;
            }
            return -1;
        }

        int findIdIndex() {
            for( int i = 0; i < nIndexes; i++ ) {
                if( indexes[i].isIdIndex() )
                    return i;
            }
            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);

        bool capLooped() const {
            return capped && capFirstNewRecord.isValid();
        }

        // Start from firstExtent by default.
        DiskLoc firstRecord( const DiskLoc &startExtent = DiskLoc() ) const;

        // Start from lastExtent by default.
        DiskLoc lastRecord( const DiskLoc &startExtent = DiskLoc() ) const;

        bool inCapExtent( const DiskLoc &dl ) const;

        void checkMigrate();

    private:
        Extent *theCapExtent() const {
            return capExtent.ext();
        }
        void advanceCapExtent( const char *ns );
        void maybeComplain( const char *ns, int len ) const;
        DiskLoc __stdAlloc(int len);
        DiskLoc __capAlloc(int len);
        DiskLoc _alloc(const char *ns, int len);
        void compact();

        DiskLoc &firstDeletedInCapExtent();
        bool nextIsInCapExtent( const DiskLoc &dl ) const;
    };

#pragma pack()

    /* 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.
    */
    class NamespaceDetailsTransient : boost::noncopyable {
        string ns;
        bool haveIndexKeys;
        set<string> allIndexKeys;
        void computeIndexKeys();
    public:
        NamespaceDetailsTransient(const char *_ns) : ns(_ns) {
            haveIndexKeys=false; /*lazy load them*/
        }

        /* get set of index keys for this namespace.  handy to quickly check if a given
           field is indexed (Note it might be a seconary component of a compound index.)
        */
        set<string>& indexKeys() {
            if ( !haveIndexKeys ) {
                haveIndexKeys=true;
                computeIndexKeys();
            }
            return allIndexKeys;
        }

        void addedIndex() {
            haveIndexKeys=false;
        }
        void deletedIndex() {
            haveIndexKeys = false;
        }
    private:
        static std::map<string,NamespaceDetailsTransient*> map;
    public:
        static NamespaceDetailsTransient& get(const char *ns);
    };

    /* 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(const char *ns, DiskLoc& loc, bool capped) {
            init();
            Namespace n(ns);
            NamespaceDetails details( loc, capped );
            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->checkMigrate();
            return d;
        }

        void kill(const char *ns) {
            if ( !ht )
                return;
            Namespace n(ns);
            ht->kill(n);
        }

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

    private:
        boost::filesystem::path path() const;
        
        MemoryMappedFile f;
        HashTable<Namespace,NamespaceDetails> *ht;
        string dir_;
        string database_;
    };

    extern const char *dbpath;

} // namespace mongo