关于mongodb的db.stats()

关于mongodb的db.stats() 的解释：

其中：
collections：集合的个数
objects: 对象的个数，循环每个集合得到的，每个集合的记录数（nrecords）之和
avgObjSize：平均每个对象的大小，通过 dataSize / objects 得到
dataSize：每个集合的dataSize之和
storageSize: 每个集合的storageSize之和
fileSize： db下面的物理存储文件的大小；物理存储文件比实际的数据要大一些，这是是mongo的预分配机制

这里最难理解的大概就是 storageSize了，它和dataSize的差异参看： http://blog.nosqlfan.com/html/2654.html

相关代码db\dbcommands.cpp：

bool run(const string& dbname, BSONObj& jsobj, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {
    list<string> collections;
    Database* d = cc().database();
    if ( d )
        d->namespaceIndex.getNamespaces( collections );
    longlong ncollections = 0;
    longlong objects = 0;
    longlong size = 0;
    longlong storageSize = 0;
    longlong numExtents = 0;
    longlong indexes = 0;
    longlong indexSize = 0;
    for (list<string>::const_iterator it = collections.begin(); it != collections.end(); ++it) {
        const string ns = *it;
        NamespaceDetails * nsd = nsdetails( ns.c_str() );
        if ( ! nsd ) {
            errmsg = "missing ns: ";
            errmsg += ns;
            returnfalse;
        }
        ncollections += 1;
        objects += nsd->stats.nrecords;
        size += nsd->stats.datasize;
        int temp;
        storageSize += nsd->storageSize( &temp );
        numExtents += temp;
        indexes += nsd->nIndexes;
        indexSize += getIndexSizeForCollection(dbname, ns);
    }

    result.append      ( "db" , dbname );
    result.appendNumber( "collections" , ncollections );
    result.appendNumber( "objects" , objects );
    result.append      ( "avgObjSize" , objects == 0 ? 0 : double(size) / double(objects) );
    result.appendNumber( "dataSize" , size );
    result.appendNumber( "storageSize" , storageSize);
    result.appendNumber( "numExtents" , numExtents );
    result.appendNumber( "indexes" , indexes );
    result.appendNumber( "indexSize" , indexSize );
    result.appendNumber( "fileSize" , d->fileSize() );
    returntrue;
}
dDBStats;

bool run(const string& dbname, BSONObj& jsobj, string& errmsg, BSONObjBuilder& result, bool fromRepl ) {

list<string> collections;

Database* d = cc().database();

if ( d )

d->namespaceIndex.getNamespaces( collections );

longlong ncollections = 0;

longlong objects = 0;

longlong size = 0;

longlong storageSize = 0;

longlong numExtents = 0;

longlong indexes = 0;

longlong indexSize = 0;

for (list<string>::const_iterator it = collections.begin(); it != collections.end(); ++it) {

const string ns = *it;

NamespaceDetails * nsd = nsdetails( ns.c_str() );

if ( ! nsd ) {

errmsg = "missing ns: ";

errmsg += ns;

returnfalse;

}

ncollections += 1;

objects += nsd->stats.nrecords;

size += nsd->stats.datasize;

int temp;

storageSize += nsd->storageSize( &temp );

numExtents += temp;

indexes += nsd->nIndexes;

indexSize += getIndexSizeForCollection(dbname, ns);

}

result.append ( "db" , dbname );

result.appendNumber( "collections" , ncollections );

result.appendNumber( "objects" , objects );

result.append ( "avgObjSize" , objects == 0 ? 0 : double(size) / double(objects) );

result.appendNumber( "dataSize" , size );

result.appendNumber( "storageSize" , storageSize);

result.appendNumber( "numExtents" , numExtents );

result.appendNumber( "indexes" , indexes );

result.appendNumber( "indexSize" , indexSize );

result.appendNumber( "fileSize" , d->fileSize() );

returntrue;

}

dDBStats;

longlong Database::fileSize() const {
    longlong size=0;
    for (int n=0; exists(n); n++)
        size += boost::filesystem::file_size( fileName(n) );
    return size;
}

longlong Database::fileSize() const {

longlong size=0;

for (int n=0; exists(n); n++)

size += boost::filesystem::file_size( fileName(n) );

return size;

}

        bool run(const string&amp; dbname, BSONObj&amp; jsobj, string&amp; errmsg, BSONObjBuilder&amp; result, bool fromRepl ) {             list&lt;string&gt; collections;             Database* d = cc().database();             if ( d )                 d-&gt;namespaceIndex.getNamespaces( collections );              long long ncollections = 0;             long long objects = 0;             long long size = 0;             long long storageSize = 0;             long long numExtents = 0;             long long indexes = 0;             long long indexSize = 0;              for (list&lt;string&gt;::const_iterator it = collections.begin(); it != collections.end(); ++it) {                 const string ns = *it;                  NamespaceDetails * nsd = nsdetails( ns.c_str() );                 if ( ! nsd ) {                     errmsg = "missing ns: ";                     errmsg += ns;                     return false;                 }                  ncollections += 1;                 objects += nsd-&gt;stats.nrecords;                 size += nsd-&gt;stats.datasize;                  int temp;                 storageSize += nsd-&gt;storageSize( &amp;temp );                 numExtents += temp;                  indexes += nsd-&gt;nIndexes;                 indexSize += getIndexSizeForCollection(dbname, ns);             }                          result.append      ( "db" , dbname );             result.appendNumber( "collections" , ncollections );             result.appendNumber( "objects" , objects );             result.append      ( "avgObjSize" , objects == 0 ? 0 : double(size) / double(objects) );             result.appendNumber( "dataSize" , size );             result.appendNumber( "storageSize" , storageSize);             result.appendNumber( "numExtents" , numExtents );             result.appendNumber( "indexes" , indexes );             result.appendNumber( "indexSize" , indexSize );             result.appendNumber( "fileSize" , d-&gt;fileSize() );              return true;         }     } cmdDBStats;

bool run(const string& dbname, BSONObj& jsobj, string& errmsg, BSONObjBuilder& result, bool fromRepl ) { list<string> collections; Database* d = cc().database(); if ( d ) d->namespaceIndex.getNamespaces( collections ); long long ncollections = 0; long long objects = 0; long long size = 0; long long storageSize = 0; long long numExtents = 0; long long indexes = 0; long long indexSize = 0; for (list<string>::const_iterator it = collections.begin(); it != collections.end(); ++it) { const string ns = *it; NamespaceDetails * nsd = nsdetails( ns.c_str() ); if ( ! nsd ) { errmsg = "missing ns: "; errmsg += ns; return false; } ncollections += 1; objects += nsd->stats.nrecords; size += nsd->stats.datasize; int temp; storageSize += nsd->storageSize( &temp ); numExtents += temp; indexes += nsd->nIndexes; indexSize += getIndexSizeForCollection(dbname, ns); } result.append ( "db" , dbname ); result.appendNumber( "collections" , ncollections ); result.appendNumber( "objects" , objects ); result.append ( "avgObjSize" , objects == 0 ? 0 : double(size) / double(objects) ); result.appendNumber( "dataSize" , size ); result.appendNumber( "storageSize" , storageSize); result.appendNumber( "numExtents" , numExtents ); result.appendNumber( "indexes" , indexes ); result.appendNumber( "indexSize" , indexSize ); result.appendNumber( "fileSize" , d->fileSize() ); return true; } } cmdDBStats;

boost::filesystem::path Database::fileName( int n ) const {
    stringstream ss;
    ss << name << '.' << n;
    boost::filesystem::path fullName;
    fullName = boost::filesystem::path(path);
    if ( directoryperdb )
        fullName /= name;
    fullName /= ss.str();
    return fullName;
}

boost::filesystem::path Database::fileName( int n ) const {

stringstream ss;

ss << name << '.' << n;

boost::filesystem::path fullName;

fullName = boost::filesystem::path(path);

if ( directoryperdb )

fullName /= name;

fullName /= ss.str();

return fullName;

}

关于mongodb的db.stats()

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