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// d_split.cpp
/**
* 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/>.
*/
#include "pch.h"
#include <map>
#include <string>
#include "../db/btree.h"
#include "../db/commands.h"
#include "../db/dbmessage.h"
#include "../db/jsobj.h"
#include "../db/query.h"
#include "../db/queryoptimizer.h"
namespace mongo {
// TODO: Fold these checks into each command.
static IndexDetails *cmdIndexDetailsForRange( const char *ns, string &errmsg, BSONObj &min, BSONObj &max, BSONObj &keyPattern ) {
if ( ns[ 0 ] == '\0' || min.isEmpty() || max.isEmpty() ) {
errmsg = "invalid command syntax (note: min and max are required)";
return 0;
}
return indexDetailsForRange( ns, errmsg, min, max, keyPattern );
}
class CmdMedianKey : public Command {
public:
CmdMedianKey() : Command( "medianKey" ) {}
virtual bool slaveOk() const { return true; }
virtual LockType locktype() const { return READ; }
virtual void help( stringstream &help ) const {
help <<
"Internal command.\n"
"example: { medianKey:\"blog.posts\", keyPattern:{x:1}, min:{x:10}, max:{x:55} }\n"
"NOTE: This command may take a while to run";
}
bool run(const string& dbname, BSONObj& jsobj, string& errmsg, BSONObjBuilder& result, bool fromRepl ){
const char *ns = jsobj.getStringField( "medianKey" );
BSONObj min = jsobj.getObjectField( "min" );
BSONObj max = jsobj.getObjectField( "max" );
BSONObj keyPattern = jsobj.getObjectField( "keyPattern" );
Client::Context ctx( ns );
IndexDetails *id = cmdIndexDetailsForRange( ns, errmsg, min, max, keyPattern );
if ( id == 0 )
return false;
Timer timer;
int num = 0;
NamespaceDetails *d = nsdetails(ns);
int idxNo = d->idxNo(*id);
// only yielding on firt half for now
// after this it should be in ram, so 2nd should be fast
{
shared_ptr<Cursor> c( new BtreeCursor( d, idxNo, *id, min, max, false, 1 ) );
scoped_ptr<ClientCursor> cc( new ClientCursor( QueryOption_NoCursorTimeout , c , ns ) );
while ( c->ok() ){
num++;
c->advance();
if ( ! cc->yieldSometimes() )
break;
}
}
num /= 2;
BtreeCursor c( d, idxNo, *id, min, max, false, 1 );
for( ; num; c.advance(), --num );
ostringstream os;
os << "Finding median for index: " << keyPattern << " between " << min << " and " << max;
logIfSlow( timer , os.str() );
if ( !c.ok() ) {
errmsg = "no index entries in the specified range";
return false;
}
BSONObj median = c.prettyKey( c.currKey() );
result.append( "median", median );
int x = median.woCompare( min , BSONObj() , false );
int y = median.woCompare( max , BSONObj() , false );
if ( x == 0 || y == 0 ){
// its on an edge, ok
}
else if ( x < 0 && y < 0 ){
log( LL_ERROR ) << "median error (1) min: " << min << " max: " << max << " median: " << median << endl;
errmsg = "median error 1";
return false;
}
else if ( x > 0 && y > 0 ){
log( LL_ERROR ) << "median error (2) min: " << min << " max: " << max << " median: " << median << endl;
errmsg = "median error 2";
return false;
}
return true;
}
} cmdMedianKey;
class SplitVector : public Command {
public:
SplitVector() : Command( "splitVector" , false ){}
virtual bool slaveOk() const { return false; }
virtual LockType locktype() const { return READ; }
virtual void help( stringstream &help ) const {
help <<
"Internal command.\n"
"example: { splitVector : \"myLargeCollection\" , keyPattern : {x:1} , maxChunkSize : 200 }\n"
"maxChunkSize unit in MBs\n"
"NOTE: This command may take a while to run";
}
bool run(const string& dbname, BSONObj& jsobj, string& errmsg, BSONObjBuilder& result, bool fromRepl ){
const char* ns = jsobj.getStringField( "splitVector" );
BSONObj keyPattern = jsobj.getObjectField( "keyPattern" );
long long maxChunkSize = 0;
BSONElement maxSizeElem = jsobj[ "maxChunkSize" ];
if ( ! maxSizeElem.eoo() ){
maxChunkSize = maxSizeElem.numberLong() * 1<<20;
} else {
errmsg = "need to specify the desired max chunk size";
return false;
}
Client::Context ctx( ns );
BSONObjBuilder minBuilder;
BSONObjBuilder maxBuilder;
BSONForEach(key, keyPattern){
minBuilder.appendMinKey( key.fieldName() );
maxBuilder.appendMaxKey( key.fieldName() );
}
BSONObj min = minBuilder.obj();
BSONObj max = maxBuilder.obj();
IndexDetails *idx = cmdIndexDetailsForRange( ns , errmsg , min , max , keyPattern );
if ( idx == NULL ){
errmsg = "couldn't find index over splitting key";
return false;
}
NamespaceDetails *d = nsdetails( ns );
BtreeCursor c( d , d->idxNo(*idx) , *idx , min , max , false , 1 );
// We'll use the average object size and number of object to find approximately how many keys
// each chunk should have. We'll split a little smaller than the specificied by 'maxSize'
// assuming a recently sharded collectio is still going to grow.
const long long dataSize = d->datasize;
const long long recCount = d->nrecords;
long long keyCount = 0;
if (( dataSize > 0 ) && ( recCount > 0 )){
const long long avgRecSize = dataSize / recCount;
keyCount = 90 * maxChunkSize / (100 * avgRecSize);
}
// We traverse the index and add the keyCount-th key to the result vector. If that key
// appeared in the vector before, we omit it. The assumption here is that all the
// instances of a key value live in the same chunk.
Timer timer;
long long currCount = 0;
vector<BSONObj> splitKeys;
BSONObj currKey;
while ( c.ok() ){
currCount++;
if ( currCount > keyCount ){
if ( ! currKey.isEmpty() && (currKey.woCompare( c.currKey() ) == 0 ) )
continue;
currKey = c.currKey();
splitKeys.push_back( c.prettyKey( currKey ) );
currCount = 0;
}
c.advance();
}
ostringstream os;
os << "Finding the split vector for " << ns << " over "<< keyPattern;
logIfSlow( timer , os.str() );
// Warning: we are sending back an array of keys but are currently limited to
// 4MB work of 'result' size. This should be okay for now.
result.append( "splitKeys" , splitKeys );
return true;
}
} cmdSplitVector;
} // namespace mongo
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