path: root/db/query.cpp

// query.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 "stdafx.h"
#include "query.h"
#include "pdfile.h"
#include "jsobj.h"
#include "../util/builder.h"
#include <time.h>
#include "introspect.h"
#include "btree.h"
#include "../util/lruishmap.h"
#include "javajs.h"
#include "json.h"
#include "repl.h"
#include "replset.h"
#include "scanandorder.h"

/* We cut off further objects once we cross this threshold; thus, you might get 
   a little bit more than this, it is a threshold rather than a limit.
*/
const int MaxBytesToReturnToClientAtOnce = 4 * 1024 * 1024;

//ns->query->DiskLoc
LRUishMap<BSONObj,DiskLoc,5> lrutest(123);

int nextCursorId = 1;
extern bool useCursors;

int getGtLtOp(BSONElement& e);
void appendElementHandlingGtLt(BSONObjBuilder& b, BSONElement& e);

/* todo: _ cache query plans 
         _ use index on partial match with the query

   parameters
     query - the query, e.g., { name: 'joe' }
     order - order by spec, e.g., { name: 1 } 1=ASC, -1=DESC
     simpleKeyMatch - set to true if the query is purely for a single key value
                      unchanged otherwise.
*/
auto_ptr<Cursor> getIndexCursor(const char *ns, BSONObj& query, BSONObj& order, bool *simpleKeyMatch = 0, bool *isSorted = 0, string *hint = 0) { 
	NamespaceDetails *d = nsdetails(ns);
	if( d == 0 ) return auto_ptr<Cursor>();

    if( hint && !hint->empty() ) { 
        /* todo: more work needed.  doesn't handle $lt & $gt for example.
                 waiting for query optimizer rewrite (see queryoptimizer.h) before finishing the work.
        */
        for(int i = 0; i < d->nIndexes; i++ ) { 
            IndexDetails& ii = d->indexes[i];
            if( ii.indexName() == *hint ) {
                BSONObj startKey = ii.getKeyFromQuery(query);
                int direction = 1;
                bool stopMiss = true;
                if( simpleKeyMatch ) 
                    *simpleKeyMatch = query.nFields() == startKey.nFields();
                if( isSorted ) *isSorted = false;
                return auto_ptr<Cursor>( 
                    new BtreeCursor(ii, startKey, direction, stopMiss));
            }
        }
    }

	if( !order.isEmpty() ) {
		set<string> orderFields;
		order.getFieldNames(orderFields);
		// order by
		for(int i = 0; i < d->nIndexes; i++ ) { 
			BSONObj idxInfo = d->indexes[i].info.obj(); // { name:, ns:, key: }
			assert( strcmp(ns, idxInfo.getStringField("ns")) == 0 );
			BSONObj idxKey = idxInfo.getObjectField("key");
			set<string> keyFields;
			idxKey.getFieldNames(keyFields);
			if( keyFields == orderFields ) {
				bool reverse = 
					order.firstElement().number() < 0;
				BSONObjBuilder b;
				/* todo: start with the right key, not just beginning of index, when query is also
				         specified!
				*/
				DEV cout << " using index " << d->indexes[i].indexNamespace() << '\n';
				if( isSorted )
					*isSorted = true;
				return auto_ptr<Cursor>(new BtreeCursor(d->indexes[i], reverse ? maxKey : emptyObj, reverse ? -1 : 1, false));
			}
		}
	}

	// queryFields, e.g. { 'name' }
	set<string> queryFields;
	query.getFieldNames(queryFields);

	// regular query without order by
	for(int i = 0; i < d->nIndexes; i++ ) { 
		BSONObj idxInfo = d->indexes[i].info.obj(); // { name:, ns:, key: }
		BSONObj idxKey = idxInfo.getObjectField("key");
		set<string> keyFields;
		idxKey.getFieldNames(keyFields);

        // keyFields: e.g. { "name" }
        bool match = keyFields == queryFields;
        if( 0 && !match && queryFields.size() > 1 && simpleKeyMatch == 0 && keyFields.size() == 1 ) { 
            // TEMP
            string s = *(keyFields.begin());
            match = queryFields.count(s) == 1;
        }

        if( match ) {
			bool simple = true;
			//BSONObjBuilder b;
			BSONObj q = query.extractFieldsUnDotted(idxKey);
            assert(q.objsize() != 0); // guard against a seg fault if details is 0
			/* regexp: only supported if form is /^text/ */
			BSONObjBuilder b2;
			BSONObjIterator it(q);
			bool first = true;
			while( it.more() ) {
				BSONElement e = it.next();
				if( e.eoo() )
					break;

				// GT/LT
				if( e.type() == Object ) { 
					int op = getGtLtOp(e);
					if( op ) { 
						if( !first || !it.next().eoo() ) {
							// compound keys with GT/LT not supported yet via index.
							goto fail;
						}
						if( op >= JSMatcher::opIN ) {
							// $in does not use an index (at least yet, should when # of elems is tiny)
                            // likewise $ne
							goto fail;
						}

						{
							BSONObjIterator k(e.embeddedObject());
							k.next();
							if( !k.next().eoo() ) { 
								/* compound query like { $lt : 9, $gt : 2 } 
								   for those our method below won't work.
								   need more work on "stopOnMiss" in general -- may
								   be issues with it.  so fix this to use index after
								   that is fixed. 
								*/
								OCCASIONALLY cout << "finish query optimizer for lt gt compound\n";
								goto fail;
							}
						}

						int direction = - JSMatcher::opDirection(op);
						return auto_ptr<Cursor>( new BtreeCursor(
							d->indexes[i], 
							direction == 1 ? emptyObj : maxKey, 
							direction, 
							true) );
					}
				}

				first = false;
				if( e.type() == RegEx ) { 
					simple = false;
					if( *e.regexFlags() )
						goto fail;
					const char *re = e.regex();
					const char *p = re;
					if( *p++ != '^' ) goto fail;
					while( *p ) {
						if( *p == ' ' || (*p>='0'&&*p<='9') || (*p>='@'&&*p<='Z') || (*p>='a'&&*p<='z') )
							;
						else
							goto fail;
						p++;
					}
					if( it.more() && !it.next().eoo() ) // we must be the last part of the key (for now until we are smarter)
						goto fail;
					// ok!
                    b2.append(e.fieldName(), re+1);
					break;
				}
				else {
					b2.append(e);
					//appendElementHandlingGtLt(b2, e);
				}
			}
			BSONObj q2 = b2.done();
			DEV cout << "using index " << d->indexes[i].indexNamespace() << endl;
			if( simple && simpleKeyMatch ) *simpleKeyMatch = true;
			return auto_ptr<Cursor>( 
				new BtreeCursor(d->indexes[i], q2, 1, true));
		}
	}

fail:
	DEV cout << "getIndexCursor fail " << ns << '\n';
	return auto_ptr<Cursor>();
}

/* ns:      namespace, e.g. <client>.<collection>
   pattern: the "where" clause / criteria
   justOne: stop after 1 match
*/
int deleteObjects(const char *ns, BSONObj pattern, bool justOne, bool god) {
	if( strstr(ns, ".system.") && !god ) {
		/*if( strstr(ns, ".system.namespaces") ){ 
			cout << "info: delete on system namespace " << ns << '\n';
		}
		else if( strstr(ns, ".system.indexes") ) {
			cout << "info: delete on system namespace " << ns << '\n';
		}
		else*/ { 
			cout << "ERROR: attempt to delete in system namespace " << ns << endl;
			return -1;
		}
	}

	int nDeleted = 0;
	JSMatcher matcher(pattern);
	BSONObj order;
	auto_ptr<Cursor> c = getIndexCursor(ns, pattern, order);
	if( c.get() == 0 )
		c = theDataFileMgr.findAll(ns);

	Cursor &tempDebug = *c;

	while( c->ok() ) {
		Record *r = c->_current();
		DiskLoc rloc = c->currLoc();
		c->advance(); // must advance before deleting as the next ptr will die
		BSONObj js(r);

		bool deep;
		if( !matcher.matches(js, &deep) ) {
			if( c->tempStopOnMiss() )
				break;
		}
		else { 
			assert( !deep || !c->getsetdup(rloc) ); // can't be a dup, we deleted it!
			if( !justOne )
				c->noteLocation();

			theDataFileMgr.deleteRecord(ns, r, rloc);
			nDeleted++;
			if( justOne )
				break;
			c->checkLocation();
		}
	}

	return nDeleted;
}

struct Mod { 
	enum Op { INC, SET } op;
	const char *fieldName;
    double *ndouble;
    int *nint;
    void setn(double n) { 
        if( ndouble ) *ndouble = n;
        else *nint = (int) n;
    }
    double getn() { return ndouble ? *ndouble : *nint; }
    int type;
	static void getMods(vector<Mod>& mods, BSONObj from);
	static void applyMods(vector<Mod>& mods, BSONObj obj);
};

void Mod::applyMods(vector<Mod>& mods, BSONObj obj) { 
	for( vector<Mod>::iterator i = mods.begin(); i != mods.end(); i++ ) { 
		Mod& m = *i;
		BSONElement e = obj.findElement(m.fieldName);
		if( e.isNumber() ) {
            if( m.op == INC ) {
                e.setNumber( e.number() + m.getn() );
                m.setn( e.number() );
				// *m.n = e.number() += *m.n;
            } else {
                e.setNumber( m.getn() ); // $set or $SET
            }
		}
	}
}

/* get special operations like $inc 
   { $inc: { a:1, b:1 } }
   { $set: { a:77 } }
   NOTE: MODIFIES source from object!
*/
void Mod::getMods(vector<Mod>& mods, BSONObj from) { 
	BSONObjIterator it(from);
	while( it.more() ) {
		BSONElement e = it.next();
		const char *fn = e.fieldName();
		if( *fn == '$' && e.type() == Object && 
			fn[4] == 0 ) {
			BSONObj j = e.embeddedObject();
			BSONObjIterator jt(j);
			Op op = Mod::SET;
			if( strcmp("$inc",fn) == 0 ) {
				op = Mod::INC;
				// we rename to $SET instead of $set so that on an op like
				//   { $set: {x:1}, $inc: {y:1} }
				// we don't get two "$set" fields which isn't allowed
				strcpy((char *) fn, "$SET");
			}
			while( jt.more() ) { 
				BSONElement f = jt.next();
				if( f.eoo() )
					break;
				Mod m;
				m.op = op;
				m.fieldName = f.fieldName();
                if( f.isNumber() ) {
                    if( f.type() == NumberDouble ) {
                        m.ndouble = (double *) f.value();
                        m.nint = 0;
                    }
                    else { 
                        m.ndouble = 0;
                        m.nint = (int *) f.value();
                    }
					mods.push_back( m );
				} 
			}
		}
	}
}

/* todo:
     _ smart requery find record immediately
   returns:  
     2: we did applyMods() but didn't logOp()
	 5: we did applyMods() and did logOp() (so don't do it again) 
     (clean these up later...)
*/
int _updateObjects(const char *ns, BSONObj updateobj, BSONObj pattern, bool upsert, stringstream& ss, bool logop=false) {
	//cout << "TEMP BAD";
	//lrutest.find(updateobj);

	int profile = client->profile;

	//	cout << "update ns:" << ns << " objsize:" << updateobj.objsize() << " queryobjsize:" << 
	//		pattern.objsize();

	if( strstr(ns, ".system.") ) { 
		cout << "\nERROR: attempt to update in system namespace " << ns << endl;
		ss << " can't update system namespace ";
		return 0;
	}

	int nscanned = 0;
	{
		JSMatcher matcher(pattern);
		BSONObj order;
		auto_ptr<Cursor> c = getIndexCursor(ns, pattern, order);
		if( c.get() == 0 )
			c = theDataFileMgr.findAll(ns);
		while( c->ok() ) {
			Record *r = c->_current();
			nscanned++;
			BSONObj js(r);
			if( !matcher.matches(js) ) {
				if( c->tempStopOnMiss() )
					break;
			}
			else {
				/* note: we only update one row and quit.  if you do multiple later, 
				   be careful or multikeys in arrays could break things badly.  best 
				   to only allow updating a single row with a multikey lookup.
				   */

				if( profile )
					ss << " nscanned:" << nscanned;

				/* look for $inc etc.  note as listed here, all fields to inc must be this type, you can't set some
				   regular ones at the moment. */
				const char *firstField = updateobj.firstElement().fieldName();
				if( firstField[0] == '$' ) {
					vector<Mod> mods;
					Mod::getMods(mods, updateobj);
                    NamespaceDetailsTransient& ndt = NamespaceDetailsTransient::get(ns);
                    set<string>& idxKeys = ndt.indexKeys();
                    for( vector<Mod>::iterator i = mods.begin(); i != mods.end(); i++ ) { 
                        if( idxKeys.count(i->fieldName) ) {
                            uassert("can't $inc/$set an indexed field", false);
                        }
                    }

					Mod::applyMods(mods, c->currLoc().obj());
					if( profile ) 
						ss << " fastmod ";
					if( logop ) {
						if( mods.size() ) { 
							logOp("u", ns, updateobj, &pattern, &upsert);
							return 5;
						}
					}
					return 2;
				}

				theDataFileMgr.update(ns, r, c->currLoc(), updateobj.objdata(), updateobj.objsize(), ss);
				return 1;
			}
			c->advance();
		}
	}

	if( profile )
		ss << " nscanned:" << nscanned;

	if( upsert ) {
		if( updateobj.firstElement().fieldName()[0] == '$' ) {
			/* upsert of an $inc. build a default */
			vector<Mod> mods;
			Mod::getMods(mods, updateobj);
			BSONObjBuilder b;
			b.appendElements(pattern);
			for( vector<Mod>::iterator i = mods.begin(); i != mods.end(); i++ )
				b.append(i->fieldName, i->getn());
			BSONObj obj = b.done();
			theDataFileMgr.insert(ns, (void*) obj.objdata(), obj.objsize());
			if( profile )
				ss << " fastmodinsert ";
			return 3;
		}
		if( profile )
			ss << " upsert ";
		theDataFileMgr.insert(ns, (void*) updateobj.objdata(), updateobj.objsize());
		return 4;
	}
	return 0;
}
/* todo: we can optimize replication by just doing insert when an upsert triggers. 
*/
void updateObjects(const char *ns, BSONObj updateobj, BSONObj pattern, bool upsert, stringstream& ss) {
	int rc = _updateObjects(ns, updateobj, pattern, upsert, ss, true);
	if( rc != 5 )
		logOp("u", ns, updateobj, &pattern, &upsert);
}

int queryTraceLevel = 0;
int otherTraceLevel = 0;

int initialExtentSize(int len);

bool _runCommands(const char *ns, BSONObj& jsobj, stringstream& ss, BufBuilder &b, BSONObjBuilder& anObjBuilder);

bool runCommands(const char *ns, BSONObj& jsobj, stringstream& ss, BufBuilder &b, BSONObjBuilder& anObjBuilder) { 
	try {
		return _runCommands(ns, jsobj, ss, b, anObjBuilder);
	}
	catch( AssertionException e ) {
        if( !e.msg.empty() ) 
            anObjBuilder.append("assertion", e.msg);
	}
	ss << " assertion ";
	anObjBuilder.append("errmsg", "db assertion failure");
	anObjBuilder.append("ok", 0.0);
	BSONObj x = anObjBuilder.done();
	b.append((void*) x.objdata(), x.objsize());
	return true;
}

int nCaught = 0;

void killCursors(int n, long long *ids) {
	int k = 0;
	for( int i = 0; i < n; i++ ) {
		if( ClientCursor::erase(ids[i]) )
			k++;
	}
	log() << "killCursors: found " << k << " of " << n << '\n';
}

// order.$natural sets natural order direction
auto_ptr<Cursor> findTableScan(const char *ns, BSONObj& order, bool *isSorted=0);

BSONObj id_obj = fromjson("{_id:ObjId()}");
BSONObj empty_obj = fromjson("{}");

/* { count: "collectionname"[, query: <query>] } 
   returns -1 on error.
*/
int runCount(const char *ns, BSONObj& cmd, string& err) { 
	NamespaceDetails *d = nsdetails(ns);
	if( d == 0 ) {
		err = "ns does not exist";
		return -1;
	}

	BSONObj query = cmd.getObjectField("query");

	if( query.isEmpty() ) { 
		// count of all objects
		return (int) d->nrecords;
	}

	auto_ptr<Cursor> c;

	bool simpleKeyToMatch = false;
	c = getIndexCursor(ns, query, empty_obj, &simpleKeyToMatch);

	if( c.get() ) {
		if( simpleKeyToMatch ) { 
			/* Here we only look at the btree keys to determine if a match, instead of looking 
			   into the records, which would be much slower.
			   */
			int count = 0;
			BtreeCursor *bc = dynamic_cast<BtreeCursor *>(c.get());
			if( c->ok() ) {
				while( 1 ) {
					if( !(query == bc->currKeyNode().key) )
						break;
					count++;
					if( !c->advance() )
						break;
				}
			}
			return count;
		}
	} else {
		c = findTableScan(ns, empty_obj);
	}

	int count = 0;
	auto_ptr<JSMatcher> matcher(new JSMatcher(query));
	while( c->ok() ) {
		BSONObj js = c->current();
		bool deep;
		if( !matcher->matches(js, &deep) ) {
			if( c->tempStopOnMiss() )
				break;
		}
		else if( !deep || !c->getsetdup(c->currLoc()) ) { // i.e., check for dups on deep items only
			// got a match.
			count++;
		}
		c->advance();
	}
	return count;
}

/* This is for languages whose "objects" are not well ordered (JSON is well ordered).
   [ { a : ... } , { b : ... } ] -> { a : ..., b : ... } 
*/
inline BSONObj transformOrderFromArrayFormat(BSONObj order) { 
    /* note: this is slow, but that is ok as order will have very few pieces */
    BSONObjBuilder b;
    char p[2] = "0";

    while( 1 ) {
        BSONObj j = order.getObjectField(p);
        if( j.isEmpty() ) 
            break;
        BSONElement e = j.firstElement();
        uassert("bad order array", !e.eoo());
        uassert("bad order array [2]", e.isNumber());
        b.append(e);
        (*p)++;
        uassert("too many ordering elements", *p <= '9');
    }

    return b.doneAndDecouple();
}

QueryResult* runQuery(Message& message, const char *ns, int ntoskip, int _ntoreturn, BSONObj jsobj, 
					  auto_ptr< set<string> > filter, stringstream& ss, int queryOptions) 
{
    Timer t;
    int nscanned = 0;
	bool wantMore = true;
	int ntoreturn = _ntoreturn;
	if( _ntoreturn < 0 ) {
		ntoreturn = -_ntoreturn;
		wantMore = false;
	}
	ss << "query " << ns << " ntoreturn:" << ntoreturn;

	int n = 0;
	BufBuilder b(32768);
	BSONObjBuilder cmdResBuf;
	long long cursorid = 0;

	b.skip(sizeof(QueryResult));

	/* we assume you are using findOne() for running a cmd... */
	if( ntoreturn == 1 && runCommands(ns, jsobj, ss, b, cmdResBuf) ) { 
		n = 1;
	}
	else {

        uassert("not master", isMaster() || (queryOptions & Option_SlaveOk));

        string hint;
        bool explain = false;
        bool _gotquery = false;
		BSONObj query;// = jsobj.getObjectField("query");
        {
            BSONElement e = jsobj.findElement("query");
            if( !e.eoo() && (e.type() == Object || e.type() == Array) ) {
                query = e.embeddedObject();
                _gotquery = true;
            }
        }
        BSONObj order;
        {
            BSONElement e = jsobj.findElement("orderby");
            if( !e.eoo() ) {
                order = e.embeddedObjectUserCheck();
                if( e.type() == Array ) 
                    order = transformOrderFromArrayFormat(order);
            }
        }
		if( !_gotquery && order.isEmpty() )
			query = jsobj;
        else {
            explain = jsobj.getBoolField("$explain");
            hint = jsobj.getStringField("$hint");
        }

		/* The ElemIter will not be happy if this isn't really an object. So throw exception
		   here when that is true.
 		   (Which may indicate bad data from appserver?)
		*/
		if( query.objsize() == 0 ) { 
			cout << "Bad query object?\n  jsobj:";
			cout << jsobj.toString() << "\n  query:";
			cout << query.toString() << endl;
            uassert("bad query object", false);
		}

		auto_ptr<JSMatcher> matcher(new JSMatcher(query));
		JSMatcher &debug1 = *matcher;
		assert( debug1.getN() < 5000 );

		bool isSorted = false;
		auto_ptr<Cursor> c = getSpecialCursor(ns);

		if( c.get() == 0 )
			c = getIndexCursor(ns, query, order, 0, &isSorted, &hint);
		if( c.get() == 0 )
			c = findTableScan(ns, order, &isSorted);

		auto_ptr<ScanAndOrder> so;
		bool ordering = false;
		if( !order.isEmpty() && !isSorted ) {
			ordering = true;
			ss << " scanAndOrder ";
			so = auto_ptr<ScanAndOrder>(new ScanAndOrder(ntoskip, ntoreturn,order));
			wantMore = false;
			//			scanAndOrder(b, c.get(), order, ntoreturn);
		}

		while( c->ok() ) {
			BSONObj js = c->current();
			//if( queryTraceLevel >= 50 )
			//	cout << " checking against:\n " << js.toString() << endl;
			nscanned++;
			bool deep;

			if( !matcher->matches(js, &deep) ) {
				if( c->tempStopOnMiss() )
					break;
			}
			else if( !deep || !c->getsetdup(c->currLoc()) ) { // i.e., check for dups on deep items only
				// got a match.
                assert( js.objsize() >= 0 ); //defensive for segfaults
                if( ordering ) {
                    // note: no cursors for non-indexed, ordered results.  results must be fairly small.
                    so->add(js);
                }
                else if( ntoskip > 0 ) {
                    ntoskip--;
                } else { 
                    if( explain ) {
                        n++;
                    }
                    else {
                        bool ok = fillQueryResultFromObj(b, filter.get(), js);
                        if( ok ) n++;
                        if( ok ) {
                            if( (ntoreturn>0 && (n >= ntoreturn || b.len() > MaxBytesToReturnToClientAtOnce)) ||
                                (ntoreturn==0 && (b.len()>1*1024*1024 || n>=101)) ) {
                                    /* if ntoreturn is zero, we return up to 101 objects.  on the subsequent getmore, there 
                                    is only a size limit.  The idea is that on a find() where one doesn't use much results, 
                                    we don't return much, but once getmore kicks in, we start pushing significant quantities.

                                    The n limit (vs. size) is important when someone fetches only one small field from big 
                                    objects, which causes massive scanning server-side.
                                    */
                                    /* if only 1 requested, no cursor saved for efficiency...we assume it is findOne() */
                                    if( wantMore && ntoreturn != 1 ) {
                                        if( useCursors ) {
                                            c->advance();
                                            if( c->ok() ) {
                                                // more...so save a cursor
                                                ClientCursor *cc = new ClientCursor();
                                                cc->c = c;
                                                cursorid = cc->cursorid;
                                                DEV cout << "  query has more, cursorid: " << cursorid << endl;
                                                cc->matcher = matcher;
                                                cc->ns = ns;
                                                cc->pos = n;
                                                cc->filter = filter;
                                                cc->originalMessage = message;
                                                cc->updateLocation();
                                            }
                                        }
                                    }
                                    break;
                            }
                        }
                    }
                }
			}
			c->advance();
		} // end while

        if( explain ) {
            BSONObjBuilder builder;
            builder.append("cursor", c->toString());
            builder.append("nscanned", nscanned);
            builder.append("n", ordering ? so->size() : n);
            if( ordering ) 
                builder.append("scanAndOrder", true);
            builder.append("millis", t.millis());
            BSONObj obj = builder.done();
            fillQueryResultFromObj(b, 0, obj);
            n = 1;
        } else if( ordering ) { 
            so->fill(b, filter.get(), n);
		}
		else if( cursorid == 0 && (queryOptions & Option_CursorTailable) && c->tailable() ) { 
			c->setAtTail();
			ClientCursor *cc = new ClientCursor();
			cc->c = c;
			cursorid = cc->cursorid;
			DEV cout << "  query has no more but tailable, cursorid: " << cursorid << endl;
			cc->matcher = matcher;
			cc->ns = ns;
			cc->pos = n;
			cc->filter = filter;
			cc->originalMessage = message;
			cc->updateLocation();
		}
	}

	QueryResult *qr = (QueryResult *) b.buf();
	qr->_data[0] = 0;
	qr->_data[1] = 0;
	qr->_data[2] = 0;
	qr->_data[3] = 0;
	qr->len = b.len();
	ss << " reslen:" << b.len();
	//	qr->channel = 0;
	qr->setOperation(opReply);
	qr->cursorId = cursorid;
	qr->startingFrom = 0;
	qr->nReturned = n;
	b.decouple();

    int duration = t.millis();
	if( (client && client->profile) || duration >= 100 ) {
        ss << " nscanned:" << nscanned << ' ';
		if( ntoskip ) 
			ss << " ntoskip:" << ntoskip;
        if( client && client->profile )
            ss << " <br>query: ";
        ss << jsobj.toString() << ' ';
	}
	ss << " nreturned:" << n;
	return qr;
}

//int dump = 0;

/* empty result for error conditions */
QueryResult* emptyMoreResult(long long cursorid) {
	BufBuilder b(32768);
	b.skip(sizeof(QueryResult));
	QueryResult *qr = (QueryResult *) b.buf();
	qr->cursorId = 0; // 0 indicates no more data to retrieve.
	qr->startingFrom = 0;
	qr->len = b.len();
	qr->setOperation(opReply);
	qr->nReturned = 0;
	b.decouple();
	return qr;
}

QueryResult* getMore(const char *ns, int ntoreturn, long long cursorid) {
	BufBuilder b(32768);

	ClientCursor *cc = ClientCursor::find(cursorid);

	b.skip(sizeof(QueryResult));

	int resultFlags = 0;
	int start = 0;
	int n = 0;

	if( !cc ) { 
		DEV log() << "getMore: cursorid not found " << ns << " " << cursorid << endl;
		cursorid = 0;
		resultFlags = ResultFlag_CursorNotFound;
	}
	else {
		start = cc->pos;
		Cursor *c = cc->c.get();
		c->checkLocation();
		c->tailResume();
		while( 1 ) {
			if( !c->ok() ) {
done:
				if( c->tailing() ) {
					c->setAtTail();
					break;
				}
				DEV log() << "  getmore: last batch, erasing cursor " << cursorid << endl;
				bool ok = ClientCursor::erase(cursorid);
				assert(ok);
				cursorid = 0;
				cc = 0;
				break;
			}
			BSONObj js = c->current();

			bool deep;

			if( !cc->matcher->matches(js, &deep) ) {
				if( c->tempStopOnMiss() )
					goto done;
			} 
			else { 
				//cout << "matches " << c->currLoc().toString() << ' ' << deep << '\n';
				if( deep && c->getsetdup(c->currLoc()) ) { 
					//cout << "  but it's a dup \n";
				}
				else {
					bool ok = fillQueryResultFromObj(b, cc->filter.get(), js);
					if( ok ) {
						n++;
						if( (ntoreturn>0 && (n >= ntoreturn || b.len() > MaxBytesToReturnToClientAtOnce)) ||
							(ntoreturn==0 && b.len()>1*1024*1024) ) {
								c->advance();
								if( c->tailing() && !c->ok() )
									c->setAtTail();
								cc->pos += n;
								//cc->updateLocation();
								break;
						}
					}
				}
			}
			c->advance();
		}
        if( cc ) 
            cc->updateLocation();
	}

	QueryResult *qr = (QueryResult *) b.buf();
	qr->len = b.len();
	qr->setOperation(opReply);
	qr->resultFlags() = resultFlags;
	qr->cursorId = cursorid;
	qr->startingFrom = start;
	qr->nReturned = n;
	b.decouple();

	return qr;
}