93 lines
3.1 KiB
C++
93 lines
3.1 KiB
C++
/* scanandorder.cpp
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Order results (that aren't already indexes and in order.)
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*/
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/**
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* Copyright (C) 2008 10gen Inc.
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License, version 3,
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* as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "pch.h"
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#include "scanandorder.h"
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namespace mongo {
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const unsigned ScanAndOrder::MaxScanAndOrderBytes = 32 * 1024 * 1024;
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void ScanAndOrder::_add(BSONObj& k, BSONObj o, DiskLoc* loc) {
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if (!loc) {
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_best.insert(make_pair(k.getOwned(),o.getOwned()));
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}
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else {
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BSONObjBuilder b;
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b.appendElements(o);
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b.append("$diskLoc", loc->toBSONObj());
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_best.insert(make_pair(k.getOwned(), b.obj().getOwned()));
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}
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}
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void ScanAndOrder::_addIfBetter(BSONObj& k, BSONObj o, BestMap::iterator i, DiskLoc* loc) {
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/* todo : we don't correct _approxSize here. */
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const BSONObj& worstBestKey = i->first;
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int c = worstBestKey.woCompare(k, _order._spec.keyPattern);
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if ( c > 0 ) {
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// k is better, 'upgrade'
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_best.erase(i);
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_add(k, o, loc);
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}
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}
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void ScanAndOrder::add(BSONObj o, DiskLoc* loc) {
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assert( o.isValid() );
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BSONObj k = _order.getKeyFromObject(o);
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if ( k.isEmpty() ) {
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return;
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}
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if ( (int) _best.size() < _limit ) {
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_approxSize += k.objsize();
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_approxSize += o.objsize();
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/* note : adjust when bson return limit adjusts. note this limit should be a bit higher. */
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uassert( 10128 , "too much data for sort() with no index. add an index or specify a smaller limit", _approxSize < MaxScanAndOrderBytes );
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_add(k, o, loc);
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return;
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}
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BestMap::iterator i;
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assert( _best.end() != _best.begin() );
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i = _best.end();
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i--;
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_addIfBetter(k, o, i, loc);
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}
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void ScanAndOrder::fill(BufBuilder& b, Projection *filter, int& nout ) const {
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int n = 0;
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int nFilled = 0;
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for ( BestMap::const_iterator i = _best.begin(); i != _best.end(); i++ ) {
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n++;
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if ( n <= _startFrom )
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continue;
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const BSONObj& o = i->second;
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fillQueryResultFromObj(b, filter, o);
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nFilled++;
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if ( nFilled >= _limit )
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break;
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uassert( 10129 , "too much data for sort() with no index", b.len() < (int)MaxScanAndOrderBytes ); // appserver limit
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}
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nout = nFilled;
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}
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} // namespace mongo
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