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// projection.h
/* Copyright 2009 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include "pch.h"
#include "jsobj.h"
namespace mongo {
/**
* given a document and a projection specification
* can transform the document
* currently supports specifying which fields and $slice
*/
class Projection {
public:
class KeyOnly {
public:
KeyOnly() : _stringSize(0) {}
BSONObj hydrate( const BSONObj& key ) const;
void addNo() { _add( false , "" ); }
void addYes( const string& name ) { _add( true , name ); }
private:
void _add( bool b , const string& name ) {
_include.push_back( b );
_names.push_back( name );
_stringSize += name.size();
}
vector<bool> _include; // one entry per field in key. true iff should be in output
vector<string> _names; // name of field since key doesn't have names
int _stringSize;
};
Projection() :
_include(true) ,
_special(false) ,
_includeID(true) ,
_skip(0) ,
_limit(-1) ,
_hasNonSimple(false) {
}
/**
* called once per lifetime
* e.g. { "x" : 1 , "a.y" : 1 }
*/
void init( const BSONObj& spec );
/**
* @return the spec init was called with
*/
BSONObj getSpec() const { return _source; }
/**
* transforms in according to spec
*/
BSONObj transform( const BSONObj& in ) const;
/**
* transforms in according to spec
*/
void transform( const BSONObj& in , BSONObjBuilder& b ) const;
/**
* @return if the keyPattern has all the information needed to return then
* return a new KeyOnly otherwise null
* NOTE: a key may have modified the actual data
* which has to be handled above this (arrays, geo)
*/
KeyOnly* checkKey( const BSONObj& keyPattern ) const;
private:
/**
* appends e to b if user wants it
* will descend into e if needed
*/
void append( BSONObjBuilder& b , const BSONElement& e ) const;
void add( const string& field, bool include );
void add( const string& field, int skip, int limit );
void appendArray( BSONObjBuilder& b , const BSONObj& a , bool nested=false) const;
bool _include; // true if default at this level is to include
bool _special; // true if this level can't be skipped or included without recursing
//TODO: benchmark vector<pair> vs map
typedef map<string, boost::shared_ptr<Projection> > FieldMap;
FieldMap _fields;
BSONObj _source;
bool _includeID;
// used for $slice operator
int _skip;
int _limit;
bool _hasNonSimple;
};
}
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