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/**
* Copyright (c) 2011 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/>.
*/
#pragma once
#include "mongo/pch.h"
#include <boost/unordered_set.hpp>
#include "db/pipeline/value.h"
#include "db/pipeline/expression.h"
#include "bson/bsontypes.h"
namespace mongo {
class ExpressionContext;
class Accumulator :
public ExpressionNary {
public:
// virtuals from ExpressionNary
virtual void addOperand(const intrusive_ptr<Expression> &pExpression);
virtual void addToBsonObj(BSONObjBuilder *pBuilder,
StringData fieldName,
bool requireExpression) const;
virtual void addToBsonArray(BSONArrayBuilder *pBuilder) const;
/*
Get the accumulated value.
@returns the accumulated value
*/
virtual Value getValue() const = 0;
protected:
Accumulator();
/*
Convenience method for doing this for accumulators. The pattern
is always the same, so a common implementation works, but requires
knowing the operator name.
@param pBuilder the builder to add to
@param fieldName the projected name
@param opName the operator name
*/
void opToBson(BSONObjBuilder *pBuilder, StringData opName,
StringData fieldName, bool requireExpression) const;
};
class AccumulatorAddToSet :
public Accumulator {
public:
// virtuals from Expression
virtual Value evaluate(const Document& pDocument) const;
virtual Value getValue() const;
virtual const char *getOpName() const;
/*
Create an appending accumulator.
@param pCtx the expression context
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
AccumulatorAddToSet(const intrusive_ptr<ExpressionContext> &pTheCtx);
typedef boost::unordered_set<Value, Value::Hash > SetType;
mutable SetType set;
mutable SetType::iterator itr;
intrusive_ptr<ExpressionContext> pCtx;
};
/*
This isn't a finished accumulator, but rather a convenient base class
for others such as $first, $last, $max, $min, and similar. It just
provides a holder for a single Value, and the getter for that. The
holder is protected so derived classes can manipulate it.
*/
class AccumulatorSingleValue :
public Accumulator {
public:
// virtuals from Expression
virtual Value getValue() const;
protected:
AccumulatorSingleValue();
mutable Value pValue; /* current min/max */
};
class AccumulatorFirst :
public AccumulatorSingleValue {
public:
// virtuals from Expression
virtual Value evaluate(const Document& pDocument) const;
virtual const char *getOpName() const;
/*
Create the accumulator.
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
mutable bool _haveFirst;
AccumulatorFirst();
};
class AccumulatorLast :
public AccumulatorSingleValue {
public:
// virtuals from Expression
virtual Value evaluate(const Document& pDocument) const;
virtual const char *getOpName() const;
/*
Create the accumulator.
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
AccumulatorLast();
};
class AccumulatorSum :
public Accumulator {
public:
// virtuals from Accumulator
virtual Value evaluate(const Document& pDocument) const;
virtual Value getValue() const;
virtual const char *getOpName() const;
/*
Create a summing accumulator.
@param pCtx the expression context
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
protected: /* reused by AccumulatorAvg */
AccumulatorSum();
mutable BSONType totalType;
mutable long long longTotal;
mutable double doubleTotal;
// count is only used by AccumulatorAvg, but lives here to avoid counting non-numeric values
mutable long long count;
};
class AccumulatorMinMax :
public AccumulatorSingleValue {
public:
// virtuals from Expression
virtual Value evaluate(const Document& pDocument) const;
virtual const char *getOpName() const;
/*
Create either the max or min accumulator.
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> createMin(
const intrusive_ptr<ExpressionContext> &pCtx);
static intrusive_ptr<Accumulator> createMax(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
AccumulatorMinMax(int theSense);
int sense; /* 1 for min, -1 for max; used to "scale" comparison */
};
class AccumulatorPush :
public Accumulator {
public:
// virtuals from Expression
virtual Value evaluate(const Document& pDocument) const;
virtual Value getValue() const;
virtual const char *getOpName() const;
/*
Create an appending accumulator.
@param pCtx the expression context
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
AccumulatorPush(const intrusive_ptr<ExpressionContext> &pTheCtx);
mutable vector<Value> vpValue;
intrusive_ptr<ExpressionContext> pCtx;
};
class AccumulatorAvg :
public AccumulatorSum {
typedef AccumulatorSum Super;
public:
// virtuals from Accumulator
virtual Value evaluate(const Document& pDocument) const;
virtual Value getValue() const;
virtual const char *getOpName() const;
/*
Create an averaging accumulator.
@param pCtx the expression context
@returns the created accumulator
*/
static intrusive_ptr<Accumulator> create(
const intrusive_ptr<ExpressionContext> &pCtx);
private:
static const char subTotalName[];
static const char countName[];
AccumulatorAvg(const intrusive_ptr<ExpressionContext> &pCtx);
intrusive_ptr<ExpressionContext> pCtx;
};
}
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