Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

199 lines (168 sloc) 6.352 kb
/**
* 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/>.
*/
#pragma once
#include "../stdafx.h"
#include "jsobj.h"
#include "storage.h"
namespace mongo {
class Record;
/* Query cursors, base class. This is for our internal cursors. "ClientCursor" is a separate
concept and is for the user's cursor.
WARNING concurrency: the vfunctions below are called back from within a
ClientCursor::ccmutex. Don't cause a deadlock, you've been warned.
*/
class Cursor {
public:
virtual ~Cursor() {}
virtual bool ok() = 0;
bool eof() {
return !ok();
}
virtual Record* _current() = 0;
virtual BSONObj current() = 0;
virtual DiskLoc currLoc() = 0;
virtual bool advance() = 0; /*true=ok*/
virtual BSONObj currKey() const { return BSONObj(); }
// DiskLoc the cursor requires for continued operation. Before this
// DiskLoc is deleted, the cursor must be incremented or destroyed.
virtual DiskLoc refLoc() = 0;
/* Implement these if you want the cursor to be "tailable" */
/* Request that the cursor starts tailing after advancing past last record. */
/* The implementation may or may not honor this request. */
virtual void setTailable() {}
/* indicates if tailing is enabled. */
virtual bool tailable() {
return false;
}
virtual void aboutToDeleteBucket(const DiskLoc& b) { }
/* optional to implement. if implemented, means 'this' is a prototype */
virtual Cursor* clone() {
return 0;
}
virtual BSONObj indexKeyPattern() {
return BSONObj();
}
/* called after every query block is iterated -- i.e. between getMore() blocks
so you can note where we are, if necessary.
*/
virtual void noteLocation() { }
/* called before query getmore block is iterated */
virtual void checkLocation() { }
virtual string toString() {
return "abstract?";
}
/* used for multikey index traversal to avoid sending back dups. see JSMatcher::matches().
if a multikey index traversal:
if loc has already been sent, returns true.
otherwise, marks loc as sent.
@param deep - match was against an array, so we know it is multikey. this is legacy and kept
for backwards datafile compatibility. 'deep' can be eliminated next time we
force a data file conversion. 7Jul09
*/
virtual bool getsetdup(DiskLoc loc) = 0;
virtual BSONObj prettyStartKey() const { return BSONObj(); }
virtual BSONObj prettyEndKey() const { return BSONObj(); }
virtual bool capped() const { return false; }
};
// strategy object implementing direction of traversal.
class AdvanceStrategy {
public:
virtual ~AdvanceStrategy() { }
virtual DiskLoc next( const DiskLoc &prev ) const = 0;
};
const AdvanceStrategy *forward();
const AdvanceStrategy *reverse();
/* table-scan style cursor */
class BasicCursor : public Cursor {
protected:
DiskLoc curr, last;
const AdvanceStrategy *s;
private:
bool tailable_;
void init() {
tailable_ = false;
}
public:
bool ok() {
return !curr.isNull();
}
Record* _current() {
assert( ok() );
return curr.rec();
}
BSONObj current() {
Record *r = _current();
BSONObj j(r);
return j;
}
virtual DiskLoc currLoc() {
return curr;
}
virtual DiskLoc refLoc() {
return curr.isNull() ? last : curr;
}
bool advance();
BasicCursor(DiskLoc dl, const AdvanceStrategy *_s = forward()) : curr(dl), s( _s ) {
init();
}
BasicCursor(const AdvanceStrategy *_s = forward()) : s( _s ) {
init();
}
virtual string toString() {
return "BasicCursor";
}
virtual void setTailable() {
if ( !curr.isNull() || !last.isNull() )
tailable_ = true;
}
virtual bool tailable() {
return tailable_;
}
virtual bool getsetdup(DiskLoc loc) { return false; }
};
/* used for order { $natural: -1 } */
class ReverseCursor : public BasicCursor {
public:
ReverseCursor(DiskLoc dl) : BasicCursor( dl, reverse() ) { }
ReverseCursor() : BasicCursor( reverse() ) { }
virtual string toString() {
return "ReverseCursor";
}
};
class NamespaceDetails;
class ForwardCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ForwardCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ForwardCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
class ReverseCappedCursor : public BasicCursor, public AdvanceStrategy {
public:
ReverseCappedCursor( NamespaceDetails *nsd = 0, const DiskLoc &startLoc = DiskLoc() );
virtual string toString() {
return "ReverseCappedCursor";
}
virtual DiskLoc next( const DiskLoc &prev ) const;
virtual bool capped() const { return true; }
private:
NamespaceDetails *nsd;
};
} // namespace mongo
Jump to Line
Something went wrong with that request. Please try again.