// delete.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 "pch.h"
#include "delete.h"
#include "../queryutil.h"
#include "../oplog.h"
#include "mongo/client/dbclientinterface.h"
#include "mongo/util/stacktrace.h"

namespace mongo {
    
    /* ns:      namespace, e.g. <database>.<collection>
       pattern: the "where" clause / criteria
       justOne: stop after 1 match
       god:     allow access to system namespaces, and don't yield
    */
    long long deleteObjects(const char *ns, BSONObj pattern, bool justOne, bool logop, bool god, RemoveSaver * rs ) {
        if( !god ) {
            if ( strstr(ns, ".system.") ) {
                /* note a delete from system.indexes would corrupt the db
                if done here, as there are pointers into those objects in
                NamespaceDetails.
                */
                uassert(12050, "cannot delete from system namespace", legalClientSystemNS( ns , true ) );
            }
            if ( strchr( ns , '$' ) ) {
                log() << "cannot delete from collection with reserved $ in name: " << ns << endl;
                uassert( 10100 ,  "cannot delete from collection with reserved $ in name", strchr(ns, '$') == 0 );
            }
        }

        {
            NamespaceDetails *d = nsdetails( ns );
            if ( ! d )
                return 0;
            uassert( 10101 ,  "can't remove from a capped collection" , ! d->isCapped() );
        }

        long long nDeleted = 0;

        shared_ptr< Cursor > creal = NamespaceDetailsTransient::getCursor( ns, pattern );

        if( !creal->ok() )
            return nDeleted;

        shared_ptr< Cursor > cPtr = creal;
        auto_ptr<ClientCursor> cc( new ClientCursor( QueryOption_NoCursorTimeout, cPtr, ns) );
        cc->setDoingDeletes( true );

        CursorId id = cc->cursorid();

        bool canYield = !god && !(creal->matcher() && creal->matcher()->docMatcher().atomic());

        do {
            // TODO: we can generalize this I believe
            //       
            bool willNeedRecord = (creal->matcher() && creal->matcher()->needRecord()) || pattern.isEmpty() || isSimpleIdQuery( pattern );
            if ( ! willNeedRecord ) {
                // TODO: this is a total hack right now
                // check if the index full encompasses query
                
                if ( pattern.nFields() == 1 && 
                     str::equals( pattern.firstElement().fieldName() , creal->indexKeyPattern().firstElement().fieldName() ) )
                    willNeedRecord = true;
            }
            
            if ( canYield && ! cc->yieldSometimes( willNeedRecord ? ClientCursor::WillNeed : ClientCursor::MaybeCovered ) ) {
                cc.release(); // has already been deleted elsewhere
                // TODO should we assert or something?
                break;
            }
            if ( !cc->ok() ) {
                break; // if we yielded, could have hit the end
            }

            // this way we can avoid calling prepareToYield() every time (expensive)
            // as well as some other nuances handled
            cc->setDoingDeletes( true );

            DiskLoc rloc = cc->currLoc();
            BSONObj key = cc->currKey();

            bool match = creal->currentMatches();

            cc->advance();
            
            if ( ! match )
                continue;

            // SERVER-5198 Advance past the document to be modified, but see SERVER-5725.
            while( cc->ok() && rloc == cc->currLoc() ) {
                cc->advance();
            }
            
            bool foundAllResults = ( justOne || !cc->ok() );

            if ( !foundAllResults ) {
                // NOTE: Saving and restoring a btree cursor's position was historically described
                // as slow here.
                cc->c()->prepareToTouchEarlierIterate();
            }

            if ( logop ) {
                BSONElement e;
                if( BSONObj::make( rloc.rec() ).getObjectID( e ) ) {
                    BSONObjBuilder b;
                    b.append( e );
                    bool replJustOne = true;
                    logOp( "d", ns, b.done(), 0, &replJustOne );
                }
                else {
                    problem() << "deleted object without id, not logging" << endl;
                }
            }

            if ( rs )
                rs->goingToDelete( rloc.obj() /*cc->c->current()*/ );

            theDataFileMgr.deleteRecord(ns, rloc.rec(), rloc);
            nDeleted++;
            if ( foundAllResults ) {
                break;
            }
            cc->c()->recoverFromTouchingEarlierIterate();
         
            if( !god ) 
                getDur().commitIfNeeded();

            if( debug && god && nDeleted == 100 ) 
                log() << "warning high number of deletes with god=true which could use significant memory" << endl;
        }
        while ( cc->ok() );

        if ( cc.get() && ClientCursor::find( id , false ) == 0 ) {
            // TODO: remove this and the id declaration above if this doesn't trigger
            //       if it does, then i'm very confused (ERH 06/2011)
            error() << "this should be impossible" << endl;
            printStackTrace();
            cc.release();
        }

        return nDeleted;
    }

}
