gistcursor.cpp

此文件包含了在linux下实现tpr-tree索引的源代码

//--------------------------------------------------------------------
//        GiSTcursor.cpp
//        --------------
//
//        GiST - Generalized Search Tree 
//        June 2001 release, Aalborg University
//        
//        This file is a revised version of a part of the original 
//        libGiST release (version  0.9beta1)     
//        Copyright (c) 1996, Regents of the University of California
//

#include "GiST.h"

//------------------------------------------------
//   GiSTcursor
//

GiSTcursor::GiSTcursor(const GiST& gist,
		       const GiSTpredicate& query) : gist(gist)
{
    this->query = (GiSTpredicate*) query.Copy();
    first = 1;
    lastlevel = -1;
}

//------------------------------------------------
GiSTentry*
GiSTcursor::Next()
{
    GiSTpage page;

    while (first || !stack.IsEmpty())
    {
        if (first)
        {
            page = GiSTRootPage;
            first = 0;
        }
        else
        {
            assert(lastlevel >= 0);
            GiSTentry *entry = stack.RemoveFront();
            if (entry->IsLeaf()) return entry;

            // Pop off the stack
            for (int i=0; i < entry->Level() - lastlevel; i++)
               path.MakeParent();

            page = entry->Ptr();

            delete entry;
        }

        // Entry was a pointer to another node
        path.MakeChild(page);

        GiSTnode *node = gist.ReadNode(path);
        lastlevel = node->Level();
        GiSTlist<GiSTentry*> list = node->Search(*query);

        while (!list.IsEmpty())
        {
            GiSTentry *entry = list.RemoveRear();
            stack.Prepend(entry);
        }

        delete node;
    }

    // The search is over...
    return NULL;
}

//------------------------------------------------
GiSTcursor::~GiSTcursor()
{
    Flush();
    if (query != NULL) delete query;
}

//------------------------------------------------
const GiSTpath&
GiSTcursor::Path() const
{
    return path;
}

//------------------------------------------------
//   Ends search
void
GiSTcursor::Flush() 
{
   first = 0;
   while (!stack.IsEmpty()) delete stack.RemoveFront();   
}

//------------------------------------------------
//   GiSTdebugCursor
//

GiSTentry* GiSTdebugCursor::Next()
{
   GiSTentry* entry = NULL;
   
   do
   {
      if (entry) delete entry; 
      entry = GiSTcursor::Next();   
      if (!entry) return NULL;
   } while (!realQuery->Consistent(*entry));
   
   return entry;
}