SQLite4  Check-in [09251cee6a]

typedef struct LsmString LsmString;
typedef struct Mempool Mempool;
typedef struct Merge Merge;
typedef struct MergeInput MergeInput;
typedef struct MetaPage MetaPage;
typedef struct MultiCursor MultiCursor;
typedef struct Page Page;
typedef struct Redirect Redirect;
typedef struct Segment Segment;
typedef struct SegmentMerger SegmentMerger;
typedef struct ShmChunk ShmChunk;
typedef struct ShmHeader ShmHeader;
typedef struct ShmReader ShmReader;
typedef struct Snapshot Snapshot;
typedef struct TransMark TransMark;

/*
** Hard limit on the number of free-list entries that may be stored in 
** a checkpoint (the remainder are stored as a system record in the LSM).
** See also LSM_CONFIG_MAX_FREELIST.
*/
#define LSM_MAX_FREELIST_ENTRIES 24

#define LSM_MAX_BLOCK_REDIRECTS 16

#define LSM_ATTEMPTS_BEFORE_PROTOCOL 10000


/*
** Each entry stored in the LSM (or in-memory tree structure) has an
** associated mask of the following flags.

*/
typedef struct IntArray IntArray;
struct IntArray {
  int nAlloc;
  int nArray;
  u32 *aArray;
};

struct Redirect {
  int n;                          /* Number of redirects */
  struct RedirectEntry {
    int iFrom;
    int iTo;
  } *a;
};

/*
** An instance of this structure represents a point in the history of the
** tree structure to roll back to. Refer to comments in lsm_tree.c for 
** details.
*/
struct TreeMark {

};

struct Segment {
  Pgno iFirst;                     /* First page of this run */
  Pgno iLastPg;                    /* Last page of this run */
  Pgno iRoot;                      /* Root page number (if any) */
  int nSize;                       /* Size of this run in pages */

  Redirect *pRedirect;             /* Block redirects (or NULL) */
};

/*
** iSplitTopic/pSplitKey/nSplitKey:
**   If nRight>0, this buffer contains a copy of the largest key that has
**   already been written to the left-hand-side of the level.
*/

** Database below for futher details.
*/
struct Snapshot {
  Database *pDatabase;            /* Database this snapshot belongs to */
  Level *pLevel;                  /* Pointer to level 0 of snapshot (or NULL) */
  i64 iId;                        /* Snapshot id */
  i64 iLogOff;                    /* Log file offset */
  Redirect redirect;              /* Block redirection array */

  /* Used by worker snapshots only */
  int nBlock;                     /* Number of blocks in database file */
  Pgno aiAppend[LSM_APPLIST_SZ];  /* Append point list */
  Freelist freelist;              /* Free block list */
  u32 nWrite;                     /* Total number of pages written to disk */
};

int lsmFsSectorSize(FileSystem *);

void lsmSortedSplitkey(lsm_db *, Level *, int *);

/* Reading sorted run content. */
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg);
int lsmFsDbPageGet(FileSystem *, Segment *, Pgno, Page **);
int lsmFsDbPageNext(Segment *, Page *, int eDir, Page **);

u8 *lsmFsPageData(Page *, int *);
int lsmFsPageRelease(Page *);
int lsmFsPagePersist(Page *);
void lsmFsPageRef(Page *);
Pgno lsmFsPageNumber(Page *);

**     6. For each segment in the merge:
**        5a. Page number of next cell to read during merge (this field
**            is 64-bits - 2 integers)
**        5b. Cell number of next cell to read during merge
**     7. Page containing current split-key (64-bits - 2 integers).
**     8. Cell within page containing current split-key.
**     9. Current pointer value (64-bits - 2 integers).
**
**   The block redirect array:
**
**     1. Number of redirections (maximum LSM_MAX_BLOCK_REDIRECTS).
**     2. For each redirection:
**        a. "from" block number
**        b. "to" block number
**
**   The in-memory freelist entries. Each entry is either an insert or a
**   delete. The in-memory freelist is to the free-block-list as the
**   in-memory tree is to the users database content.
**
**     1. Number of free-list entries stored in checkpoint header.
**     2. Number of free blocks (in total).

  /* Serialize nLevel levels. */
  iLevel = 0;
  for(pLevel=lsmDbSnapshotLevel(pSnap); iLevel<nLevel; pLevel=pLevel->pNext){
    ckptExportLevel(pLevel, &ckpt, &iOut, &rc);
    iLevel++;
  }

  /* Write the block-redirect list */
  ckptSetValue(&ckpt, iOut++, pSnap->redirect.n, &rc);
  for(i=0; i<pSnap->redirect.n; &rc){
    ckptSetValue(&ckpt, iOut++, pSnap->redirect.a[i].iFrom, &rc);
    ckptSetValue(&ckpt, iOut++, pSnap->redirect.a[i].iTo, &rc);
  }

  /* Write the freelist */
  assert( pSnap->freelist.nEntry<=pDb->nMaxFreelist );
  if( rc==LSM_OK ){
    int nFree = pSnap->freelist.nEntry;
    ckptSetValue(&ckpt, iOut++, nFree, &rc);
    for(i=0; i<nFree; i++){

  Snapshot **ppSnap
){
  int rc = LSM_OK;
  Snapshot *pNew;

  pNew = (Snapshot *)lsmMallocZeroRc(pDb->pEnv, sizeof(Snapshot), &rc);
  if( rc==LSM_OK ){
    Level *pLvl;
    int nFree;
    int i;
    int nLevel = (int)aCkpt[CKPT_HDR_NLEVEL];
    int iIn = CKPT_HDR_SIZE + CKPT_APPENDLIST_SIZE + CKPT_LOGPTR_SIZE;

    pNew->iId = lsmCheckpointId(aCkpt, 0);
    pNew->nBlock = aCkpt[CKPT_HDR_NBLOCK];
    pNew->nWrite = aCkpt[CKPT_HDR_NWRITE];
    rc = ckptLoadLevels(pDb, aCkpt, &iIn, nLevel, &pNew->pLevel);
    pNew->iLogOff = lsmCheckpointLogOffset(aCkpt);

    /* Make a copy of the append-list */
    for(i=0; i<LSM_APPLIST_SZ; i++){
      u32 *a = &aCkpt[CKPT_HDR_SIZE + CKPT_LOGPTR_SIZE + i*2];
      pNew->aiAppend[i] = ckptRead64(a);
    }

    /* Read the block-redirect list */
    pNew->redirect.n = aCkpt[iIn++];
    if( pNew->redirect.n ){
      pNew->redirect.a = lsmMallocZeroRc(
          pDb->pEnv, (sizeof(struct RedirectEntry) * pNew->redirect.n), &rc
      );
      if( rc==LSM_OK ){
        for(i=0; i<pNew->redirect.n; i++){
          pNew->redirect.a[i].iFrom = aCkpt[iIn++];
          pNew->redirect.a[i].iTo = aCkpt[iIn++];
        }
      }
      for(pLvl=pNew->pLevel; pLvl->pNext; pLvl=pLvl->pNext);
      if( pLvl->nRight ){
        pLvl->aRhs[pLvl->nRight-1].pRedirect = &pNew->redirect;
      }else{
        pLvl->lhs.pRedirect = &pNew->redirect;
      }
    }

    /* Copy the free-list */
    if( rc==LSM_OK && bInclFreelist ){
      nFree = aCkpt[iIn++];
      if( nFree ){
        pNew->freelist.aEntry = (FreelistEntry *)lsmMallocZeroRc(
            pDb->pEnv, sizeof(FreelistEntry)*nFree, &rc
        );
        if( rc==LSM_OK ){
          int i;

    i64 nMin = (i64)nBlock * (i64)pFS->nBlocksize;
    fsGrowMapping(pFS, nMin, &rc);
    if( rc!=LSM_OK ) return rc;
  }
  return lsmEnvSync(pFS->pEnv, pFS->fdDb);
}

static int fsPageGet(FileSystem *, Redirect *, Pgno, int, Page **, int *);

/*
** Parameter iBlock is a database file block. This function reads the value 
** stored in the blocks "next block" pointer and stores it in *piNext.
** LSM_OK is returned if everything is successful, or an LSM error code
** otherwise.
*/

    rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aNext, sizeof(aNext));
    if( rc==LSM_OK ){
      *piNext = (int)lsmGetU32(aNext);
    }
  }else{
    const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
    Page *pLast;
    rc = fsPageGet(pFS, 0, iBlock*nPagePerBlock, 0, &pLast, 0);
    if( rc==LSM_OK ){
      *piNext = lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
      lsmFsPageRelease(pLast);
    }
  }
  return rc;
}

}

/*
** Return a handle for a database page.
*/
static int fsPageGet(
  FileSystem *pFS,                /* File-system handle */
  Redirect *pRedirect,            /* Block redirection to use (or NULL) */
  Pgno iPg,                       /* Page id */
  int noContent,                  /* True to not load content from disk */
  Page **ppPg,                    /* OUT: New page handle */
  int *pnSpace                    /* OUT: Bytes of free space */
){
  Page *p;
  int iHash;
  int rc = LSM_OK;

  /* In most cases iReal is the same as iPg. Except, if pRedirect is not
  ** NULL, and the block containing iPg has been redirected, then iReal
  ** is the page number after redirection.  */
  Pgno iReal = iPg;
  if( pRedirect ){
    const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
    int iBlk = fsPageToBlock(pFS, iPg);
    int i;
    for(i=0; i<pRedirect->n; i++){
      int iFrom = pRedirect->a[i].iFrom;
      if( iFrom>iBlk ) break;
      if( iFrom==iBlk ){
        int iTo = pRedirect->a[i].iTo;
        iReal = iPg - (Pgno)(iFrom - iTo) * nPagePerBlock;
        if( iTo==1 ){
          iReal += (fsFirstPageOnBlock(pFS, 1)-1);
        }
        break;
      }
    }
  }

  assert( iPg>=fsFirstPageOnBlock(pFS, 1) );
  assert( iReal>=fsFirstPageOnBlock(pFS, 1) );
  *ppPg = 0;

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->bUseMmap ){
    Page *pTest;
    i64 iEnd = (i64)iReal * pFS->nPagesize;
    fsGrowMapping(pFS, iEnd, &rc);
    if( rc!=LSM_OK ) return rc;

    p = 0;
    for(pTest=pFS->pWaiting; pTest; pTest=pTest->pNextWaiting){
      if( pTest->iPg==iReal ){
        assert( iReal==iPg );
        p = pTest;
        p->nRef++;
        *ppPg = p;
        return LSM_OK;
      }
    }
    if( pFS->pFree ){
      p = pFS->pFree;
      pFS->pFree = p->pHashNext;
      assert( p->nRef==0 );
    }else{
      p = lsmMallocZeroRc(pFS->pEnv, sizeof(Page), &rc);
      if( rc ) return rc;
      fsPageAddToLru(pFS, p);
      p->pFS = pFS;
    }
    p->aData = &((u8 *)pFS->pMap)[pFS->nPagesize * (iReal-1)];
    p->iPg = iReal;
  }else{

    /* Search the hash-table for the page */
    iHash = fsHashKey(pFS->nHash, iReal);
    for(p=pFS->apHash[iHash]; p; p=p->pHashNext){
      if( p->iPg==iReal) break;
    }

    if( p==0 ){
      rc = fsPageBuffer(pFS, 1, &p);
      if( rc==LSM_OK ){
        int nSpace = 0;
        p->iPg = iReal;
        p->nRef = 0;
        p->pFS = pFS;
        assert( p->flags==0 || p->flags==PAGE_FREE );

#ifdef LSM_DEBUG
        memset(p->aData, 0x56, pFS->nPagesize);
#endif
        assert( p->pLruNext==0 && p->pLruPrev==0 );
        if( noContent==0 ){
          if( pFS->pCompress ){
            rc = fsReadPagedata(pFS, p, &nSpace);
          }else{
            int nByte = pFS->nPagesize;
            i64 iOff = (i64)(iReal-1) * pFS->nPagesize;
            rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, p->aData, nByte);
          }
          pFS->nRead++;
        }

        /* If the xRead() call was successful (or not attempted), link the
         ** page into the page-cache hash-table. Otherwise, if it failed,

    assert( (rc==LSM_OK && (p || (pnSpace && *pnSpace)))
         || (rc!=LSM_OK && p==0) 
    );
  }

  if( rc==LSM_OK && p ){
    if( pFS->pCompress==0 && (fsIsLast(pFS, iReal) || fsIsFirst(pFS, iReal)) ){
      p->nData = pFS->nPagesize - 4;
      if( fsIsFirst(pFS, iReal) && p->nRef==0 ){
        p->aData += 4;
        p->flags |= PAGE_HASPREV;
      }
    }else{
      p->nData = pFS->nPagesize;
    }
    pFS->nOut += (p->nRef==0);

        }else{
          rc = fsGetPageBefore(pFS, iPg, &iPg);
        }
      }

      nSpace = 0;
      if( iPg!=0 ){
        rc = fsPageGet(pFS, pRun->pRedirect, iPg, 0, ppNext, &nSpace);
        assert( (*ppNext==0)==(rc!=LSM_OK || nSpace>0) );
      }else{
        *ppNext = 0;
      }
    }while( nSpace>0 && rc==LSM_OK );

  }else{

        return LSM_OK;
      }else if( fsIsLast(pFS, iPg) ){
        iPg = fsFirstPageOnBlock(pFS, lsmGetU32(&pPg->aData[pFS->nPagesize-4]));
      }else{
        iPg++;
      }
    }
    rc = fsPageGet(pFS, pRun->pRedirect, iPg, 0, ppNext, 0);
  }

  return rc;
}

static Pgno findAppendPoint(FileSystem *pFS, Level *pLvl){
  int i;

      }else{
        iNext = fsFirstPageOnBlock(pFS, iNew);
      }
    }

    /* Grab the new page. */
    pPg = 0;
    rc = fsPageGet(pFS, 0, iApp, 1, &pPg, 0);
    assert( rc==LSM_OK || pPg==0 );

    /* If this is the first or last page of a block, fill in the pointer 
     ** value at the end of the new page. */
    if( rc==LSM_OK ){
      p->nSize++;
      p->iLastPg = iApp;

/*
** Mark the sorted run passed as the second argument as finished. 
*/
int lsmFsSortedFinish(FileSystem *pFS, Segment *p){
  int rc = LSM_OK;
  if( p && p->iLastPg ){
    assert( p->pRedirect==0 );

    /* Check if the last page of this run happens to be the last of a block.
    ** If it is, then an extra block has already been allocated for this run.
    ** Shift this extra block back to the free-block list. 
    **
    ** Otherwise, add the first free page in the last block used by the run
    ** to the lAppend list.
    */
    if( fsLastPageOnPagesBlock(pFS, p->iLastPg)!=p->iLastPg ){
      int i;
      Pgno *aiAppend = pFS->pDb->pWorker->aiAppend;
      for(i=0; i<LSM_APPLIST_SZ; i++){
        if( aiAppend[i]==0 ){
          aiAppend[i] = p->iLastPg+1;
          break;
        }
      }
    }else if( pFS->pCompress==0 ){
      Page *pLast;
      rc = fsPageGet(pFS, 0, p->iLastPg, 0, &pLast, 0);
      if( rc==LSM_OK ){
        int iBlk = (int)lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
        lsmBlockRefree(pFS->pDb, iBlk);
        lsmFsPageRelease(pLast);
      }
    }else{
      int iBlk = 0;
      rc = fsBlockNext(pFS, fsPageToBlock(pFS, p->iLastPg), &iBlk);
      if( rc==LSM_OK ){
        lsmBlockRefree(pFS->pDb, iBlk);
      }
    }
  }
  return rc;
}

/*
** Obtain a reference to page number iPg.
*/
int lsmFsDbPageGet(FileSystem *pFS, Segment *pSeg, Pgno iPg, Page **ppPg){
  assert( pFS );
  assert( pSeg );
  return fsPageGet(pFS, pSeg->pRedirect, iPg, 0, ppPg, 0);
}

/*
** Obtain a reference to the last page in the segment passed as the 
** second argument.
*/
int lsmFsDbPageLast(FileSystem *pFS, Segment *pSeg, Page **ppPg){
  int rc;
  Pgno iPg = pSeg->iLastPg;
  if( pFS->pCompress ){
    int nSpace;
    iPg++;
    do {
      nSpace = 0;
      rc = fsGetPageBefore(pFS, iPg, &iPg);
      if( rc==LSM_OK ){
        rc = fsPageGet(pFS, pSeg->pRedirect, iPg, 0, ppPg, &nSpace);
      }
    }while( rc==LSM_OK && nSpace>0 );

  }else{
    rc = fsPageGet(pFS, pSeg->pRedirect, iPg, 0, ppPg, 0);
  }
  return rc;
}

/*
** Return a reference to meta-page iPg. If successful, LSM_OK is returned
** and *ppPg populated with the new page reference. The reference should

** eventually free the string using lsmFree().
**
** If an error occurs, *pzOut is set to NULL and an LSM error code returned.
*/
int lsmInfoArrayPages(lsm_db *pDb, Pgno iFirst, char **pzOut){
  int rc = LSM_OK;
  Snapshot *pWorker;              /* Worker snapshot */
  Segment *pSeg = 0;              /* Array to report on */
  int bUnlock = 0;

  *pzOut = 0;
  if( iFirst==0 ) return LSM_ERROR;

  /* Obtain the worker snapshot */
  pWorker = pDb->pWorker;
  if( !pWorker ){
    rc = lsmBeginWork(pDb);
    if( rc!=LSM_OK ) return rc;
    pWorker = pDb->pWorker;
    bUnlock = 1;
  }

  /* Search for the array that starts on page iFirst */
  pSeg = findSegment(pWorker, iFirst);

  if( pSeg==0 ){
    /* Could not find the requested array. This is an error. */
    rc = LSM_ERROR;
  }else{
    Page *pPg = 0;
    FileSystem *pFS = pDb->pFS;
    LsmString str;

    lsmStringInit(&str, pDb->pEnv);
    rc = lsmFsDbPageGet(pFS, pSeg, iFirst, &pPg);
    while( rc==LSM_OK && pPg ){
      Page *pNext = 0;
      lsmStringAppendf(&str, " %lld", lsmFsPageNumber(pPg));
      rc = lsmFsDbPageNext(pSeg, pPg, 1, &pNext);
      lsmFsPageRelease(pPg);
      pPg = pNext;
    }

    if( rc!=LSM_OK ){
      lsmFree(pDb->pEnv, str.z);
    }else{

  return rc;
}

void lsmFreeSnapshot(lsm_env *pEnv, Snapshot *p){
  if( p ){
    lsmSortedFreeLevel(pEnv, p->pLevel);
    lsmFree(pEnv, p->freelist.aEntry);
    lsmFree(pEnv, p->redirect.a);
    lsmFree(pEnv, p);
  }
}

/*
** Argument bFlush is true if the contents of the in-memory tree has just
** been flushed to disk. The significance of this is that once the snapshot

static void sortedBlobFree(Blob *pBlob){
  assert( pBlob->pEnv || pBlob->pData==0 );
  if( pBlob->pData ) lsmFree(pBlob->pEnv, pBlob->pData);
  memset(pBlob, 0, sizeof(Blob));
}

static int sortedReadData(
  Segment *pSeg,
  Page *pPg,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  int rc = LSM_OK;

      assert( nRem>=0 );
      if( nRem==0 ) break;
      i -= iEnd;

      /* Grab the next page in the segment */

      do {
        rc = lsmFsDbPageNext(pSeg, pPg, 1, &pNext);
        if( rc==LSM_OK && pNext==0 ){
          rc = LSM_CORRUPT_BKPT;
        }
        if( rc ) break;
        lsmFsPageRelease(pPg);
        pPg = pNext;
        aData = fsPageData(pPg, &nData);

  assert( iCell<pageGetNRec(aData, nData) && iCell>=0 );
  aCell = pageGetCell(aData, nData, iCell);
  lsmVarintGet64(&aCell[1], &iRet);
  return iRet;
}

static u8 *pageGetKey(
  Segment *pSeg,                  /* Segment pPg belongs to */
  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  int *pnKey,                     /* OUT: Size of key in bytes */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  u8 *pKey;

  pKey += lsmVarintGet32(pKey, &nDummy);
  pKey += lsmVarintGet32(pKey, pnKey);
  if( rtIsWrite(eType) ){
    pKey += lsmVarintGet32(pKey, &nDummy);
  }
  *piTopic = rtTopic(eType);

  sortedReadData(pSeg, pPg, pKey-aData, *pnKey, (void **)&pKey, pBlob);
  return pKey;
}

static int pageGetKeyCopy(
  lsm_env *pEnv,                  /* Environment handle */
  Segment *pSeg,                  /* Segment pPg belongs to */
  Page *pPg,                      /* Page to read from */
  int iCell,                      /* Index of cell on page to read */
  int *piTopic,                   /* OUT: Topic associated with this key */
  Blob *pBlob                     /* If required, use this for dynamic memory */
){
  int rc = LSM_OK;
  int nKey;
  u8 *aKey;

  aKey = pageGetKey(pSeg, pPg, iCell, piTopic, &nKey, pBlob);
  assert( (void *)aKey!=pBlob->pData || nKey==pBlob->nData );
  if( (void *)aKey!=pBlob->pData ){
    rc = sortedBlobSet(pEnv, pBlob, aKey, nKey);
  }

  return rc;
}

  return iRef;
}

#define GETVARINT64(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet64((a), &(i)))
#define GETVARINT32(a, i) (((i)=((u8*)(a))[0])<=240?1:lsmVarintGet32((a), &(i)))

static int pageGetBtreeKey(
  Segment *pSeg,                  /* Segment page pPg belongs to */
  Page *pPg,
  int iKey, 
  Pgno *piPtr, 
  int *piTopic, 
  void **ppKey,
  int *pnKey,
  Blob *pBlob

  aCell += GETVARINT64(aCell, *piPtr);

  if( eType==0 ){
    int rc;
    Pgno iRef;                  /* Page number of referenced page */
    Page *pRef;
    aCell += GETVARINT64(aCell, iRef);
    rc = lsmFsDbPageGet(lsmPageFS(pPg), pSeg, iRef, &pRef);
    if( rc!=LSM_OK ) return rc;
    pageGetKeyCopy(lsmPageEnv(pPg), pSeg, pRef, 0, &eType, pBlob);
    lsmFsPageRelease(pRef);
    *ppKey = pBlob->pData;
    *pnKey = pBlob->nData;
  }else{
    aCell += GETVARINT32(aCell, *pnKey);
    *ppKey = aCell;
  }

    int iCell = pCsr->aPg[iPg].iCell;
    while( iCell<0 && (--iPg)>=0 ){
      iCell = pCsr->aPg[iPg].iCell-1;
    }
    if( iPg<0 || iCell<0 ) return LSM_CORRUPT_BKPT;

    rc = pageGetBtreeKey(
        pCsr->pSeg,
        pCsr->aPg[iPg].pPage, iCell,
        &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
    );
    pCsr->eType |= LSM_SEPARATOR;
  }

  return rc;

    if( pCsr->iPg>=0 ){
      pCsr->aPg[pCsr->iPg].iCell++;

      iLoad = btreeCursorPtr(aData, nData, pPg->iCell);
      do {
        Page *pLoad;
        pCsr->iPg++;
        rc = lsmFsDbPageGet(pCsr->pFS, pCsr->pSeg, iLoad, &pLoad);
        pCsr->aPg[pCsr->iPg].pPage = pLoad;
        pCsr->aPg[pCsr->iPg].iCell = 0;
        if( rc==LSM_OK ){
          if( pCsr->iPg==(pCsr->nDepth-1) ) break;
          aData = fsPageData(pLoad, &nData);
          iLoad = btreeCursorPtr(aData, nData, 0);
        }

  int rc;

  Page *pPg = 0;
  FileSystem *pFS = pCsr->pFS;
  int iPg = pCsr->pSeg->iRoot;

  do {
    rc = lsmFsDbPageGet(pFS, pCsr->pSeg, iPg, &pPg);
    assert( (rc==LSM_OK)==(pPg!=0) );
    if( rc==LSM_OK ){
      u8 *aData;
      int nData;
      int flags;

      aData = fsPageData(pPg, &nData);

    /* Allocate the BtreeCursor.aPg[] array */
    assert( pCsr->aPg==0 );
    pCsr->aPg = (BtreePg *)lsmMallocZeroRc(pEnv, sizeof(BtreePg) * nDepth, &rc);

    /* Populate the last entry of the aPg[] array */
    if( rc==LSM_OK ){
      Page **pp = &pCsr->aPg[nDepth-1].pPage;
      pCsr->iPg = nDepth-1;
      pCsr->nDepth = nDepth;
      pCsr->aPg[pCsr->iPg].iCell = iCell;
      rc = lsmFsDbPageGet(pCsr->pFS, pCsr->pSeg, iLeaf, pp);
    }

    /* Populate any other aPg[] array entries */
    if( rc==LSM_OK && nDepth>1 ){
      Blob blob = {0,0,0};
      void *pSeek;
      int nSeek;

        ** greater than any real key.  */
        assert( iCell==-1 );
        iTopicSeek = 1000;
        pSeek = 0;
        nSeek = 0;
      }else{
        Pgno dummy;
        rc = pageGetBtreeKey(pCsr->pSeg, pPg,
            0, &dummy, &iTopicSeek, &pSeek, &nSeek, &pCsr->blob
        );
      }

      do {
        Page *pPg;
        rc = lsmFsDbPageGet(pCsr->pFS, pCsr->pSeg, iLoad, &pPg);
        assert( rc==LSM_OK || pPg==0 );
        if( rc==LSM_OK ){
          u8 *aData;                  /* Buffer containing page data */
          int nData;                  /* Size of aData[] in bytes */
          int iMin;
          int iMax;
          int iCell;

          while( iMax>=iMin ){
            int iTry = (iMin+iMax)/2;
            void *pKey; int nKey;         /* Key for cell iTry */
            int iTopic;                   /* Topic for key pKeyT/nKeyT */
            Pgno iPtr;                    /* Pointer for cell iTry */
            int res;                      /* (pSeek - pKeyT) */

            rc = pageGetBtreeKey(
                pCsr->pSeg, pPg, iTry, &iPtr, &iTopic, &pKey, &nKey, &blob
            );
            if( rc!=LSM_OK ) break;

            res = sortedKeyCompare(
                xCmp, iTopicSeek, pSeek, nSeek, iTopic, pKey, nKey
            );
            assert( res!=0 );

      if( pBtreePg->iCell<0 ){
        Pgno dummy;
        int i;
        for(i=pCsr->iPg-1; i>=0; i--){
          if( pCsr->aPg[i].iCell>0 ) break;
        }
        assert( i>=0 );
        rc = pageGetBtreeKey(pCsr->pSeg,
            pCsr->aPg[i].pPage, pCsr->aPg[i].iCell-1,
            &dummy, &pCsr->eType, &pCsr->pKey, &pCsr->nKey, &pCsr->blob
        );
        pCsr->eType |= LSM_SEPARATOR;

      }else{
        rc = btreeCursorLoadKey(pCsr);

  FileSystem *pFS,
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int iNew                       /* Page number of new page */
){
  Page *pPg = 0;                 /* The new page */
  int rc;                        /* Return Code */

  rc = lsmFsDbPageGet(pFS, pPtr->pSeg, iNew, &pPg);
  assert( rc==LSM_OK || pPg==0 );
  segmentPtrSetPage(pPtr, pPg);

  return rc;
}

static int segmentPtrReadData(
  SegmentPtr *pPtr,
  int iOff,
  int nByte,
  void **ppData,
  Blob *pBlob
){
  return sortedReadData(pPtr->pSeg, pPtr->pPg, iOff, nByte, ppData, pBlob);
}

static int segmentPtrNextPage(
  SegmentPtr *pPtr,              /* Load page into this SegmentPtr object */
  int eDir                       /* +1 for next(), -1 for prev() */
){
  Page *pNext;                   /* New page to load */

      pPtr->pVal = 0;
    }
  }

  return rc;
}


static Segment *sortedSplitkeySegment(Level *pLevel){
  Merge *pMerge = pLevel->pMerge;
  MergeInput *p = &pMerge->splitkey;
  Segment *pSeg;
  int i;

  for(i=0; i<pMerge->nInput; i++){
    if( p->iPg==pMerge->aInput[i].iPg ) break;
  }
  if( pMerge->nInput==(pLevel->nRight+1) && i>=(pMerge->nInput-1) ){
    pSeg = &pLevel->pNext->lhs;
  }else{
    pSeg = &pLevel->aRhs[i];
  }

  return pSeg;
}

static void sortedSplitkey(lsm_db *pDb, Level *pLevel, int *pRc){
  Segment *pSeg;
  Page *pPg = 0;
  lsm_env *pEnv = pDb->pEnv;      /* Environment handle */
  int rc = *pRc;
  Merge *pMerge = pLevel->pMerge;

  pSeg = sortedSplitkeySegment(pLevel);
  if( rc==LSM_OK ){
    rc = lsmFsDbPageGet(pDb->pFS, pSeg, pMerge->splitkey.iPg, &pPg);
  }
  if( rc==LSM_OK ){
    int iTopic;
    Blob blob = {0, 0, 0, 0};
    u8 *aData;
    int nData;
  
    aData = lsmFsPageData(pPg, &nData);
    if( pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG ){
      void *pKey;
      int nKey;
      Pgno dummy;
      rc = pageGetBtreeKey(pSeg,
          pPg, pMerge->splitkey.iCell, &dummy, &iTopic, &pKey, &nKey, &blob
      );
      if( rc==LSM_OK && blob.pData!=pKey ){
        rc = sortedBlobSet(pEnv, &blob, pKey, nKey);
      }
    }else{
      rc = pageGetKeyCopy(
          pEnv, pSeg, pPg, pMerge->splitkey.iCell, &iTopic, &blob
      );
    }

    pLevel->iSplitTopic = iTopic;
    pLevel->pSplitKey = blob.pData;
    pLevel->nSplitKey = blob.nData;
    lsmFsPageRelease(pPg);
  }

      int res = sortedKeyCompare(pCsr->pDb->xCmp,
          rtTopic(pPtr->eType), pPtr->pKey, pPtr->nKey,
          pLvl->iSplitTopic, pLvl->pSplitKey, pLvl->nSplitKey
      );
      if( res<0 ) segmentPtrReset(pPtr);
    }
    if( pPtr->pPg==0 && (svFlags & LSM_END_DELETE) ){
      Segment *pSeg = pPtr->pSeg;
      rc = lsmFsDbPageGet(pCsr->pDb->pFS, pSeg, pSeg->iFirst, &pPtr->pPg);
      if( rc!=LSM_OK ) return rc;
      pPtr->eType = LSM_START_DELETE | (pLvl->iSplitTopic ? LSM_SYSTEMKEY : 0);
      pPtr->pKey = pLvl->pSplitKey;
      pPtr->nKey = pLvl->nSplitKey;
    }

  }while( pCsr 

static void segmentPtrEndPage(
  FileSystem *pFS, 
  SegmentPtr *pPtr, 
  int bLast, 
  int *pRc
){
  if( *pRc==LSM_OK ){
    Segment *pSeg = pPtr->pSeg;
    Page *pNew = 0;
    if( bLast ){
      *pRc = lsmFsDbPageLast(pFS, pSeg, &pNew);
    }else{
      *pRc = lsmFsDbPageGet(pFS, pSeg, pSeg->iFirst, &pNew);
    }
    segmentPtrSetPage(pPtr, pNew);
  }
}


/*

  int iTopic = 0;                 /* TODO: Fix me */

  for(eDir=-1; eDir<=1; eDir+=2){
    Page *pTest = pPtr->pPg;

    lsmFsPageRef(pTest);
    while( pTest ){
      Segment *pSeg = pPtr->pSeg;
      Page *pNext;

      int rc = lsmFsDbPageNext(pSeg, pTest, eDir, &pNext);
      lsmFsPageRelease(pTest);
      if( rc ) return 1;
      pTest = pNext;

      if( pTest ){
        int nData;
        u8 *aData = fsPageData(pTest, &nData);
        int nCell = pageGetNRec(aData, nData);
        int flags = pageGetFlags(aData, nData);
        if( nCell && 0==(flags&SEGMENT_BTREE_FLAG) ){
          int nPgKey;
          int iPgTopic;
          u8 *pPgKey;
          int res;
          int iCell;

          iCell = ((eDir < 0) ? (nCell-1) : 0);
          pPgKey = pageGetKey(pSeg, pTest, iCell, &iPgTopic, &nPgKey, &blob);
          res = iTopic - iPgTopic;
          if( res==0 ) res = pCsr->pDb->xCmp(pKey, nKey, pPgKey, nPgKey);
          if( (eDir==1 && res>0) || (eDir==-1 && res<0) ){
            /* Taking this branch means something has gone wrong. */
            char *zMsg = lsmMallocPrintf(pEnv, "Key \"%s\" is not on page %d", 
                keyToString(pEnv, pKey, nKey), lsmFsPageNumber(pPtr->pPg)
            );

    u8 *pLastKey;
    int nLastKey;
    int iLastTopic;
    int res;                      /* Result of comparison */
    Page *pNext;

    /* Load the last key on the current page. */
    pLastKey = pageGetKey(pPtr->pSeg,
        pPtr->pPg, pPtr->nCell-1, &iLastTopic, &nLastKey, &pPtr->blob1
    );

    /* If the loaded key is >= than (pKey/nKey), break out of the loop.
    ** If (pKey/nKey) is present in this array, it must be on the current 
    ** page.  */
    res = sortedKeyCompare(

  do {
    Pgno *piFirst = 0;
    if( aPg ){
      aPg[i++] = iPg;
      piFirst = &aPg[i];
    }

    rc = lsmFsDbPageGet(pCsr->pDb->pFS, pSeg, iPg, &pPg);
    assert( rc==LSM_OK || pPg==0 );
    if( rc==LSM_OK ){
      u8 *aData;                  /* Buffer containing page data */
      int nData;                  /* Size of aData[] in bytes */
      int iMin;
      int iMax;
      int nRec;

      while( iMax>=iMin ){
        int iTry = (iMin+iMax)/2;
        void *pKeyT; int nKeyT;       /* Key for cell iTry */
        int iTopicT;                  /* Topic for key pKeyT/nKeyT */
        Pgno iPtr;                    /* Pointer associated with cell iTry */
        int res;                      /* (pKey - pKeyT) */

        rc = pageGetBtreeKey(
            pSeg, pPg, iTry, &iPtr, &iTopicT, &pKeyT, &nKeyT, &blob
        );
        if( rc!=LSM_OK ) break;
        if( piFirst && pKeyT==blob.pData ){
          *piFirst = pageGetBtreeRef(pPg, iTry);
          piFirst = 0;
          i++;
        }

    for(i=0; i<pLvl->nRight; i++){
      pCsr->aPtr[iPtr].pLevel = pLvl;
      pCsr->aPtr[iPtr].pSeg = &pLvl->aRhs[i];
      iPtr++;
    }

    if( pLvl->nRight && pLvl->pSplitKey==0 ){
      sortedSplitkey(pCsr->pDb, pLvl, &rc);
    }
  }

  return rc;
}

static int multiCursorInit(MultiCursor *pCsr, Snapshot *pSnap){

    do {
      Page *pPg = 0;
      u8 *aData;
      int nData;
      int flags;

      rc = lsmFsDbPageGet(pFS, pSeg, iPg, &pPg);
      if( rc!=LSM_OK ) break;

      aData = fsPageData(pPg, &nData);
      flags = pageGetFlags(aData, nData);
      if( flags&SEGMENT_BTREE_FLAG ){
        Page **apNew = (Page **)lsmRealloc(
            pEnv, apHier, sizeof(Page *)*(nHier+1)

  if( pCsr->pBtCsr ){
    rc = LSM_OK;
    iFPtr = pMW->pLevel->pNext->lhs.iFirst;
  }else if( pCsr->nPtr>0 ){
    Segment *pSeg;
    pSeg = pCsr->aPtr[pCsr->nPtr-1].pSeg;
    rc = lsmFsDbPageGet(pMW->pDb->pFS, pSeg, pSeg->iFirst, &pPg);
    if( rc==LSM_OK ){
      u8 *aData;                    /* Buffer for page pPg */
      int nData;                    /* Size of aData[] in bytes */
      aData = fsPageData(pPg, &nData);
      iFPtr = pageGetPtr(aData, nData);
      lsmFsPageRelease(pPg);
    }

  if( pTop && pTop->iAge==0
   && (pTop->nRight || sortedCountLevels(pTop)>=pDb->nMerge)
  ){
    return 1;
  }
  return 0;
}

static int sortedMoveBlocks(lsm_db *pDb, int *pnWrite){
  Level *pLvl = lsmDbSnapshotLevel(pDb->pWorker);
  assert( pLvl->pNext==0 && pLvl->nRight==0 );

  *pnWrite = 0;
  return LSM_OK;
}

static int sortedWork(
  lsm_db *pDb,                    /* Database handle. Must be worker. */
  int nWork,                      /* Number of pages of work to do */
  int nMerge,                     /* Try to merge this many levels at once */
  int bFlush,                     /* Set if call is to make room for a flush */
  int *pnWrite                    /* OUT: Actual number of pages written */

    Level *pLevel = 0;

    /* Find a level to work on. */
    rc = sortedSelectLevel(pDb, nMerge, &pLevel);
    assert( rc==LSM_OK || pLevel==0 );

    if( pLevel==0 ){
      int nDone = 0;
      Level *pTopLevel = lsmDbSnapshotLevel(pDb->pWorker);
      if( bFlush==0 && nMerge==1 && pTopLevel && pTopLevel->pNext==0 ){
        rc = sortedMoveBlocks(pDb, &nDone);
      }
      nRemaining -= nDone;

      /* Could not find any work to do. Finished. */
      if( nDone==0 ) break;
    }else{
      MergeWorker mergeworker;    /* State used to work on the level merge */

      rc = mergeWorkerInit(pDb, pLevel, &mergeworker);
      assert( mergeworker.nWork==0 );
      while( rc==LSM_OK 
          && 0==mergeWorkerDone(&mergeworker) 

    eType = *aCell++;
    assert( (flags & SEGMENT_BTREE_FLAG) || eType!=0 );
    aCell += lsmVarintGet32(aCell, &iPgPtr);

    if( eType==0 ){
      Pgno iRef;                  /* Page number of referenced page */
      aCell += lsmVarintGet64(aCell, &iRef);
      lsmFsDbPageGet(pDb->pFS, pRun, iRef, &pRef);
      aKey = pageGetKey(pRun, pRef, 0, &iTopic, &nKey, &blob);
    }else{
      aCell += lsmVarintGet32(aCell, &nKey);
      if( rtIsWrite(eType) ) aCell += lsmVarintGet32(aCell, &nVal);
      sortedReadData(0, pPg, (aCell-aData), nKey+nVal, (void **)&aKey, &blob);
      aVal = &aKey[nKey];
      iTopic = eType;
    }

    lsmStringAppendf(&s, "%s%2X:", (i==0?"":" "), iTopic);
    for(iChar=0; iChar<nKey; iChar++){
      lsmStringAppendf(&s, "%c", isalnum(aKey[iChar]) ? aKey[iChar] : '.');

  int iCell,
  int *peType,
  int *piPgPtr,
  u8 **paKey, int *pnKey,
  u8 **paVal, int *pnVal,
  Blob *pBlob
){
#if 0
  u8 *aData; int nData;           /* Page data */
  u8 *aKey; int nKey = 0;         /* Key */
  u8 *aVal; int nVal = 0;         /* Value */
  int eType;
  int iPgPtr;
  Page *pRef = 0;                 /* Pointer to page iRef */
  u8 *aCell;

  aData = fsPageData(pPg, &nData);

  aCell = pageGetCell(aData, nData, iCell);
  eType = *aCell++;
  aCell += lsmVarintGet32(aCell, &iPgPtr);

  if( eType==0 ){
    int dummy;
    Pgno iRef;                  /* Page number of referenced page */
    aCell += lsmVarintGet64(aCell, &iRef);
    if( bIndirect ){
      lsmFsDbPageGet(pDb->pFS, TODO, iRef, &pRef);
      pageGetKeyCopy(pDb->pEnv, pRef, 0, &dummy, pBlob);
      aKey = (u8 *)pBlob->pData;
      nKey = pBlob->nData;
      lsmFsPageRelease(pRef);
    }else{
      aKey = (u8 *)"<indirect>";
      nKey = 11;

  if( peType ) *peType = eType;
  if( piPgPtr ) *piPgPtr = iPgPtr;
  if( paKey ) *paKey = aKey;
  if( paVal ) *paVal = aVal;
  if( pnKey ) *pnKey = nKey;
  if( pnVal ) *pnVal = nVal;
#endif
}

static int infoAppendBlob(LsmString *pStr, int bHex, u8 *z, int n){
  int iChar;
  for(iChar=0; iChar<n; iChar++){
    if( bHex ){
      lsmStringAppendf(pStr, "%02X", z[iChar]);

static int infoPageDump(
  lsm_db *pDb,                    /* Database handle */
  Pgno iPg,                       /* Page number of page to dump */
  int flags,
  char **pzOut                    /* OUT: lsmMalloc'd string */
){
  int rc = LSM_OK;                /* Return code */
#if 0
  Page *pPg = 0;                  /* Handle for page iPg */
  int i, j;                       /* Loop counters */
  const int perLine = 16;         /* Bytes per line in the raw hex dump */

  int bValues = (flags & INFO_PAGE_DUMP_VALUES);
  int bHex = (flags & INFO_PAGE_DUMP_HEX);
  int bData = (flags & INFO_PAGE_DUMP_DATA);
  int bIndirect = (flags & INFO_PAGE_DUMP_INDIRECT);

  *pzOut = 0;
  if( iPg==0 ) return LSM_ERROR;

  rc = lsmFsDbPageGet(pDb->pFS, TODO, iPg, &pPg);
  if( rc==LSM_OK ){
    Blob blob = {0, 0, 0, 0};
    int nKeyWidth = 0;
    LsmString str;
    int nRec;
    int iPtr;
    int flags;

    }

    *pzOut = str.z;
    sortedBlobFree(&blob);
    lsmFsPageRelease(pPg);
  }

#endif
  return rc;
}

int lsmInfoPageDump(
  lsm_db *pDb,                    /* Database handle */
  Pgno iPg,                       /* Page number of page to dump */
  int bHex,                       /* True to output key/value in hex form */

    char *zSeg;
    Page *pPg;

    zSeg = segToString(pDb->pEnv, pRun, 0);
    lsmLogMessage(pDb, LSM_OK, "Segment: %s", zSeg);
    lsmFree(pDb->pEnv, zSeg);

    lsmFsDbPageGet(pDb->pFS, pRun, pRun->iFirst, &pPg);
    while( pPg ){
      Page *pNext;
      char *z = 0;
      infoPageDump(pDb, lsmFsPageNumber(pPg), flags, &z);
      lsmLogMessage(pDb, LSM_OK, "%s", z);
      lsmFree(pDb->pEnv, z);
#if 0

#ifdef LSM_DEBUG_EXPENSIVE
static void assertRunInOrder(lsm_db *pDb, Segment *pSeg){
  Page *pPg = 0;
  Blob blob1 = {0, 0, 0, 0};
  Blob blob2 = {0, 0, 0, 0};

  lsmFsDbPageGet(pDb->pFS, pSeg, pSeg->iFirst, &pPg);
  while( pPg ){
    u8 *aData; int nData;
    Page *pNext;

    aData = lsmFsPageData(pPg, &nData);
    if( 0==(pageGetFlags(aData, nData) & SEGMENT_BTREE_FLAG) ){
      int i;
      int nRec = pageGetNRec(aData, nData);
      for(i=0; i<nRec; i++){
        int iTopic1, iTopic2;
        pageGetKeyCopy(pDb->pEnv, pSeg, pPg, i, &iTopic1, &blob1);

        if( i==0 && blob2.nData ){
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic2, blob2.pData, blob2.nData,
                iTopic1, blob1.pData, blob1.nData
          )<0 );
        }

        if( i<(nRec-1) ){
          pageGetKeyCopy(pDb->pEnv, pSeg, pPg, i+1, &iTopic2, &blob2);
          assert( sortedKeyCompare(
                pDb->xCmp, iTopic1, blob1.pData, blob1.nData,
                iTopic2, blob2.pData, blob2.nData
          )<0 );
        }
      }
    }

    BtreeCursor *pCsr = 0;        /* Btree cursor */

    rc = btreeCursorNew(pDb, pSeg, &pCsr);
    if( rc==LSM_OK ){
      rc = btreeCursorFirst(pCsr);
    }
    if( rc==LSM_OK ){
      rc = lsmFsDbPageGet(pFS, pSeg, pSeg->iFirst, &pPg);
    }

    while( rc==LSM_OK ){
      Page *pNext;
      u8 *aData;
      int nData;
      int flags;

      if( rc==LSM_OK 
       && 0==((SEGMENT_BTREE_FLAG|PGFTR_SKIP_THIS_FLAG) & flags)
       && 0!=pageGetNRec(aData, nData)
      ){
        u8 *pKey;
        int nKey;
        int iTopic;
        pKey = pageGetKey(pSeg, pPg, 0, &iTopic, &nKey, &blob);
        assert( nKey==pCsr->nKey && 0==memcmp(pKey, pCsr->pKey, nKey) );
        assert( lsmFsPageNumber(pPg)==pCsr->iPtr );
        rc = btreeCursorNext(pCsr);
      }
    }
    assert( rc!=LSM_OK || pCsr->pKey==0 );