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Overview
Comment:Fix some bugs surrounding block redirects.
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Timelines: family | ancestors | descendants | both | block-redirects
Files: files | file ages | folders
SHA1: 73976dbcbe892e2a76b9c26b9cbbfc1b489ed626
User & Date: dan 2013-01-21 10:02:17.783
Context
2013-01-21
14:23
Fix LSM_INFO_PAGE_DUMP so that it works with redirected blocks. check-in: deb0ccacd4 user: dan tags: block-redirects
10:02
Fix some bugs surrounding block redirects. check-in: 73976dbcbe user: dan tags: block-redirects
2013-01-19
20:07
Change the lsm file-format to allow a small number of blocks belonging to the oldest segment in the database to be moved without modifying their content. This makes it easier to compact a database file to the minimum required size. check-in: 09251cee6a user: dan tags: block-redirects
Changes
Unified Diff Ignore Whitespace Patch
Changes to src/lsmInt.h.
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void lsmSnapshotSetCkptid(Snapshot *, i64);

Level *lsmDbSnapshotLevel(Snapshot *);
void lsmDbSnapshotSetLevel(Snapshot *, Level *);

void lsmDbRecoveryComplete(lsm_db *, int);

int lsmBlockAllocate(lsm_db *, int *);
int lsmBlockFree(lsm_db *, int);
int lsmBlockRefree(lsm_db *, int);

void lsmFreelistDeltaBegin(lsm_db *);
void lsmFreelistDeltaEnd(lsm_db *);
int lsmFreelistDelta(lsm_db *pDb);








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void lsmSnapshotSetCkptid(Snapshot *, i64);

Level *lsmDbSnapshotLevel(Snapshot *);
void lsmDbSnapshotSetLevel(Snapshot *, Level *);

void lsmDbRecoveryComplete(lsm_db *, int);

int lsmBlockAllocate(lsm_db *, int, int *);
int lsmBlockFree(lsm_db *, int);
int lsmBlockRefree(lsm_db *, int);

void lsmFreelistDeltaBegin(lsm_db *);
void lsmFreelistDeltaEnd(lsm_db *);
int lsmFreelistDelta(lsm_db *pDb);

Changes to src/lsm_ckpt.c.
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  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 ){







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  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; i++){
    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 ){
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      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++];
        }
      }







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      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) * LSM_MAX_BLOCK_REDIRECTS), &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++];
        }
      }
Changes to src/lsm_file.c.
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    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.
*/
static int fsBlockNext(
  FileSystem *pFS,                /* File-system object handle */

  int iBlock,                     /* Read field from this block */
  int *piNext                     /* OUT: Next block in linked list */
){
  int rc;








  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->pCompress ){
    i64 iOff;                     /* File offset to read data from */
    u8 aNext[4];                  /* 4-byte pointer read from db file */

    iOff = (i64)iBlock * pFS->nBlocksize - sizeof(aNext);
    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 the page number of the last page on the same block as page iPg.
*/
Pgno fsLastPageOnPagesBlock(FileSystem *pFS, Pgno iPg){







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    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 *);

static int fsRedirectBlock(Redirect *p, int iBlk){
  if( p ){
    int i;
    for(i=0; i<p->n; i++){
      if( iBlk==p->a[i].iFrom ) return p->a[i].iTo;
    }
  }
  return iBlk;
}

static Pgno fsRedirectPage(FileSystem *pFS, Redirect *pRedir, Pgno iPg){
  Pgno iReal = iPg;

  if( pRedir ){
    const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
    int iBlk = fsPageToBlock(pFS, iPg);
    int i;
    for(i=0; i<pRedir->n; i++){
      int iFrom = pRedir->a[i].iFrom;
      if( iFrom>iBlk ) break;
      if( iFrom==iBlk ){
        int iTo = pRedir->a[i].iTo;
        iReal = iPg - (Pgno)(iFrom - iTo) * nPagePerBlock;
        if( iTo==1 ){
          iReal += (fsFirstPageOnBlock(pFS, 1)-1);
        }
        break;
      }
    }
  }

  return iReal;
}

/*
** 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.
*/
static int fsBlockNext(
  FileSystem *pFS,                /* File-system object handle */
  Segment *pSeg,                  /* Use this segment for block redirects */
  int iBlock,                     /* Read field from this block */
  int *piNext                     /* OUT: Next block in linked list */
){
  int rc;
  int iRead;                      /* Read block from here */
  
  if( pSeg ){
    iRead = fsRedirectBlock(pSeg->pRedirect, iBlock);
  }else{
    iRead = iBlock;
  }

  assert( pFS->bUseMmap==0 || pFS->pCompress==0 );
  if( pFS->pCompress ){
    i64 iOff;                     /* File offset to read data from */
    u8 aNext[4];                  /* 4-byte pointer read from db file */

    iOff = (i64)iRead * pFS->nBlocksize - sizeof(aNext);
    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, iRead*nPagePerBlock, 0, &pLast, 0);
    if( rc==LSM_OK ){
      *piNext = lsmGetU32(&pLast->aData[pFS->nPagesize-4]);
      lsmFsPageRelease(pLast);
    }
  }

  if( pSeg ){
    *piNext = fsRedirectBlock(pSeg->pRedirect, *piNext);
  }
  return rc;
}

/*
** Return the page number of the last page on the same block as page iPg.
*/
Pgno fsLastPageOnPagesBlock(FileSystem *pFS, Pgno iPg){
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  iEob = fsLastPageOnPagesBlock(pFS, iOff) + 1;
  nRead = LSM_MIN(iEob - iOff, nData);

  rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aData, nRead);
  if( rc==LSM_OK && nRead!=nData ){
    int iBlk;



    rc = fsBlockNext(pFS, fsPageToBlock(pFS, iOff), &iBlk);
    if( rc==LSM_OK ){
      i64 iOff2 = fsFirstPageOnBlock(pFS, iBlk);
      rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff2, &aData[nRead], nData-nRead);
    }
  }

  return rc;







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  iEob = fsLastPageOnPagesBlock(pFS, iOff) + 1;
  nRead = LSM_MIN(iEob - iOff, nData);

  rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff, aData, nRead);
  if( rc==LSM_OK && nRead!=nData ){
    int iBlk;

    /* TODO: Fix the pSeg arg to this */
    assert( 0 );
    rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iOff), &iBlk);
    if( rc==LSM_OK ){
      i64 iOff2 = fsFirstPageOnBlock(pFS, iBlk);
      rc = lsmEnvRead(pFS->pEnv, pFS->fdDb, iOff2, &aData[nRead], nData-nRead);
    }
  }

  return rc;
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  iEob = fsLastPageOnPagesBlock(pFS, iOff);
  if( (iOff+iAdd)<=iEob ){
    *piRes = (iOff+iAdd);
    return LSM_OK;
  }


  rc = fsBlockNext(pFS, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsFirstPageOnBlock(pFS, iBlk) + iAdd - (iEob - iOff + 1);
  return rc;
}

static int fsAllocateBuffer(FileSystem *pFS, int bWrite){
  u8 **pp;                        /* Pointer to either aIBuffer or aOBuffer */








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  iEob = fsLastPageOnPagesBlock(pFS, iOff);
  if( (iOff+iAdd)<=iEob ){
    *piRes = (iOff+iAdd);
    return LSM_OK;
  }

  assert( 0 );
  rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iOff), &iBlk);
  *piRes = fsFirstPageOnBlock(pFS, iBlk) + iAdd - (iEob - iOff + 1);
  return rc;
}

static int fsAllocateBuffer(FileSystem *pFS, int bWrite){
  u8 **pp;                        /* Pointer to either aIBuffer or aOBuffer */

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    iBlk = fsPageToBlock(pFS, pDel->iFirst);
    iLastBlk = fsPageToBlock(pFS, pDel->iLastPg);

    /* Mark all blocks currently used by this sorted run as free */
    while( iBlk && rc==LSM_OK ){
      int iNext = 0;
      if( iBlk!=iLastBlk ){
        rc = fsBlockNext(pFS, iBlk, &iNext);
      }else if( bZero==0 && pDel->iLastPg!=fsLastPageOnBlock(pFS, iLastBlk) ){
        break;
      }
      rc = fsFreeBlock(pFS, pSnapshot, pDel, iBlk);
      iBlk = iNext;
    }








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    iBlk = fsPageToBlock(pFS, pDel->iFirst);
    iLastBlk = fsPageToBlock(pFS, pDel->iLastPg);

    /* Mark all blocks currently used by this sorted run as free */
    while( iBlk && rc==LSM_OK ){
      int iNext = 0;
      if( iBlk!=iLastBlk ){
        rc = fsBlockNext(pFS, pDel, iBlk, &iNext);
      }else if( bZero==0 && pDel->iLastPg!=fsLastPageOnBlock(pFS, iLastBlk) ){
        break;
      }
      rc = fsFreeBlock(pFS, pSnapshot, pDel, iBlk);
      iBlk = iNext;
    }

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  while( rc==LSM_OK ){
    int iNext = 0;
    Pgno iFirst = firstOnBlock(pFS, iBlk, aPgno, nPgno);
    if( iFirst ){
      pRun->iFirst = iFirst;
      break;
    }
    rc = fsBlockNext(pFS, iBlk, &iNext);
    if( rc==LSM_OK ) rc = fsFreeBlock(pFS, pSnapshot, pRun, iBlk);
    pRun->nSize -= (
        1 + fsLastPageOnBlock(pFS, iBlk) - fsFirstPageOnBlock(pFS, iBlk)
    );
    iBlk = iNext;
  }








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  while( rc==LSM_OK ){
    int iNext = 0;
    Pgno iFirst = firstOnBlock(pFS, iBlk, aPgno, nPgno);
    if( iFirst ){
      pRun->iFirst = iFirst;
      break;
    }
    rc = fsBlockNext(pFS, pRun, iBlk, &iNext);
    if( rc==LSM_OK ) rc = fsFreeBlock(pFS, pSnapshot, pRun, iBlk);
    pRun->nSize -= (
        1 + fsLastPageOnBlock(pFS, iBlk) - fsFirstPageOnBlock(pFS, iBlk)
    );
    iBlk = iNext;
  }

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  int rc = LSM_OK;
  FileSystem *pFS = pPg->pFS;
  Pgno iPg = pPg->iPg;

  if( pFS->pCompress ){
    int nSpace = pPg->nCompress + 2*3;




    do {
      if( eDir>0 ){
        rc = fsNextPageOffset(pFS, pRun, iPg, nSpace, &iPg);
      }else{
        if( iPg==pRun->iFirst ){
          iPg = 0;
        }else{







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  int rc = LSM_OK;
  FileSystem *pFS = pPg->pFS;
  Pgno iPg = pPg->iPg;

  if( pFS->pCompress ){
    int nSpace = pPg->nCompress + 2*3;

    /* TODO: Fix redirects */
    assert( 0 );

    do {
      if( eDir>0 ){
        rc = fsNextPageOffset(pFS, pRun, iPg, nSpace, &iPg);
      }else{
        if( iPg==pRun->iFirst ){
          iPg = 0;
        }else{
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      }else if( fsIsFirst(pFS, iPg) ){
        assert( pPg->flags & PAGE_HASPREV );
        iPg = fsLastPageOnBlock(pFS, lsmGetU32(&pPg->aData[-4]));
      }else{
        iPg--;
      }
    }else{

      if( pRun && iPg==pRun->iLastPg ){
        *ppNext = 0;
        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);
  }








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      }else if( fsIsFirst(pFS, iPg) ){
        assert( pPg->flags & PAGE_HASPREV );
        iPg = fsLastPageOnBlock(pFS, lsmGetU32(&pPg->aData[-4]));
      }else{
        iPg--;
      }
    }else{
      Pgno iLast = fsRedirectPage(pFS, pRun->pRedirect, pRun->iLastPg);
      if( pRun && iPg==iLast ){
        *ppNext = 0;
        return LSM_OK;
      }else if( fsIsLast(pFS, iPg) ){
        int iBlk = fsRedirectBlock(
            pRun->pRedirect, lsmGetU32(&pPg->aData[pFS->nPagesize-4])
        );
        iPg = fsFirstPageOnBlock(pFS, iBlk);
      }else{
        iPg++;
      }
    }
    rc = fsPageGet(pFS, pRun->pRedirect, iPg, 0, ppNext, 0);
  }

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  int rc = LSM_OK;
  Page *pPg = 0;
  *ppOut = 0;
  int iApp = 0;
  int iNext = 0;
  Segment *p = &pLvl->lhs;
  int iPrev = p->iLastPg;



  if( pFS->pCompress || bDefer ){
    /* In compressed database mode the page is not assigned a page number
    ** or location in the database file at this point. This will be done
    ** by the lsmFsPagePersist() call.  */
    rc = fsPageBuffer(pFS, 1, &pPg);
    if( rc==LSM_OK ){







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  int rc = LSM_OK;
  Page *pPg = 0;
  *ppOut = 0;
  int iApp = 0;
  int iNext = 0;
  Segment *p = &pLvl->lhs;
  int iPrev = p->iLastPg;

  assert( p->pRedirect==0 );

  if( pFS->pCompress || bDefer ){
    /* In compressed database mode the page is not assigned a page number
    ** or location in the database file at this point. This will be done
    ** by the lsmFsPagePersist() call.  */
    rc = fsPageBuffer(pFS, 1, &pPg);
    if( rc==LSM_OK ){
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      pFS->nOut++;
    }
  }else{
    if( iPrev==0 ){
      iApp = findAppendPoint(pFS, pLvl);
    }else if( fsIsLast(pFS, iPrev) ){
      int iNext;
      rc = fsBlockNext(pFS, fsPageToBlock(pFS, iPrev), &iNext);
      if( rc!=LSM_OK ) return rc;
      iApp = fsFirstPageOnBlock(pFS, iNext);
    }else{
      iApp = iPrev + 1;
    }

    /* If this is the first page allocated, or if the page allocated is the
    ** last in the block, also allocate the next block here.  */
    if( iApp==0 || fsIsLast(pFS, iApp) ){
      int iNew;                     /* New block number */

      rc = lsmBlockAllocate(pFS->pDb, &iNew);
      if( rc!=LSM_OK ) return rc;
      if( iApp==0 ){
        iApp = fsFirstPageOnBlock(pFS, iNew);
      }else{
        iNext = fsFirstPageOnBlock(pFS, iNew);
      }
    }







|











|







1694
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1708
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1714
1715
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      pFS->nOut++;
    }
  }else{
    if( iPrev==0 ){
      iApp = findAppendPoint(pFS, pLvl);
    }else if( fsIsLast(pFS, iPrev) ){
      int iNext;
      rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iPrev), &iNext);
      if( rc!=LSM_OK ) return rc;
      iApp = fsFirstPageOnBlock(pFS, iNext);
    }else{
      iApp = iPrev + 1;
    }

    /* If this is the first page allocated, or if the page allocated is the
    ** last in the block, also allocate the next block here.  */
    if( iApp==0 || fsIsLast(pFS, iApp) ){
      int iNew;                     /* New block number */

      rc = lsmBlockAllocate(pFS->pDb, 0, &iNew);
      if( rc!=LSM_OK ) return rc;
      if( iApp==0 ){
        iApp = fsFirstPageOnBlock(pFS, iNew);
      }else{
        iNext = fsFirstPageOnBlock(pFS, iNew);
      }
    }
1716
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1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
      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;
}







|







1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
      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, p, fsPageToBlock(pFS, p->iLastPg), &iBlk);
      if( rc==LSM_OK ){
        lsmBlockRefree(pFS->pDb, iBlk);
      }
    }
  }
  return rc;
}
1853
1854
1855
1856
1857
1858
1859







































1860
1861
1862
1863
1864
1865
1866

/*
** Return true if page is currently writable.
*/
int lsmFsPageWritable(Page *pPg){
  return (pPg->flags & PAGE_DIRTY) ? 1 : 0;
}








































/*
** Append raw data to a segment. This function is only used in compressed
** database mode.
*/
static Pgno fsAppendData(
  FileSystem *pFS,                /* File-system handle */







>
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1911
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1955
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/*
** Return true if page is currently writable.
*/
int lsmFsPageWritable(Page *pPg){
  return (pPg->flags & PAGE_DIRTY) ? 1 : 0;
}

/*
** Copy the contents of block iFrom to block iTo. 
**
** It is safe to assume that there are no outstanding references to pages 
** on block iTo. And that block iFrom is not currently being written.
*/
int lsmFsMoveBlock(FileSystem *pFS, int iTo, int iFrom){
  Snapshot *p = pFS->pDb->pWorker;
  int rc = LSM_OK;
  
  assert( iTo!=1 );
  assert( iFrom>iTo );

  if( pFS->bUseMmap ){
    fsGrowMapping(pFS, (i64)iFrom * pFS->nBlocksize, &rc);
    if( rc==LSM_OK ){
      u8 *aMap = (u8 *)(pFS->pMap);
      i64 iFromOff = (i64)(iFrom-1) * pFS->nBlocksize;
      i64 iToOff = (i64)(iTo-1) * pFS->nBlocksize;
      memcpy(&aMap[iToOff], &aMap[iFromOff], pFS->nBlocksize);
    }
  }else{
    assert( 0 );
  }

  /* Update append-point list if necessary */
  if( rc==LSM_OK ){
    int i;
    for(i=0; i<LSM_APPLIST_SZ; i++){
      if( fsPageToBlock(pFS, p->aiAppend[i])==iFrom ){
        const int nPagePerBlock = (pFS->nBlocksize / pFS->nPagesize);
        p->aiAppend[i] -= (i64)(iFrom-iTo) * nPagePerBlock;
      }
    }
  }

  return rc;
}

/*
** Append raw data to a segment. This function is only used in compressed
** database mode.
*/
static Pgno fsAppendData(
  FileSystem *pFS,                /* File-system handle */
1880
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1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894

    /* If this is the first data written into the segment, find an append-point
    ** or allocate a new block.  */
    if( iApp==1 ){
      pSeg->iFirst = iApp = findAppendPoint(pFS, 0);
      if( iApp==0 ){
        int iBlk;
        rc = lsmBlockAllocate(pFS->pDb, &iBlk);
        pSeg->iFirst = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }
    }
    iRet = iApp;

    /* Write as much data as is possible at iApp (usually all of it). */
    iLastOnBlock = fsLastPageOnPagesBlock(pFS, iApp);







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1977
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1981
1982
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1984
1985
1986
1987
1988
1989
1990
1991

    /* If this is the first data written into the segment, find an append-point
    ** or allocate a new block.  */
    if( iApp==1 ){
      pSeg->iFirst = iApp = findAppendPoint(pFS, 0);
      if( iApp==0 ){
        int iBlk;
        rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);
        pSeg->iFirst = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }
    }
    iRet = iApp;

    /* Write as much data as is possible at iApp (usually all of it). */
    iLastOnBlock = fsLastPageOnPagesBlock(pFS, iApp);
1909
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1913
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1936
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1943
    assert( nRem<=0 || (iApp-1)==iLastOnBlock );
    if( rc==LSM_OK && (iApp-1)==iLastOnBlock ){
      u8 aPtr[4];                 /* Space to serialize a u32 */
      int iBlk;                   /* New block number */

      if( nWrite>0 ){
        /* Allocate a new block. */
        rc = lsmBlockAllocate(pFS->pDb, &iBlk);

        /* Set the "next" pointer on the old block */
        if( rc==LSM_OK ){
          assert( iApp==(fsPageToBlock(pFS, iApp)*pFS->nBlocksize)-4 );
          lsmPutU32(aPtr, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, aPtr, sizeof(aPtr));
        }

        /* Set the "prev" pointer on the new block */
        if( rc==LSM_OK ){
          Pgno iWrite;
          lsmPutU32(aPtr, fsPageToBlock(pFS, iApp));
          iWrite = fsFirstPageOnBlock(pFS, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iWrite-4, aPtr, sizeof(aPtr));
          if( nRem>0 ) iApp = iWrite;
        }
      }else{
        /* The next block is already allocated. */
        assert( nRem>0 );

        rc = fsBlockNext(pFS, fsPageToBlock(pFS, iApp), &iBlk);
        iRet = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }

      /* Write the remaining data into the new block */
      if( rc==LSM_OK && nRem>0 ){
        rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, &aData[nWrite], nRem);
        iApp += nRem;







|



















>
|







2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
    assert( nRem<=0 || (iApp-1)==iLastOnBlock );
    if( rc==LSM_OK && (iApp-1)==iLastOnBlock ){
      u8 aPtr[4];                 /* Space to serialize a u32 */
      int iBlk;                   /* New block number */

      if( nWrite>0 ){
        /* Allocate a new block. */
        rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);

        /* Set the "next" pointer on the old block */
        if( rc==LSM_OK ){
          assert( iApp==(fsPageToBlock(pFS, iApp)*pFS->nBlocksize)-4 );
          lsmPutU32(aPtr, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, aPtr, sizeof(aPtr));
        }

        /* Set the "prev" pointer on the new block */
        if( rc==LSM_OK ){
          Pgno iWrite;
          lsmPutU32(aPtr, fsPageToBlock(pFS, iApp));
          iWrite = fsFirstPageOnBlock(pFS, iBlk);
          rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iWrite-4, aPtr, sizeof(aPtr));
          if( nRem>0 ) iApp = iWrite;
        }
      }else{
        /* The next block is already allocated. */
        assert( nRem>0 );
        assert( pSeg->pRedirect==0 );
        rc = fsBlockNext(pFS, 0, fsPageToBlock(pFS, iApp), &iBlk);
        iRet = iApp = fsFirstPageOnBlock(pFS, iBlk);
      }

      /* Write the remaining data into the new block */
      if( rc==LSM_OK && nRem>0 ){
        rc = lsmEnvWrite(pFS->pEnv, pFS->fdDb, iApp, &aData[nWrite], nRem);
        iApp += nRem;
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1992
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1994
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1996

1997
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2012
2013
  if( fsIsLast(pFS, iPrev) ){
    /* Grab the first page on the next block (which has already be
    ** allocated). In this case set *piPrev to tell the caller to set
    ** the "previous block" pointer in the first 4 bytes of the page.
    */
    int iNext;
    int iBlk = fsPageToBlock(pFS, iPrev);

    rc = fsBlockNext(pFS, iBlk, &iNext);
    if( rc!=LSM_OK ) return rc;
    *piNew = fsFirstPageOnBlock(pFS, iNext);
    *piPrev = iBlk;
  }else{
    *piNew = iPrev+1;
    if( fsIsLast(pFS, *piNew) ){
      /* Allocate the next block here. */
      int iBlk;
      rc = lsmBlockAllocate(pFS->pDb, &iBlk);
      if( rc!=LSM_OK ) return rc;
      *piNext = iBlk;
    }
  }

  pSeg->nSize++;
  pSeg->iLastPg = *piNew;







>
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|







2088
2089
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2112
  if( fsIsLast(pFS, iPrev) ){
    /* Grab the first page on the next block (which has already be
    ** allocated). In this case set *piPrev to tell the caller to set
    ** the "previous block" pointer in the first 4 bytes of the page.
    */
    int iNext;
    int iBlk = fsPageToBlock(pFS, iPrev);
    assert( pSeg->pRedirect==0 );
    rc = fsBlockNext(pFS, 0, iBlk, &iNext);
    if( rc!=LSM_OK ) return rc;
    *piNew = fsFirstPageOnBlock(pFS, iNext);
    *piPrev = iBlk;
  }else{
    *piNew = iPrev+1;
    if( fsIsLast(pFS, *piNew) ){
      /* Allocate the next block here. */
      int iBlk;
      rc = lsmBlockAllocate(pFS->pDb, 0, &iBlk);
      if( rc!=LSM_OK ) return rc;
      *piNext = iBlk;
    }
  }

  pSeg->nSize++;
  pSeg->iLastPg = *piNew;
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
    iBlk = fsPageToBlock(pFS, pArray->iFirst);
    iLastBlk = fsPageToBlock(pFS, pArray->iLastPg);

    lsmStringInit(&str, pDb->pEnv);
    if( bBlock ){
      lsmStringAppendf(&str, "%d", iBlk);
      while( iBlk!=iLastBlk ){
        fsBlockNext(pFS, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", iBlk);
      }
    }else{
      lsmStringAppendf(&str, "%d", pArray->iFirst);
      while( iBlk!=iLastBlk ){
        lsmStringAppendf(&str, " %d", fsLastPageOnBlock(pFS, iBlk));
        fsBlockNext(pFS, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", fsFirstPageOnBlock(pFS, iBlk));
      }
      lsmStringAppendf(&str, " %d", pArray->iLastPg);
    }

    *pzOut = str.z;
  }







|






|







2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
    iBlk = fsPageToBlock(pFS, pArray->iFirst);
    iLastBlk = fsPageToBlock(pFS, pArray->iLastPg);

    lsmStringInit(&str, pDb->pEnv);
    if( bBlock ){
      lsmStringAppendf(&str, "%d", iBlk);
      while( iBlk!=iLastBlk ){
        fsBlockNext(pFS, pArray, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", iBlk);
      }
    }else{
      lsmStringAppendf(&str, "%d", pArray->iFirst);
      while( iBlk!=iLastBlk ){
        lsmStringAppendf(&str, " %d", fsLastPageOnBlock(pFS, iBlk));
        fsBlockNext(pFS, pArray, iBlk, &iBlk);
        lsmStringAppendf(&str, " %d", fsFirstPageOnBlock(pFS, iBlk));
      }
      lsmStringAppendf(&str, " %d", pArray->iLastPg);
    }

    *pzOut = str.z;
  }
2473
2474
2475
2476
2477
2478
2479

2480
2481

2482
2483
2484
2485
2486
2487



2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
  Segment *pSeg,
  int bExtra,                     /* If true, count the "next" block if any */
  int nUsed,
  u8 *aUsed
){
  if( pSeg ){
    if( pSeg && pSeg->nSize>0 ){

      int rc;
      Pgno iLast = pSeg->iLastPg;

      int iBlk;
      int iLastBlk;
      int bLastIsLastOnBlock;

      iBlk = fsPageToBlock(pFS, pSeg->iFirst);
      iLastBlk = fsPageToBlock(pFS, pSeg->iLastPg);



      bLastIsLastOnBlock = (fsLastPageOnBlock(pFS, iLastBlk)==iLast);
      assert( iBlk>0 );

      /* If the first page of this run is also the first page of its first
      ** block, set the flag to indicate that the first page of iBlk is 
      ** in use.  */
      if( fsFirstPageOnBlock(pFS, iBlk)==pSeg->iFirst ){
        assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_FIRST_PG)==0 );
        aUsed[iBlk-1] |= INTEGRITY_CHECK_FIRST_PG;
      }

      do {
        /* iBlk is a part of this sorted run. */
        aUsed[iBlk-1] |= INTEGRITY_CHECK_USED;







>

|
>
|
|
|

|
|
>
>
>






|







2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
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2590
2591
2592
2593
2594
2595
2596
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2598
2599
2600
2601
2602
2603
2604
2605
  Segment *pSeg,
  int bExtra,                     /* If true, count the "next" block if any */
  int nUsed,
  u8 *aUsed
){
  if( pSeg ){
    if( pSeg && pSeg->nSize>0 ){
      Redirect *pRedir = pSeg->pRedirect;
      int rc;
      Pgno iLast;                 /* Last page of segment (post-redirection) */
      Pgno iFirst;                /* First page of segment (post-redirection) */
      int iBlk;                   /* Current block (during iteration) */
      int iLastBlk;               /* Last real block of segment */
      int bLastIsLastOnBlock;     /* True iLast is the last on its block */

      iBlk = fsRedirectBlock(pRedir, fsPageToBlock(pFS, pSeg->iFirst));
      iLastBlk = fsRedirectBlock(pRedir, fsPageToBlock(pFS, pSeg->iLastPg));
      iLast = fsRedirectPage(pFS, pRedir, pSeg->iLastPg);
      iFirst = fsRedirectPage(pFS, pRedir, pSeg->iFirst);

      bLastIsLastOnBlock = (fsLastPageOnBlock(pFS, iLastBlk)==iLast);
      assert( iBlk>0 );

      /* If the first page of this run is also the first page of its first
      ** block, set the flag to indicate that the first page of iBlk is 
      ** in use.  */
      if( fsFirstPageOnBlock(pFS, iBlk)==iFirst ){
        assert( (aUsed[iBlk-1] & INTEGRITY_CHECK_FIRST_PG)==0 );
        aUsed[iBlk-1] |= INTEGRITY_CHECK_FIRST_PG;
      }

      do {
        /* iBlk is a part of this sorted run. */
        aUsed[iBlk-1] |= INTEGRITY_CHECK_USED;
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538

        /* Special case. The sorted run being scanned is the output run of
        ** a level currently undergoing an incremental merge. The sorted
        ** run ends on the last page of iBlk, but the next block has already
        ** been allocated. So mark it as in use as well.  */
        if( iBlk==iLastBlk && bLastIsLastOnBlock && bExtra ){
          int iExtra = 0;
          rc = fsBlockNext(pFS, iBlk, &iExtra);
          assert( rc==LSM_OK );

          assert( aUsed[iExtra-1]==0 );
          aUsed[iExtra-1] |= INTEGRITY_CHECK_USED;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_FIRST_PG;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_LAST_PG;
        }

        /* Move on to the next block in the sorted run. Or set iBlk to zero
        ** in order to break out of the loop if this was the last block in
        ** the run.  */
        if( iBlk==iLastBlk ){
          iBlk = 0;
        }else{
          rc = fsBlockNext(pFS, iBlk, &iBlk);
          assert( rc==LSM_OK );
        }
      }while( iBlk );
    }
  }
}








|














|







2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642

        /* Special case. The sorted run being scanned is the output run of
        ** a level currently undergoing an incremental merge. The sorted
        ** run ends on the last page of iBlk, but the next block has already
        ** been allocated. So mark it as in use as well.  */
        if( iBlk==iLastBlk && bLastIsLastOnBlock && bExtra ){
          int iExtra = 0;
          rc = fsBlockNext(pFS, pSeg, iBlk, &iExtra);
          assert( rc==LSM_OK );

          assert( aUsed[iExtra-1]==0 );
          aUsed[iExtra-1] |= INTEGRITY_CHECK_USED;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_FIRST_PG;
          aUsed[iExtra-1] |= INTEGRITY_CHECK_LAST_PG;
        }

        /* Move on to the next block in the sorted run. Or set iBlk to zero
        ** in order to break out of the loop if this was the last block in
        ** the run.  */
        if( iBlk==iLastBlk ){
          iBlk = 0;
        }else{
          rc = fsBlockNext(pFS, pSeg, iBlk, &iBlk);
          assert( rc==LSM_OK );
        }
      }while( iBlk );
    }
  }
}

Changes to src/lsm_shared.c.
623
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629

630
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634
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636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
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655
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657
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673
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675
676
677
678
679
}


typedef struct FindFreeblockCtx FindFreeblockCtx;
struct FindFreeblockCtx {
  i64 iInUse;
  int iRet;

};

static int findFreeblockCb(void *pCtx, int iBlk, i64 iSnapshot){
  FindFreeblockCtx *p = (FindFreeblockCtx *)pCtx;
  if( iSnapshot<p->iInUse ){
    p->iRet = iBlk;
    return 1;
  }
  return 0;
}

static int findFreeblock(lsm_db *pDb, i64 iInUse, int *piRet){
  int rc;                         /* Return code */
  FindFreeblockCtx ctx;           /* Context object */

#ifdef LSM_LOG_BLOCKS
  char *zList = 0;
  lsmInfoFreelist(pDb, &zList);
  lsmLogMessage(pDb, 0, 
      "findFreeblock(): iInUse=%lld freelist=%s", iInUse, zList);
  lsmFree(pDb->pEnv, zList);
#endif

  ctx.iInUse = iInUse;
  ctx.iRet = 0;

  rc = lsmWalkFreelist(pDb, 0, findFreeblockCb, (void *)&ctx);
  *piRet = ctx.iRet;

#ifdef LSM_LOG_BLOCKS
  lsmLogMessage(pDb, 0, "findFreeblock(): returning block %d", *piRet);
#endif
  return rc;
}

/*
** Allocate a new database file block to write data to, either by extending
** the database file or by recycling a free-list entry. The worker snapshot 
** must be held in order to call this function.
**
** If successful, *piBlk is set to the block number allocated and LSM_OK is
** returned. Otherwise, *piBlk is zeroed and an lsm error code returned.
*/
int lsmBlockAllocate(lsm_db *pDb, int *piBlk){
  Snapshot *p = pDb->pWorker;
  int iRet = 0;                   /* Block number of allocated block */
  int rc = LSM_OK;
  i64 iInUse = 0;                 /* Snapshot id still in use */
  i64 iSynced = 0;                /* Snapshot id synced to disk */

  assert( p );







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}


typedef struct FindFreeblockCtx FindFreeblockCtx;
struct FindFreeblockCtx {
  i64 iInUse;
  int iRet;
  int bNotOne;
};

static int findFreeblockCb(void *pCtx, int iBlk, i64 iSnapshot){
  FindFreeblockCtx *p = (FindFreeblockCtx *)pCtx;
  if( iSnapshot<p->iInUse && (iBlk!=1 || p->bNotOne==0) ){
    p->iRet = iBlk;
    return 1;
  }
  return 0;
}

static int findFreeblock(lsm_db *pDb, i64 iInUse, int bNotOne, int *piRet){
  int rc;                         /* Return code */
  FindFreeblockCtx ctx;           /* Context object */









  ctx.iInUse = iInUse;
  ctx.iRet = 0;
  ctx.bNotOne = bNotOne;
  rc = lsmWalkFreelist(pDb, 0, findFreeblockCb, (void *)&ctx);
  *piRet = ctx.iRet;




  return rc;
}

/*
** Allocate a new database file block to write data to, either by extending
** the database file or by recycling a free-list entry. The worker snapshot 
** must be held in order to call this function.
**
** If successful, *piBlk is set to the block number allocated and LSM_OK is
** returned. Otherwise, *piBlk is zeroed and an lsm error code returned.
*/
int lsmBlockAllocate(lsm_db *pDb, int iBefore, int *piBlk){
  Snapshot *p = pDb->pWorker;
  int iRet = 0;                   /* Block number of allocated block */
  int rc = LSM_OK;
  i64 iInUse = 0;                 /* Snapshot id still in use */
  i64 iSynced = 0;                /* Snapshot id synced to disk */

  assert( p );
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        "snapshot-in-use: %lld (iSynced=%lld) (client-id=%lld)", 
        iInUse, iSynced, (pDb->pClient ? pDb->pClient->iId : 0)
    );
  }
#endif

  /* Query the free block list for a suitable block */
  if( rc==LSM_OK ) rc = findFreeblock(pDb, iInUse, &iRet);





  /* If a block was found in the free block list, use it and remove it from 
  ** the list. Otherwise, if no suitable block was found, allocate one from
  ** the end of the file.  */
  if( rc==LSM_OK ){
    if( iRet>0 ){
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, 
          "reusing block %d (snapshot-in-use=%lld)", iRet, iInUse);
#endif
      rc = freelistAppend(pDb, iRet, -1);
      if( rc==LSM_OK ){
        rc = dbTruncate(pDb, iInUse);
      }
    }else{
      iRet = ++(p->nBlock);
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, "extending file to %d blocks", iRet);
#endif
    }
  }

  assert( iRet>0 || rc!=LSM_OK );
  *piBlk = iRet;
  return rc;
}

/*
** Free a database block. The worker snapshot must be held in order to call 
** this function.







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        "snapshot-in-use: %lld (iSynced=%lld) (client-id=%lld)", 
        iInUse, iSynced, (pDb->pClient ? pDb->pClient->iId : 0)
    );
  }
#endif

  /* Query the free block list for a suitable block */
  if( rc==LSM_OK ) rc = findFreeblock(pDb, iInUse, (iBefore>0), &iRet);

  if( iBefore>0 && (iRet<=0 || iRet>=iBefore) ){
    iRet = 0;

  }else if( rc==LSM_OK ){
    /* If a block was found in the free block list, use it and remove it from 
    ** the list. Otherwise, if no suitable block was found, allocate one from
    ** the end of the file.  */

    if( iRet>0 ){
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, 
          "reusing block %d (snapshot-in-use=%lld)", iRet, iInUse);
#endif
      rc = freelistAppend(pDb, iRet, -1);
      if( rc==LSM_OK ){
        rc = dbTruncate(pDb, iInUse);
      }
    }else{
      iRet = ++(p->nBlock);
#ifdef LSM_LOG_FREELIST
      lsmLogMessage(pDb, 0, "extending file to %d blocks", iRet);
#endif
    }
  }

  assert( iBefore>0 || iRet>0 || rc!=LSM_OK );
  *piBlk = iRet;
  return rc;
}

/*
** Free a database block. The worker snapshot must be held in order to call 
** this function.
Changes to src/lsm_sorted.c.
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   && (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 */







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

typedef struct MoveBlockCtx MoveBlockCtx;
struct MoveBlockCtx {
  int iSeen;                      /* Previous free block on list */
  int iFrom;                      /* Total number of blocks in file */
};

static int moveBlockCb(void *pCtx, int iBlk, i64 iSnapshot){
  MoveBlockCtx *p = (MoveBlockCtx *)pCtx;
  assert( p->iFrom==0 );
  if( iBlk==(p->iSeen-1) ){
    p->iSeen = iBlk;
    return 0;
  }
  p->iFrom = p->iSeen-1;
  return 1;
}

/*
** This function is called to further compact a database for which all 
** of the content has already been merged into a single segment. If 
** possible, it moves the contents of a single block from the end of the
** file to a free-block that lies closer to the start of the file (allowing
** the file to be eventually truncated).
*/
static int sortedMoveBlock(lsm_db *pDb, int *pnWrite){
  Snapshot *p = pDb->pWorker;
  Level *pLvl = lsmDbSnapshotLevel(p);
  int iFrom;                      /* Block to move */
  int iTo;                        /* Destination to move block to */
  int rc;                         /* Return code */

  MoveBlockCtx sCtx;

  assert( pLvl->pNext==0 && pLvl->nRight==0 );
  assert( p->redirect.n<=LSM_MAX_BLOCK_REDIRECTS );

  *pnWrite = 0;

  /* Check that the redirect array is not already full. If it is, return
  ** without moving any database content.  */
  if( p->redirect.n>=LSM_MAX_BLOCK_REDIRECTS ) return LSM_OK;

  /* Find the last block of content in the database file. Do this by 
  ** traversing the free-list in reverse (descending block number) order.
  ** The first block not on the free list is the one that will be moved.
  ** Since the db consists of a single segment, there is no ambiguity as
  ** to which segment the block belongs to.  */
  sCtx.iSeen = p->nBlock+1;
  sCtx.iFrom = 0;
  rc = lsmWalkFreelist(pDb, 1, moveBlockCb, &sCtx);
  if( rc!=LSM_OK || sCtx.iFrom==0 ) return rc;
  iFrom = sCtx.iFrom;

  /* Find the first free block in the database, ignoring block 1. Block
  ** 1 is tricky as it is smaller than the other blocks.  */
  rc = lsmBlockAllocate(pDb, iFrom, &iTo);
  if( rc!=LSM_OK || iTo==0 ) return rc;
  assert( iTo!=1 && iTo<iFrom );

  rc = lsmFsMoveBlock(pDb->pFS, iTo, iFrom);
  if( rc==LSM_OK ){
    if( p->redirect.a==0 ){
      int nByte = sizeof(struct RedirectEntry) * LSM_MAX_BLOCK_REDIRECTS;
      p->redirect.a = lsmMallocZeroRc(pDb->pEnv, nByte, &rc);
    }
    if( rc==LSM_OK ){
      memmove(&p->redirect.a[1], &p->redirect.a[0], 
          sizeof(struct RedirectEntry) * p->redirect.n
      );
      p->redirect.a[0].iFrom = iFrom;
      p->redirect.a[0].iTo = iTo;
      p->redirect.n++;

      rc = lsmBlockFree(pDb, iFrom);

      *pnWrite = lsmFsBlockSize(pDb->pFS) / lsmFsPageSize(pDb->pFS);
      pLvl->lhs.pRedirect = &p->redirect;
    }
  }

  return rc;
}

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 */
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    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 */







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    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 = sortedMoveBlock(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 */