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Overview
Comment:Fix harmless compiler warnings in the cell-overwrite logic.
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SHA3-256: 3e11dc3183bc3e8ec49af244a8e8b3e07d12f7a2e59028b2bf64ce0ab589a91f
User & Date: drh 2018-05-07 11:29:59
Context
2018-05-07
11:48
On an UPDATE, try to overwrite an existing btree cell with the modified content, if the old and new cell are the same size. Use memcmp() first to avoid dirtying pages that are unchanged. check-in: 5887d8be user: drh tags: trunk
11:29
Fix harmless compiler warnings in the cell-overwrite logic. Closed-Leaf check-in: 3e11dc31 user: drh tags: cell-overwrite-prototype
2018-05-04
19:18
Merge enhancements from trunk. check-in: 9650f71b user: drh tags: cell-overwrite-prototype
Changes
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Changes to src/btree.c.

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  rc = btreeOverwriteContent(pPage, pCur->info.pPayload, pX,
                             0, pCur->info.nLocal);
  if( rc ) return rc;
  if( pCur->info.nLocal==nTotal ) return SQLITE_OK;

  /* Now overwrite the overflow pages */
  iOffset = pCur->info.nLocal;


  ovflPgno = get4byte(pCur->info.pPayload + iOffset);
  pBt = pPage->pBt;
  ovflPageSize = pBt->usableSize - 4;
  do{
    rc = btreeGetPage(pBt, ovflPgno, &pPage, 0);
    if( rc ) return rc;
    if( sqlite3PagerPageRefcount(pPage->pDbPage)!=1 ){
      rc = SQLITE_CORRUPT_BKPT;
    }else{
      if( iOffset+ovflPageSize<nTotal ){
        ovflPgno = get4byte(pPage->aData);
      }else{
        ovflPageSize = nTotal - iOffset;
      }
      rc = btreeOverwriteContent(pPage, pPage->aData+4, pX,
                                 iOffset, ovflPageSize);
    }
................................................................................

    /* If the cursor is currently on the last row and we are appending a
    ** new row onto the end, set the "loc" to avoid an unnecessary
    ** btreeMoveto() call */
    if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey==pCur->info.nKey ){
      /* The current is currently pointing to the entry that is to be
      ** overwritten */

      if( pCur->info.nSize!=0 && pCur->info.nPayload==pX->nData+pX->nZero ){


        return btreeOverwriteCell(pCur, pX);
      }
      loc = 0;
    }else if( loc==0 ){
      rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, flags!=0, &loc);
      if( rc ) return rc;
    }







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  rc = btreeOverwriteContent(pPage, pCur->info.pPayload, pX,
                             0, pCur->info.nLocal);
  if( rc ) return rc;
  if( pCur->info.nLocal==nTotal ) return SQLITE_OK;

  /* Now overwrite the overflow pages */
  iOffset = pCur->info.nLocal;
  assert( nTotal>=0 );
  assert( iOffset>=0 );
  ovflPgno = get4byte(pCur->info.pPayload + iOffset);
  pBt = pPage->pBt;
  ovflPageSize = pBt->usableSize - 4;
  do{
    rc = btreeGetPage(pBt, ovflPgno, &pPage, 0);
    if( rc ) return rc;
    if( sqlite3PagerPageRefcount(pPage->pDbPage)!=1 ){
      rc = SQLITE_CORRUPT_BKPT;
    }else{
      if( iOffset+ovflPageSize<(u32)nTotal ){
        ovflPgno = get4byte(pPage->aData);
      }else{
        ovflPageSize = nTotal - iOffset;
      }
      rc = btreeOverwriteContent(pPage, pPage->aData+4, pX,
                                 iOffset, ovflPageSize);
    }
................................................................................

    /* If the cursor is currently on the last row and we are appending a
    ** new row onto the end, set the "loc" to avoid an unnecessary
    ** btreeMoveto() call */
    if( (pCur->curFlags&BTCF_ValidNKey)!=0 && pX->nKey==pCur->info.nKey ){
      /* The current is currently pointing to the entry that is to be
      ** overwritten */
      assert( pX->nData>=0 && pX->nZero>=0 );
      if( pCur->info.nSize!=0
       && pCur->info.nPayload==(u32)pX->nData+pX->nZero
      ){
        return btreeOverwriteCell(pCur, pX);
      }
      loc = 0;
    }else if( loc==0 ){
      rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, flags!=0, &loc);
      if( rc ) return rc;
    }