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Overview
Comment:Optimizations associated with error handling in btree cursors.
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SHA3-256: 49ba54e26731ed371745d4bdd9dd1dfeb73357b6d206c85a4252ec866be971d0
User & Date: drh 2017-08-02 15:50:09
Context
2017-08-02
18:27
Minor optimization on clearCell() check-in: f3c39c29 user: drh tags: trunk
15:50
Optimizations associated with error handling in btree cursors. check-in: 49ba54e2 user: drh tags: trunk
12:38
Remove unused token codes. check-in: c45078c0 user: drh tags: trunk
Changes
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Changes to src/btree.c.

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    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
      if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
        int rc = saveCursorPosition(p);
        if( SQLITE_OK!=rc ){
          return rc;
        }
      }else{
        testcase( p->iPage>0 );
        btreeReleaseAllCursorPages(p);
      }
    }
    p = p->pNext;
  }while( p );
  return SQLITE_OK;
}
................................................................................
  BtCursor *p;
  int rc = SQLITE_OK;

  assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
  if( pBtree ){
    sqlite3BtreeEnter(pBtree);
    for(p=pBtree->pBt->pCursor; p; p=p->pNext){
      int i;
      if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
        if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
          rc = saveCursorPosition(p);
          if( rc!=SQLITE_OK ){
            (void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
            break;
          }
        }
      }else{
        sqlite3BtreeClearCursor(p);
        p->eState = CURSOR_FAULT;
        p->skipNext = errCode;
      }
      for(i=0; i<=p->iPage; i++){
        releasePage(p->apPage[i]);
        p->apPage[i] = 0;
      }
    }
    sqlite3BtreeLeave(pBtree);
  }
  return rc;
}

/*
................................................................................
          pPrev->pNext = pCur->pNext;
          break;
        }
        pPrev = pPrev->pNext;
      }while( ALWAYS(pPrev) );
    }
    for(i=0; i<=pCur->iPage; i++){
      releasePage(pCur->apPage[i]);
    }
    unlockBtreeIfUnused(pBt);
    sqlite3_free(pCur->aOverflow);
    /* sqlite3_free(pCur); */
    sqlite3BtreeLeave(pBtree);
  }
  return SQLITE_OK;
................................................................................
  MemPage *pRoot;
  int rc = SQLITE_OK;

  assert( cursorOwnsBtShared(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  if( pCur->eState>=CURSOR_REQUIRESEEK ){
    if( pCur->eState==CURSOR_FAULT ){
      assert( pCur->skipNext!=SQLITE_OK );
      return pCur->skipNext;
    }
    sqlite3BtreeClearCursor(pCur);
  }

  if( pCur->iPage>=0 ){
    if( pCur->iPage ){
      do{
        assert( pCur->apPage[pCur->iPage]!=0 );
        releasePageNotNull(pCur->apPage[pCur->iPage--]);
      }while( pCur->iPage);
................................................................................
      goto skip_init;
    }
  }else if( pCur->pgnoRoot==0 ){
    pCur->eState = CURSOR_INVALID;
    return SQLITE_OK;
  }else{
    assert( pCur->iPage==(-1) );







    rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
                        0, pCur->curPagerFlags);
    if( rc!=SQLITE_OK ){
      pCur->eState = CURSOR_INVALID;
       return rc;
    }
    pCur->iPage = 0;
................................................................................
    /* Must make sure nOverflow is reset to zero even if the balance()
    ** fails. Internal data structure corruption will result otherwise. 
    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
    ** from trying to save the current position of the cursor.  */
    pCur->apPage[pCur->iPage]->nOverflow = 0;
    pCur->eState = CURSOR_INVALID;
    if( (flags & BTREE_SAVEPOSITION) && rc==SQLITE_OK ){
      rc = moveToRoot(pCur);
      if( pCur->pKeyInfo ){
        assert( pCur->pKey==0 );
        pCur->pKey = sqlite3Malloc( pX->nKey );
        if( pCur->pKey==0 ){
          rc = SQLITE_NOMEM;
        }else{
          memcpy(pCur->pKey, pX->pKey, pX->nKey);
        }
      }
      pCur->eState = CURSOR_REQUIRESEEK;
      pCur->nKey = pX->nKey;
    }
  }
  assert( pCur->apPage[pCur->iPage]->nOverflow==0 );

end_insert:
  return rc;
}

/*
** Delete the entry that the cursor is pointing to. 
................................................................................
        pCur->ix = pPage->nCell-1;
      }else{
        pCur->skipNext = 1;
      }
    }else{
      rc = moveToRoot(pCur);
      if( bPreserve ){

        pCur->eState = CURSOR_REQUIRESEEK;
      }
    }
  }
  return rc;
}








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    if( p!=pExcept && (0==iRoot || p->pgnoRoot==iRoot) ){
      if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
        int rc = saveCursorPosition(p);
        if( SQLITE_OK!=rc ){
          return rc;
        }
      }else{
        testcase( p->iPage>=0 );
        btreeReleaseAllCursorPages(p);
      }
    }
    p = p->pNext;
  }while( p );
  return SQLITE_OK;
}
................................................................................
  BtCursor *p;
  int rc = SQLITE_OK;

  assert( (writeOnly==0 || writeOnly==1) && BTCF_WriteFlag==1 );
  if( pBtree ){
    sqlite3BtreeEnter(pBtree);
    for(p=pBtree->pBt->pCursor; p; p=p->pNext){

      if( writeOnly && (p->curFlags & BTCF_WriteFlag)==0 ){
        if( p->eState==CURSOR_VALID || p->eState==CURSOR_SKIPNEXT ){
          rc = saveCursorPosition(p);
          if( rc!=SQLITE_OK ){
            (void)sqlite3BtreeTripAllCursors(pBtree, rc, 0);
            break;
          }
        }
      }else{
        sqlite3BtreeClearCursor(p);
        p->eState = CURSOR_FAULT;
        p->skipNext = errCode;
      }
      btreeReleaseAllCursorPages(p);



    }
    sqlite3BtreeLeave(pBtree);
  }
  return rc;
}

/*
................................................................................
          pPrev->pNext = pCur->pNext;
          break;
        }
        pPrev = pPrev->pNext;
      }while( ALWAYS(pPrev) );
    }
    for(i=0; i<=pCur->iPage; i++){
      releasePageNotNull(pCur->apPage[i]);
    }
    unlockBtreeIfUnused(pBt);
    sqlite3_free(pCur->aOverflow);
    /* sqlite3_free(pCur); */
    sqlite3BtreeLeave(pBtree);
  }
  return SQLITE_OK;
................................................................................
  MemPage *pRoot;
  int rc = SQLITE_OK;

  assert( cursorOwnsBtShared(pCur) );
  assert( CURSOR_INVALID < CURSOR_REQUIRESEEK );
  assert( CURSOR_VALID   < CURSOR_REQUIRESEEK );
  assert( CURSOR_FAULT   > CURSOR_REQUIRESEEK );
  assert( pCur->eState < CURSOR_REQUIRESEEK || pCur->iPage<0 );







  if( pCur->iPage>=0 ){
    if( pCur->iPage ){
      do{
        assert( pCur->apPage[pCur->iPage]!=0 );
        releasePageNotNull(pCur->apPage[pCur->iPage--]);
      }while( pCur->iPage);
................................................................................
      goto skip_init;
    }
  }else if( pCur->pgnoRoot==0 ){
    pCur->eState = CURSOR_INVALID;
    return SQLITE_OK;
  }else{
    assert( pCur->iPage==(-1) );
    if( pCur->eState>=CURSOR_REQUIRESEEK ){
      if( pCur->eState==CURSOR_FAULT ){
        assert( pCur->skipNext!=SQLITE_OK );
        return pCur->skipNext;
      }
      sqlite3BtreeClearCursor(pCur);
    }
    rc = getAndInitPage(pCur->pBtree->pBt, pCur->pgnoRoot, &pCur->apPage[0],
                        0, pCur->curPagerFlags);
    if( rc!=SQLITE_OK ){
      pCur->eState = CURSOR_INVALID;
       return rc;
    }
    pCur->iPage = 0;
................................................................................
    /* Must make sure nOverflow is reset to zero even if the balance()
    ** fails. Internal data structure corruption will result otherwise. 
    ** Also, set the cursor state to invalid. This stops saveCursorPosition()
    ** from trying to save the current position of the cursor.  */
    pCur->apPage[pCur->iPage]->nOverflow = 0;
    pCur->eState = CURSOR_INVALID;
    if( (flags & BTREE_SAVEPOSITION) && rc==SQLITE_OK ){
      btreeReleaseAllCursorPages(pCur);
      if( pCur->pKeyInfo ){
        assert( pCur->pKey==0 );
        pCur->pKey = sqlite3Malloc( pX->nKey );
        if( pCur->pKey==0 ){
          rc = SQLITE_NOMEM;
        }else{
          memcpy(pCur->pKey, pX->pKey, pX->nKey);
        }
      }
      pCur->eState = CURSOR_REQUIRESEEK;
      pCur->nKey = pX->nKey;
    }
  }
  assert( pCur->iPage<0 || pCur->apPage[pCur->iPage]->nOverflow==0 );

end_insert:
  return rc;
}

/*
** Delete the entry that the cursor is pointing to. 
................................................................................
        pCur->ix = pPage->nCell-1;
      }else{
        pCur->skipNext = 1;
      }
    }else{
      rc = moveToRoot(pCur);
      if( bPreserve ){
        btreeReleaseAllCursorPages(pCur);
        pCur->eState = CURSOR_REQUIRESEEK;
      }
    }
  }
  return rc;
}