sqliteVdbeAddOp(v, OP_NotExists, iCur, addr);
sqliteVdbeAddOp(v, OP_NotExists, iCur, loopStart);
void sqliteUpdate(  Parse *pParse,         /* The parser context */  SrcList *pTabList,     /* The table in which we should change things */  ExprList *pChanges,    /* Things to be changed */  Expr *pWhere,          /* The WHERE clause.  May be null */  int onError            /* How to handle constraint errors */){  int i, j;              /* Loop counters */  Table *pTab;           /* The table to be updated */  int addr;              /* VDBE instruction address of the start of the loop */  WhereInfo *pWInfo;     /* Information about the WHERE clause */  Vdbe *v;               /* The virtual database engine */  Index *pIdx;           /* For looping over indices */  int nIdx;              /* Number of indices that need updating */  int nIdxTotal;         /* Total number of indices */  int iCur;              /* VDBE Cursor number of pTab */  sqlite *db;            /* The database structure */  Index **apIdx = 0;     /* An array of indices that need updating too */  char *aIdxUsed = 0;    /* aIdxUsed[i]==1 if the i-th index is used */  int *aXRef = 0;        /* aXRef[i] is the index in pChanges->a[] of the                         ** an expression for the i-th column of the table.                         ** aXRef[i]==-1 if the i-th column is not changed. */  int chngRecno;         /* True if the record number is being changed */  Expr *pRecnoExpr;      /* Expression defining the new record number */  int openAll;           /* True if all indices need to be opened */  int isView;            /* Trying to update a view */  AuthContext sContext;  /* The authorization context */  int before_triggers;         /* True if there are any BEFORE triggers */  int after_triggers;          /* True if there are any AFTER triggers */  int row_triggers_exist = 0;  /* True if any row triggers exist */  int newIdx      = -1;  /* index of trigger "new" temp table       */  int oldIdx      = -1;  /* index of trigger "old" temp table       */  sContext.pParse = 0;  if( pParse->nErr || sqlite_malloc_failed ) goto update_cleanup;  db = pParse->db;  assert( pTabList->nSrc==1 );  /* Locate the table which we want to update.   */  pTab = sqliteSrcListLookup(pParse, pTabList);  if( pTab==0 ) goto update_cleanup;  before_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,             TK_UPDATE, TK_BEFORE, TK_ROW, pChanges);  after_triggers = sqliteTriggersExist(pParse, pTab->pTrigger,             TK_UPDATE, TK_AFTER, TK_ROW, pChanges);  row_triggers_exist = before_triggers || after_triggers;  isView = pTab->pSelect!=0;  if( sqliteIsReadOnly(pParse, pTab, before_triggers) ){    goto update_cleanup;  }  if( isView ){    if( sqliteViewGetColumnNames(pParse, pTab) ){      goto update_cleanup;    }  }  aXRef = sqliteMalloc( sizeof(int) * pTab->nCol );  if( aXRef==0 ) goto update_cleanup;  for(i=0; i<pTab->nCol; i++) aXRef[i] = -1;  /* If there are FOR EACH ROW triggers, allocate cursors for the  ** special OLD and NEW tables  */  if( row_triggers_exist ){    newIdx = pParse->nTab++;    oldIdx = pParse->nTab++;  }  /* Allocate a cursors for the main database table and for all indices.  ** The index cursors might not be used, but if they are used they  ** need to occur right after the database cursor.  So go ahead and  ** allocate enough space, just in case.  */  pTabList->a[0].iCursor = iCur = pParse->nTab++;  for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){    pParse->nTab++;  }  /* Resolve the column names in all the expressions of the  ** of the UPDATE statement.  Also find the column index  ** for each column to be updated in the pChanges array.  For each  ** column to be updated, make sure we have authorization to change  ** that column.  */  chngRecno = 0;  for(i=0; i<pChanges->nExpr; i++){    if( sqliteExprResolveIds(pParse, pTabList, 0, pChanges->a[i].pExpr) ){      goto update_cleanup;    }    if( sqliteExprCheck(pParse, pChanges->a[i].pExpr, 0, 0) ){      goto update_cleanup;    }    for(j=0; j<pTab->nCol; j++){      if( sqliteStrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){        if( j==pTab->iPKey ){          chngRecno = 1;          pRecnoExpr = pChanges->a[i].pExpr;        }        aXRef[j] = i;        break;      }    }    if( j>=pTab->nCol ){      if( sqliteIsRowid(pChanges->a[i].zName) ){        chngRecno = 1;        pRecnoExpr = pChanges->a[i].pExpr;      }else{        sqliteErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);        goto update_cleanup;      }    }#ifndef SQLITE_OMIT_AUTHORIZATION    {      int rc;      rc = sqliteAuthCheck(pParse, SQLITE_UPDATE, pTab->zName,                           pTab->aCol[j].zName, db->aDb[pTab->iDb].zName);      if( rc==SQLITE_DENY ){        goto update_cleanup;      }else if( rc==SQLITE_IGNORE ){        aXRef[j] = -1;      }    }#endif  }  /* Allocate memory for the array apIdx[] and fill it with pointers to every  ** index that needs to be updated.  Indices only need updating if their  ** key includes one of the columns named in pChanges or if the record  ** number of the original table entry is changing.  */  for(nIdx=nIdxTotal=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdxTotal++){    if( chngRecno ){      i = 0;    }else {      for(i=0; i<pIdx->nColumn; i++){        if( aXRef[pIdx->aiColumn[i]]>=0 ) break;      }    }    if( i<pIdx->nColumn ) nIdx++;  }  if( nIdxTotal>0 ){    apIdx = sqliteMalloc( sizeof(Index*) * nIdx + nIdxTotal );    if( apIdx==0 ) goto update_cleanup;    aIdxUsed = (char*)&apIdx[nIdx];  }  for(nIdx=j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){    if( chngRecno ){      i = 0;    }else{      for(i=0; i<pIdx->nColumn; i++){        if( aXRef[pIdx->aiColumn[i]]>=0 ) break;      }    }    if( i<pIdx->nColumn ){      apIdx[nIdx++] = pIdx;      aIdxUsed[j] = 1;    }else{      aIdxUsed[j] = 0;    }  }  /* Resolve the column names in all the expressions in the  ** WHERE clause.  */  if( pWhere ){    if( sqliteExprResolveIds(pParse, pTabList, 0, pWhere) ){      goto update_cleanup;    }    if( sqliteExprCheck(pParse, pWhere, 0, 0) ){      goto update_cleanup;    }  }  /* Start the view context  */  if( isView ){    sqliteAuthContextPush(pParse, &sContext, pTab->zName);  }  /* Begin generating code.  */  v = sqliteGetVdbe(pParse);  if( v==0 ) goto update_cleanup;  sqliteBeginWriteOperation(pParse, 1, pTab->iDb);  /* If we are trying to update a view, construct that view into  ** a temporary table.  */  if( isView ){    Select *pView;    pView = sqliteSelectDup(pTab->pSelect);    sqliteSelect(pParse, pView, SRT_TempTable, iCur, 0, 0, 0);    sqliteSelectDelete(pView);  }  /* Begin the database scan  */  pWInfo = sqliteWhereBegin(pParse, pTabList, pWhere, 1, 0);  if( pWInfo==0 ) goto update_cleanup;  /* Remember the index of every item to be updated.  */  sqliteVdbeAddOp(v, OP_ListWrite, 0, 0);  /* End the database scan loop.  */  sqliteWhereEnd(pWInfo);  /* Initialize the count of updated rows  */  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){    sqliteVdbeAddOp(v, OP_Integer, 0, 0);  }  if( row_triggers_exist ){    /* Create pseudo-tables for NEW and OLD    */    sqliteVdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);    sqliteVdbeAddOp(v, OP_OpenPseudo, newIdx, 0);    /* The top of the update loop for when there are triggers.    */    sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);    addr = sqliteVdbeAddOp(v, OP_ListRead, 0, 0);    sqliteVdbeAddOp(v, OP_Dup, 0, 0);    /* Open a cursor and make it point to the record that is    ** being updated.    */    sqliteVdbeAddOp(v, OP_Dup, 0, 0);    if( !isView ){      sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);      sqliteVdbeAddOp(v, OP_OpenRead, iCur, pTab->tnum);    }    sqliteVdbeAddOp(v, OP_MoveTo, iCur, 0);    /* Generate the OLD table    */    sqliteVdbeAddOp(v, OP_Recno, iCur, 0);    sqliteVdbeAddOp(v, OP_RowData, iCur, 0);    sqliteVdbeAddOp(v, OP_PutIntKey, oldIdx, 0);    /* Generate the NEW table    */    if( chngRecno ){      sqliteExprCode(pParse, pRecnoExpr);    }else{      sqliteVdbeAddOp(v, OP_Recno, iCur, 0);    }    for(i=0; i<pTab->nCol; i++){      if( i==pTab->iPKey ){        sqliteVdbeAddOp(v, OP_String, 0, 0);        continue;      }      j = aXRef[i];      if( j<0 ){        sqliteVdbeAddOp(v, OP_Column, iCur, i);      }else{        sqliteExprCode(pParse, pChanges->a[j].pExpr);      }    }    sqliteVdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);    sqliteVdbeAddOp(v, OP_PutIntKey, newIdx, 0);    if( !isView ){      sqliteVdbeAddOp(v, OP_Close, iCur, 0);    }    /* Fire the BEFORE and INSTEAD OF triggers    */    if( sqliteCodeRowTrigger(pParse, TK_UPDATE, pChanges, TK_BEFORE, pTab,           newIdx, oldIdx, onError, addr) ){      goto update_cleanup;    }  }  if( !isView ){    /*     ** Open every index that needs updating.  Note that if any    ** index could potentially invoke a REPLACE conflict resolution     ** action, then we need to open all indices because we might need    ** to be deleting some records.    */    sqliteVdbeAddOp(v, OP_Integer, pTab->iDb, 0);    sqliteVdbeAddOp(v, OP_OpenWrite, iCur, pTab->tnum);    if( onError==OE_Replace ){      openAll = 1;    }else{      openAll = 0;      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){        if( pIdx->onError==OE_Replace ){          openAll = 1;          break;        }      }    }    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){      if( openAll || aIdxUsed[i] ){        sqliteVdbeAddOp(v, OP_Integer, pIdx->iDb, 0);        sqliteVdbeAddOp(v, OP_OpenWrite, iCur+i+1, pIdx->tnum);        assert( pParse->nTab>iCur+i+1 );      }    }    /* Loop over every record that needs updating.  We have to load    ** the old data for each record to be updated because some columns    ** might not change and we will need to copy the old value.    ** Also, the old data is needed to delete the old index entires.    ** So make the cursor point at the old record.    */    if( !row_triggers_exist ){      sqliteVdbeAddOp(v, OP_ListRewind, 0, 0);      addr = sqliteVdbeAddOp(v, OP_ListRead, 0, 0);      sqliteVdbeAddOp(v, OP_Dup, 0, 0);    }    sqliteVdbeAddOp(v, OP_NotExists, iCur, addr);    /* If the record number will change, push the record number as it    ** will be after the update. (The old record number is currently    ** on top of the stack.)    */    if( chngRecno ){      sqliteExprCode(pParse, pRecnoExpr);      sqliteVdbeAddOp(v, OP_MustBeInt, 0, 0);    }    /* Compute new data for this record.      */    for(i=0; i<pTab->nCol; i++){      if( i==pTab->iPKey ){        sqliteVdbeAddOp(v, OP_String, 0, 0);        continue;      }      j = aXRef[i];      if( j<0 ){        sqliteVdbeAddOp(v, OP_Column, iCur, i);      }else{        sqliteExprCode(pParse, pChanges->a[j].pExpr);      }    }    /* Do constraint checks    */    sqliteGenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRecno, 1,                                   onError, addr);    /* Delete the old indices for the current record.    */    sqliteGenerateRowIndexDelete(db, v, pTab, iCur, aIdxUsed);    /* If changing the record number, delete the old record.    */    if( chngRecno ){      sqliteVdbeAddOp(v, OP_Delete, iCur, 0);    }    /* Create the new index entries and the new record.    */    sqliteCompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRecno, 1, -1);  }  /* Increment the row counter   */  if( db->flags & SQLITE_CountRows && !pParse->trigStack){    sqliteVdbeAddOp(v, OP_AddImm, 1, 0);  }  /* If there are triggers, close all the cursors after each iteration  ** through the loop.  The fire the after triggers.  */  if( row_triggers_exist ){    if( !isView ){      for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){        if( openAll || aIdxUsed[i] )          sqliteVdbeAddOp(v, OP_Close, iCur+i+1, 0);      }      sqliteVdbeAddOp(v, OP_Close, iCur, 0);      pParse->nTab = iCur;    }    if( sqliteCodeRowTrigger(pParse, TK_UPDATE, pChanges, TK_AFTER, pTab,           newIdx, oldIdx, onError, addr) ){      goto update_cleanup;    }  }  /* Repeat the above with the next record to be updated, until  ** all record selected by the WHERE clause have been updated.  */  sqliteVdbeAddOp(v, OP_Goto, 0, addr);  sqliteVdbeChangeP2(v, addr, sqliteVdbeCurrentAddr(v));  sqliteVdbeAddOp(v, OP_ListReset, 0, 0);  /* Close all tables if there were no FOR EACH ROW triggers */  if( !row_triggers_exist ){    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){      if( openAll || aIdxUsed[i] ){        sqliteVdbeAddOp(v, OP_Close, iCur+i+1, 0);      }    }    sqliteVdbeAddOp(v, OP_Close, iCur, 0);    pParse->nTab = iCur;  }else{    sqliteVdbeAddOp(v, OP_Close, newIdx, 0);    sqliteVdbeAddOp(v, OP_Close, oldIdx, 0);  }  sqliteVdbeAddOp(v, OP_SetCounts, 0, 0);  sqliteEndWriteOperation(pParse);  /*  ** Return the number of rows that were changed.  */  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){    sqliteVdbeOp3(v, OP_ColumnName, 0, 1, "rows updated", P3_STATIC);    sqliteVdbeAddOp(v, OP_Callback, 1, 0);  }update_cleanup:  sqliteAuthContextPop(&sContext);  sqliteFree(apIdx);  sqliteFree(aXRef);  sqliteSrcListDelete(pTabList);  sqliteExprListDelete(pChanges);  sqliteExprDelete(pWhere);  return;}