Ejemplo n.º 1
0
/*
** Process an UPDATE statement.
**
**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
**          \_______/ \________/     \______/       \________________/
*            onError   pTabList      pChanges             pWhere
*/
void sqlite3Update(
  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 = 0;          /* 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 */
  sqlite3 *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 = 0;  /* Expression defining the new record number */
  int openAll = 0;       /* True if all indices need to be opened */
  AuthContext sContext;  /* The authorization context */
  NameContext sNC;       /* The name-context to resolve expressions in */

#ifndef SQLITE_OMIT_TRIGGER
  int isView;                  /* Trying to update a view */
  int triggers_exist = 0;      /* True if any row triggers exist */
#endif

  int newIdx      = -1;  /* index of trigger "new" temp table       */
  int oldIdx      = -1;  /* index of trigger "old" temp table       */

  sContext.pParse = 0;
  if( pParse->nErr || sqlite3_malloc_failed ) goto update_cleanup;
  db = pParse->db;
  assert( pTabList->nSrc==1 );

  /* Locate the table which we want to update. 
  */
  pTab = sqlite3SrcListLookup(pParse, pTabList);
  if( pTab==0 ) goto update_cleanup;

  /* Figure out if we have any triggers and if the table being
  ** updated is a view
  */
#ifndef SQLITE_OMIT_TRIGGER
  triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_UPDATE, pChanges);
  isView = pTab->pSelect!=0;
#else
# define triggers_exist 0
# define isView 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

  if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
    goto update_cleanup;
  }
  if( isView ){
    if( sqlite3ViewGetColumnNames(pParse, pTab) ){
      goto update_cleanup;
    }
  }
  aXRef = sqliteMallocRaw( 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( 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++;
  }

  /* Initialize the name-context */
  memset(&sNC, 0, sizeof(sNC));
  sNC.pParse = pParse;
  sNC.pSrcList = pTabList;

  /* 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( sqlite3ExprResolveNames(&sNC, pChanges->a[i].pExpr) ){
      goto update_cleanup;
    }
    for(j=0; j<pTab->nCol; j++){
      if( sqlite3StrICmp(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( sqlite3IsRowid(pChanges->a[i].zName) ){
        chngRecno = 1;
        pRecnoExpr = pChanges->a[i].pExpr;
      }else{
        sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
        goto update_cleanup;
      }
    }
#ifndef SQLITE_OMIT_AUTHORIZATION
    {
      int rc;
      rc = sqlite3AuthCheck(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 = sqliteMallocRaw( 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 ){
      if( sqlite3CheckIndexCollSeq(pParse, pIdx) ) goto update_cleanup;
      apIdx[nIdx++] = pIdx;
      aIdxUsed[j] = 1;
    }else{
      aIdxUsed[j] = 0;
    }
  }

  /* Resolve the column names in all the expressions in the
  ** WHERE clause.
  */
  if( sqlite3ExprResolveNames(&sNC, pWhere) ){
    goto update_cleanup;
  }

  /* Start the view context
  */
  if( isView ){
    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
  }

  /* Begin generating code.
  */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto update_cleanup;
  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
  sqlite3BeginWriteOperation(pParse, 1, pTab->iDb);

  /* If we are trying to update a view, construct that view into
  ** a temporary table.
  */
  if( isView ){
    Select *pView;
    pView = sqlite3SelectDup(pTab->pSelect);
    sqlite3Select(pParse, pView, SRT_TempTable, iCur, 0, 0, 0, 0);
    sqlite3SelectDelete(pView);
  }

  /* Begin the database scan
  */
  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0, 0);
  if( pWInfo==0 ) goto update_cleanup;

  /* Remember the index of every item to be updated.
  */
  sqlite3VdbeAddOp(v, OP_Recno, iCur, 0);
  sqlite3VdbeAddOp(v, OP_ListWrite, 0, 0);

  /* End the database scan loop.
  */
  sqlite3WhereEnd(pWInfo);

  /* Initialize the count of updated rows
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
    sqlite3VdbeAddOp(v, OP_Integer, 0, 0);
  }

  if( triggers_exist ){
    /* Create pseudo-tables for NEW and OLD
    */
    sqlite3VdbeAddOp(v, OP_OpenPseudo, oldIdx, 0);
    sqlite3VdbeAddOp(v, OP_SetNumColumns, oldIdx, pTab->nCol);
    sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);
    sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);

    /* The top of the update loop for when there are triggers.
    */
    sqlite3VdbeAddOp(v, OP_ListRewind, 0, 0);
    addr = sqlite3VdbeAddOp(v, OP_ListRead, 0, 0);
    sqlite3VdbeAddOp(v, OP_Dup, 0, 0);

    /* Open a cursor and make it point to the record that is
    ** being updated.
    */
    sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
    if( !isView ){
      sqlite3OpenTableForReading(v, iCur, pTab);
    }
    sqlite3VdbeAddOp(v, OP_MoveGe, iCur, 0);

    /* Generate the OLD table
    */
    sqlite3VdbeAddOp(v, OP_Recno, iCur, 0);
    sqlite3VdbeAddOp(v, OP_RowData, iCur, 0);
    sqlite3VdbeAddOp(v, OP_PutIntKey, oldIdx, 0);

    /* Generate the NEW table
    */
    if( chngRecno ){
      sqlite3ExprCodeAndCache(pParse, pRecnoExpr);
    }else{
      sqlite3VdbeAddOp(v, OP_Recno, iCur, 0);
    }
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp(v, OP_String8, 0, 0);
        continue;
      }
      j = aXRef[i];
      if( j<0 ){
        sqlite3VdbeAddOp(v, OP_Column, iCur, i);
        sqlite3ColumnDefault(v, pTab, i);
      }else{
        sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr);
      }
    }
    sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);
    if( !isView ){
      sqlite3TableAffinityStr(v, pTab);
    }
    if( pParse->nErr ) goto update_cleanup;
    sqlite3VdbeAddOp(v, OP_PutIntKey, newIdx, 0);
    if( !isView ){
      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
    }

    /* Fire the BEFORE and INSTEAD OF triggers
    */
    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_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.
    */
    sqlite3VdbeAddOp(v, OP_Integer, pTab->iDb, 0);
    sqlite3VdbeAddOp(v, OP_OpenWrite, iCur, pTab->tnum);
    sqlite3VdbeAddOp(v, OP_SetNumColumns, iCur, pTab->nCol);
    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] ){
        sqlite3VdbeAddOp(v, OP_Integer, pIdx->iDb, 0);
        sqlite3VdbeOp3(v, OP_OpenWrite, iCur+i+1, pIdx->tnum,
                       (char*)&pIdx->keyInfo, P3_KEYINFO);
        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( !triggers_exist ){
      sqlite3VdbeAddOp(v, OP_ListRewind, 0, 0);
      addr = sqlite3VdbeAddOp(v, OP_ListRead, 0, 0);
      sqlite3VdbeAddOp(v, OP_Dup, 0, 0);
    }
    sqlite3VdbeAddOp(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 ){
      sqlite3ExprCode(pParse, pRecnoExpr);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
    }

    /* Compute new data for this record.  
    */
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp(v, OP_String8, 0, 0);
        continue;
      }
      j = aXRef[i];
      if( j<0 ){
        sqlite3VdbeAddOp(v, OP_Column, iCur, i);
        sqlite3ColumnDefault(v, pTab, i);
      }else{
        sqlite3ExprCode(pParse, pChanges->a[j].pExpr);
      }
    }

    /* Do constraint checks
    */
    sqlite3GenerateConstraintChecks(pParse, pTab, iCur, aIdxUsed, chngRecno, 1,
                                   onError, addr);

    /* Delete the old indices for the current record.
    */
    sqlite3GenerateRowIndexDelete(db, v, pTab, iCur, aIdxUsed);

    /* If changing the record number, delete the old record.
    */
    if( chngRecno ){
      sqlite3VdbeAddOp(v, OP_Delete, iCur, 0);
    }

    /* Create the new index entries and the new record.
    */
    sqlite3CompleteInsertion(pParse, pTab, iCur, aIdxUsed, chngRecno, 1, -1);
  }

  /* Increment the row counter 
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack){
    sqlite3VdbeAddOp(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( triggers_exist ){
    if( !isView ){
      for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
        if( openAll || aIdxUsed[i] )
          sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
      }
      sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
    }
    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_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.
  */
  sqlite3VdbeAddOp(v, OP_Goto, 0, addr);
  sqlite3VdbeChangeP2(v, addr, sqlite3VdbeCurrentAddr(v));
  sqlite3VdbeAddOp(v, OP_ListReset, 0, 0);

  /* Close all tables if there were no FOR EACH ROW triggers */
  if( !triggers_exist ){
    for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
      if( openAll || aIdxUsed[i] ){
        sqlite3VdbeAddOp(v, OP_Close, iCur+i+1, 0);
      }
    }
    sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
  }else{
    sqlite3VdbeAddOp(v, OP_Close, newIdx, 0);
    sqlite3VdbeAddOp(v, OP_Close, oldIdx, 0);
  }

  /*
  ** Return the number of rows that were changed. If this routine is 
  ** generating code because of a call to sqlite3NestedParse(), do not
  ** invoke the callback function.
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
    sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
    sqlite3VdbeSetNumCols(v, 1);
    sqlite3VdbeSetColName(v, 0, "rows updated", P3_STATIC);
  }

update_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqliteFree(apIdx);
  sqliteFree(aXRef);
  sqlite3SrcListDelete(pTabList);
  sqlite3ExprListDelete(pChanges);
  sqlite3ExprDelete(pWhere);
  return;
}
Ejemplo n.º 2
0
/*
** This routine is call to handle SQL of the following forms:
**
**    insert into TABLE (IDLIST) values(EXPRLIST)
**    insert into TABLE (IDLIST) select
**
** The IDLIST following the table name is always optional.  If omitted,
** then a list of all columns for the table is substituted.  The IDLIST
** appears in the pColumn parameter.  pColumn is NULL if IDLIST is omitted.
**
** The pList parameter holds EXPRLIST in the first form of the INSERT
** statement above, and pSelect is NULL.  For the second form, pList is
** NULL and pSelect is a pointer to the select statement used to generate
** data for the insert.
**
** The code generated follows one of three templates.  For a simple
** select with data coming from a VALUES clause, the code executes
** once straight down through.  The template looks like this:
**
**         open write cursor to <table> and its indices
**         puts VALUES clause expressions onto the stack
**         write the resulting record into <table>
**         cleanup
**
** If the statement is of the form
**
**   INSERT INTO <table> SELECT ...
**
** And the SELECT clause does not read from <table> at any time, then
** the generated code follows this template:
**
**         goto B
**      A: setup for the SELECT
**         loop over the tables in the SELECT
**           gosub C
**         end loop
**         cleanup after the SELECT
**         goto D
**      B: open write cursor to <table> and its indices
**         goto A
**      C: insert the select result into <table>
**         return
**      D: cleanup
**
** The third template is used if the insert statement takes its
** values from a SELECT but the data is being inserted into a table
** that is also read as part of the SELECT.  In the third form,
** we have to use a intermediate table to store the results of
** the select.  The template is like this:
**
**         goto B
**      A: setup for the SELECT
**         loop over the tables in the SELECT
**           gosub C
**         end loop
**         cleanup after the SELECT
**         goto D
**      C: insert the select result into the intermediate table
**         return
**      B: open a cursor to an intermediate table
**         goto A
**      D: open write cursor to <table> and its indices
**         loop over the intermediate table
**           transfer values form intermediate table into <table>
**         end the loop
**         cleanup
*/
void sqlite3Insert(
  Parse *pParse,        /* Parser context */
  SrcList *pTabList,    /* Name of table into which we are inserting */
  ExprList *pList,      /* List of values to be inserted */
  Select *pSelect,      /* A SELECT statement to use as the data source */
  IdList *pColumn,      /* Column names corresponding to IDLIST. */
  int onError           /* How to handle constraint errors */
){
  Table *pTab;          /* The table to insert into */
  char *zTab;           /* Name of the table into which we are inserting */
  const char *zDb;      /* Name of the database holding this table */
  int i, j, idx;        /* Loop counters */
  Vdbe *v;              /* Generate code into this virtual machine */
  Index *pIdx;          /* For looping over indices of the table */
  int nColumn;          /* Number of columns in the data */
  int base = 0;         /* VDBE Cursor number for pTab */
  int iCont=0,iBreak=0; /* Beginning and end of the loop over srcTab */
  sqlite3 *db;          /* The main database structure */
  int keyColumn = -1;   /* Column that is the INTEGER PRIMARY KEY */
  int endOfLoop;        /* Label for the end of the insertion loop */
  int useTempTable = 0; /* Store SELECT results in intermediate table */
  int srcTab = 0;       /* Data comes from this temporary cursor if >=0 */
  int iSelectLoop = 0;  /* Address of code that implements the SELECT */
  int iCleanup = 0;     /* Address of the cleanup code */
  int iInsertBlock = 0; /* Address of the subroutine used to insert data */
  int iCntMem = 0;      /* Memory cell used for the row counter */
  int newIdx = -1;      /* Cursor for the NEW table */
  Db *pDb;              /* The database containing table being inserted into */
  int counterMem = 0;   /* Memory cell holding AUTOINCREMENT counter */
  int iDb;

#ifndef SQLITE_OMIT_TRIGGER
  int isView;                 /* True if attempting to insert into a view */
  int triggers_exist = 0;     /* True if there are FOR EACH ROW triggers */
#endif

#ifndef SQLITE_OMIT_AUTOINCREMENT
  int counterRowid = 0;  /* Memory cell holding rowid of autoinc counter */
#endif

  if( pParse->nErr || sqlite3MallocFailed() ){
    goto insert_cleanup;
  }
  db = pParse->db;

  /* Locate the table into which we will be inserting new information.
  */
  assert( pTabList->nSrc==1 );
  zTab = pTabList->a[0].zName;
  if( zTab==0 ) goto insert_cleanup;
  pTab = sqlite3SrcListLookup(pParse, pTabList);
  if( pTab==0 ){
    goto insert_cleanup;
  }
  iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
  assert( iDb<db->nDb );
  pDb = &db->aDb[iDb];
  zDb = pDb->zName;
  if( sqlite3AuthCheck(pParse, SQLITE_INSERT, pTab->zName, 0, zDb) ){
    goto insert_cleanup;
  }

  /* Figure out if we have any triggers and if the table being
  ** inserted into is a view
  */
#ifndef SQLITE_OMIT_TRIGGER
  triggers_exist = sqlite3TriggersExist(pParse, pTab, TK_INSERT, 0);
  isView = pTab->pSelect!=0;
#else
# define triggers_exist 0
# define isView 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

  /* Ensure that:
  *  (a) the table is not read-only, 
  *  (b) that if it is a view then ON INSERT triggers exist
  */
  if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
    goto insert_cleanup;
  }
  assert( pTab!=0 );

  /* If pTab is really a view, make sure it has been initialized.
  */
  if( isView && sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto insert_cleanup;
  }

  /* Allocate a VDBE
  */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto insert_cleanup;
  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
  sqlite3BeginWriteOperation(pParse, pSelect || triggers_exist, iDb);

  /* if there are row triggers, allocate a temp table for new.* references. */
  if( triggers_exist ){
    newIdx = pParse->nTab++;
  }

#ifndef SQLITE_OMIT_AUTOINCREMENT
  /* If this is an AUTOINCREMENT table, look up the sequence number in the
  ** sqlite_sequence table and store it in memory cell counterMem.  Also
  ** remember the rowid of the sqlite_sequence table entry in memory cell
  ** counterRowid.
  */
  if( pTab->autoInc ){
    int iCur = pParse->nTab;
    int addr = sqlite3VdbeCurrentAddr(v);
    counterRowid = pParse->nMem++;
    counterMem = pParse->nMem++;
    sqlite3OpenTable(pParse, iCur, iDb, pDb->pSchema->pSeqTab, OP_OpenRead);
    sqlite3VdbeAddOp(v, OP_Rewind, iCur, addr+13);
    sqlite3VdbeAddOp(v, OP_Column, iCur, 0);
    sqlite3VdbeOp3(v, OP_String8, 0, 0, pTab->zName, 0);
    sqlite3VdbeAddOp(v, OP_Ne, 0x100, addr+12);
    sqlite3VdbeAddOp(v, OP_Rowid, iCur, 0);
    sqlite3VdbeAddOp(v, OP_MemStore, counterRowid, 1);
    sqlite3VdbeAddOp(v, OP_Column, iCur, 1);
    sqlite3VdbeAddOp(v, OP_MemStore, counterMem, 1);
    sqlite3VdbeAddOp(v, OP_Goto, 0, addr+13);
    sqlite3VdbeAddOp(v, OP_Next, iCur, addr+4);
    sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
  }
#endif /* SQLITE_OMIT_AUTOINCREMENT */

  /* Figure out how many columns of data are supplied.  If the data
  ** is coming from a SELECT statement, then this step also generates
  ** all the code to implement the SELECT statement and invoke a subroutine
  ** to process each row of the result. (Template 2.) If the SELECT
  ** statement uses the the table that is being inserted into, then the
  ** subroutine is also coded here.  That subroutine stores the SELECT
  ** results in a temporary table. (Template 3.)
  */
  if( pSelect ){
    /* Data is coming from a SELECT.  Generate code to implement that SELECT
    */
    int rc, iInitCode;
    iInitCode = sqlite3VdbeAddOp(v, OP_Goto, 0, 0);
    iSelectLoop = sqlite3VdbeCurrentAddr(v);
    iInsertBlock = sqlite3VdbeMakeLabel(v);

    /* Resolve the expressions in the SELECT statement and execute it. */
    rc = sqlite3Select(pParse, pSelect, SRT_Subroutine, iInsertBlock,0,0,0,0);
    if( rc || pParse->nErr || sqlite3MallocFailed() ){
      goto insert_cleanup;
    }

    iCleanup = sqlite3VdbeMakeLabel(v);
    sqlite3VdbeAddOp(v, OP_Goto, 0, iCleanup);
    assert( pSelect->pEList );
    nColumn = pSelect->pEList->nExpr;

    /* Set useTempTable to TRUE if the result of the SELECT statement
    ** should be written into a temporary table.  Set to FALSE if each
    ** row of the SELECT can be written directly into the result table.
    **
    ** A temp table must be used if the table being updated is also one
    ** of the tables being read by the SELECT statement.  Also use a 
    ** temp table in the case of row triggers.
    */
    if( triggers_exist || selectReadsTable(pSelect,pTab->pSchema,pTab->tnum) ){
      useTempTable = 1;
    }

    if( useTempTable ){
      /* Generate the subroutine that SELECT calls to process each row of
      ** the result.  Store the result in a temporary table
      */
      srcTab = pParse->nTab++;
      sqlite3VdbeResolveLabel(v, iInsertBlock);
      sqlite3VdbeAddOp(v, OP_MakeRecord, nColumn, 0);
      sqlite3VdbeAddOp(v, OP_NewRowid, srcTab, 0);
      sqlite3VdbeAddOp(v, OP_Pull, 1, 0);
      sqlite3VdbeAddOp(v, OP_Insert, srcTab, 0);
      sqlite3VdbeAddOp(v, OP_Return, 0, 0);

      /* The following code runs first because the GOTO at the very top
      ** of the program jumps to it.  Create the temporary table, then jump
      ** back up and execute the SELECT code above.
      */
      sqlite3VdbeJumpHere(v, iInitCode);
      sqlite3VdbeAddOp(v, OP_OpenVirtual, srcTab, 0);
      sqlite3VdbeAddOp(v, OP_SetNumColumns, srcTab, nColumn);
      sqlite3VdbeAddOp(v, OP_Goto, 0, iSelectLoop);
      sqlite3VdbeResolveLabel(v, iCleanup);
    }else{
      sqlite3VdbeJumpHere(v, iInitCode);
    }
  }else{
    /* This is the case if the data for the INSERT is coming from a VALUES
    ** clause
    */
    NameContext sNC;
    memset(&sNC, 0, sizeof(sNC));
    sNC.pParse = pParse;
    assert( pList!=0 );
    srcTab = -1;
    useTempTable = 0;
    assert( pList );
    nColumn = pList->nExpr;
    for(i=0; i<nColumn; i++){
      if( sqlite3ExprResolveNames(&sNC, pList->a[i].pExpr) ){
        goto insert_cleanup;
      }
    }
  }

  /* Make sure the number of columns in the source data matches the number
  ** of columns to be inserted into the table.
  */
  if( pColumn==0 && nColumn!=pTab->nCol ){
    sqlite3ErrorMsg(pParse, 
       "table %S has %d columns but %d values were supplied",
       pTabList, 0, pTab->nCol, nColumn);
    goto insert_cleanup;
  }
  if( pColumn!=0 && nColumn!=pColumn->nId ){
    sqlite3ErrorMsg(pParse, "%d values for %d columns", nColumn, pColumn->nId);
    goto insert_cleanup;
  }

  /* If the INSERT statement included an IDLIST term, then make sure
  ** all elements of the IDLIST really are columns of the table and 
  ** remember the column indices.
  **
  ** If the table has an INTEGER PRIMARY KEY column and that column
  ** is named in the IDLIST, then record in the keyColumn variable
  ** the index into IDLIST of the primary key column.  keyColumn is
  ** the index of the primary key as it appears in IDLIST, not as
  ** is appears in the original table.  (The index of the primary
  ** key in the original table is pTab->iPKey.)
  */
  if( pColumn ){
    for(i=0; i<pColumn->nId; i++){
      pColumn->a[i].idx = -1;
    }
    for(i=0; i<pColumn->nId; i++){
      for(j=0; j<pTab->nCol; j++){
        if( sqlite3StrICmp(pColumn->a[i].zName, pTab->aCol[j].zName)==0 ){
          pColumn->a[i].idx = j;
          if( j==pTab->iPKey ){
            keyColumn = i;
          }
          break;
        }
      }
      if( j>=pTab->nCol ){
        if( sqlite3IsRowid(pColumn->a[i].zName) ){
          keyColumn = i;
        }else{
          sqlite3ErrorMsg(pParse, "table %S has no column named %s",
              pTabList, 0, pColumn->a[i].zName);
          pParse->nErr++;
          goto insert_cleanup;
        }
      }
    }
  }

  /* If there is no IDLIST term but the table has an integer primary
  ** key, the set the keyColumn variable to the primary key column index
  ** in the original table definition.
  */
  if( pColumn==0 ){
    keyColumn = pTab->iPKey;
  }

  /* Open the temp table for FOR EACH ROW triggers
  */
  if( triggers_exist ){
    sqlite3VdbeAddOp(v, OP_OpenPseudo, newIdx, 0);
    sqlite3VdbeAddOp(v, OP_SetNumColumns, newIdx, pTab->nCol);
  }
    
  /* Initialize the count of rows to be inserted
  */
  if( db->flags & SQLITE_CountRows ){
    iCntMem = pParse->nMem++;
    sqlite3VdbeAddOp(v, OP_MemInt, 0, iCntMem);
  }

  /* Open tables and indices if there are no row triggers */
  if( !triggers_exist ){
    base = pParse->nTab;
    sqlite3OpenTableAndIndices(pParse, pTab, base, OP_OpenWrite);
  }

  /* If the data source is a temporary table, then we have to create
  ** a loop because there might be multiple rows of data.  If the data
  ** source is a subroutine call from the SELECT statement, then we need
  ** to launch the SELECT statement processing.
  */
  if( useTempTable ){
    iBreak = sqlite3VdbeMakeLabel(v);
    sqlite3VdbeAddOp(v, OP_Rewind, srcTab, iBreak);
    iCont = sqlite3VdbeCurrentAddr(v);
  }else if( pSelect ){
    sqlite3VdbeAddOp(v, OP_Goto, 0, iSelectLoop);
    sqlite3VdbeResolveLabel(v, iInsertBlock);
  }

  /* Run the BEFORE and INSTEAD OF triggers, if there are any
  */
  endOfLoop = sqlite3VdbeMakeLabel(v);
  if( triggers_exist & TRIGGER_BEFORE ){

    /* build the NEW.* reference row.  Note that if there is an INTEGER
    ** PRIMARY KEY into which a NULL is being inserted, that NULL will be
    ** translated into a unique ID for the row.  But on a BEFORE trigger,
    ** we do not know what the unique ID will be (because the insert has
    ** not happened yet) so we substitute a rowid of -1
    */
    if( keyColumn<0 ){
      sqlite3VdbeAddOp(v, OP_Integer, -1, 0);
    }else if( useTempTable ){
      sqlite3VdbeAddOp(v, OP_Column, srcTab, keyColumn);
    }else{
      assert( pSelect==0 );  /* Otherwise useTempTable is true */
      sqlite3ExprCode(pParse, pList->a[keyColumn].pExpr);
      sqlite3VdbeAddOp(v, OP_NotNull, -1, sqlite3VdbeCurrentAddr(v)+3);
      sqlite3VdbeAddOp(v, OP_Pop, 1, 0);
      sqlite3VdbeAddOp(v, OP_Integer, -1, 0);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
    }

    /* Create the new column data
    */
    for(i=0; i<pTab->nCol; i++){
      if( pColumn==0 ){
        j = i;
      }else{
        for(j=0; j<pColumn->nId; j++){
          if( pColumn->a[j].idx==i ) break;
        }
      }
      if( pColumn && j>=pColumn->nId ){
        sqlite3ExprCode(pParse, pTab->aCol[i].pDflt);
      }else if( useTempTable ){
        sqlite3VdbeAddOp(v, OP_Column, srcTab, j); 
      }else{
        assert( pSelect==0 ); /* Otherwise useTempTable is true */
        sqlite3ExprCodeAndCache(pParse, pList->a[j].pExpr);
      }
    }
    sqlite3VdbeAddOp(v, OP_MakeRecord, pTab->nCol, 0);

    /* If this is an INSERT on a view with an INSTEAD OF INSERT trigger,
    ** do not attempt any conversions before assembling the record.
    ** If this is a real table, attempt conversions as required by the
    ** table column affinities.
    */
    if( !isView ){
      sqlite3TableAffinityStr(v, pTab);
    }
    sqlite3VdbeAddOp(v, OP_Insert, newIdx, 0);

    /* Fire BEFORE or INSTEAD OF triggers */
    if( sqlite3CodeRowTrigger(pParse, TK_INSERT, 0, TRIGGER_BEFORE, pTab, 
        newIdx, -1, onError, endOfLoop) ){
      goto insert_cleanup;
    }
  }

  /* If any triggers exists, the opening of tables and indices is deferred
  ** until now.
  */
  if( triggers_exist && !isView ){
    base = pParse->nTab;
    sqlite3OpenTableAndIndices(pParse, pTab, base, OP_OpenWrite);
  }

  /* Push the record number for the new entry onto the stack.  The
  ** record number is a randomly generate integer created by NewRowid
  ** except when the table has an INTEGER PRIMARY KEY column, in which
  ** case the record number is the same as that column. 
  */
  if( !isView ){
    if( keyColumn>=0 ){
      if( useTempTable ){
        sqlite3VdbeAddOp(v, OP_Column, srcTab, keyColumn);
      }else if( pSelect ){
        sqlite3VdbeAddOp(v, OP_Dup, nColumn - keyColumn - 1, 1);
      }else{
        sqlite3ExprCode(pParse, pList->a[keyColumn].pExpr);
      }
      /* If the PRIMARY KEY expression is NULL, then use OP_NewRowid
      ** to generate a unique primary key value.
      */
      sqlite3VdbeAddOp(v, OP_NotNull, -1, sqlite3VdbeCurrentAddr(v)+3);
      sqlite3VdbeAddOp(v, OP_Pop, 1, 0);
      sqlite3VdbeAddOp(v, OP_NewRowid, base, counterMem);
      sqlite3VdbeAddOp(v, OP_MustBeInt, 0, 0);
    }else{
      sqlite3VdbeAddOp(v, OP_NewRowid, base, counterMem);
    }
#ifndef SQLITE_OMIT_AUTOINCREMENT
    if( pTab->autoInc ){
      sqlite3VdbeAddOp(v, OP_MemMax, counterMem, 0);
    }
#endif /* SQLITE_OMIT_AUTOINCREMENT */

    /* Push onto the stack, data for all columns of the new entry, beginning
    ** with the first column.
    */
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        /* The value of the INTEGER PRIMARY KEY column is always a NULL.
        ** Whenever this column is read, the record number will be substituted
        ** in its place.  So will fill this column with a NULL to avoid
        ** taking up data space with information that will never be used. */
        sqlite3VdbeAddOp(v, OP_Null, 0, 0);
        continue;
      }
      if( pColumn==0 ){
        j = i;
      }else{
        for(j=0; j<pColumn->nId; j++){
          if( pColumn->a[j].idx==i ) break;
        }
      }
      if( pColumn && j>=pColumn->nId ){
        sqlite3ExprCode(pParse, pTab->aCol[i].pDflt);
      }else if( useTempTable ){
        sqlite3VdbeAddOp(v, OP_Column, srcTab, j); 
      }else if( pSelect ){
        sqlite3VdbeAddOp(v, OP_Dup, i+nColumn-j, 1);
      }else{
        sqlite3ExprCode(pParse, pList->a[j].pExpr);
      }
    }

    /* Generate code to check constraints and generate index keys and
    ** do the insertion.
    */
    sqlite3GenerateConstraintChecks(pParse, pTab, base, 0, keyColumn>=0,
                                   0, onError, endOfLoop);
    sqlite3CompleteInsertion(pParse, pTab, base, 0,0,0,
                            (triggers_exist & TRIGGER_AFTER)!=0 ? newIdx : -1);
  }

  /* Update the count of rows that are inserted
  */
  if( (db->flags & SQLITE_CountRows)!=0 ){
    sqlite3VdbeAddOp(v, OP_MemIncr, 1, iCntMem);
  }

  if( triggers_exist ){
    /* Close all tables opened */
    if( !isView ){
      sqlite3VdbeAddOp(v, OP_Close, base, 0);
      for(idx=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, idx++){
        sqlite3VdbeAddOp(v, OP_Close, idx+base, 0);
      }
    }

    /* Code AFTER triggers */
    if( sqlite3CodeRowTrigger(pParse, TK_INSERT, 0, TRIGGER_AFTER, pTab,
          newIdx, -1, onError, endOfLoop) ){
      goto insert_cleanup;
    }
  }

  /* The bottom of the loop, if the data source is a SELECT statement
  */
  sqlite3VdbeResolveLabel(v, endOfLoop);
  if( useTempTable ){
    sqlite3VdbeAddOp(v, OP_Next, srcTab, iCont);
    sqlite3VdbeResolveLabel(v, iBreak);
    sqlite3VdbeAddOp(v, OP_Close, srcTab, 0);
  }else if( pSelect ){
    sqlite3VdbeAddOp(v, OP_Pop, nColumn, 0);
    sqlite3VdbeAddOp(v, OP_Return, 0, 0);
    sqlite3VdbeResolveLabel(v, iCleanup);
  }

  if( !triggers_exist ){
    /* Close all tables opened */
    sqlite3VdbeAddOp(v, OP_Close, base, 0);
    for(idx=1, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, idx++){
      sqlite3VdbeAddOp(v, OP_Close, idx+base, 0);
    }
  }

#ifndef SQLITE_OMIT_AUTOINCREMENT
  /* Update the sqlite_sequence table by storing the content of the
  ** counter value in memory counterMem back into the sqlite_sequence
  ** table.
  */
  if( pTab->autoInc ){
    int iCur = pParse->nTab;
    int addr = sqlite3VdbeCurrentAddr(v);
    sqlite3OpenTable(pParse, iCur, iDb, pDb->pSchema->pSeqTab, OP_OpenWrite);
    sqlite3VdbeAddOp(v, OP_MemLoad, counterRowid, 0);
    sqlite3VdbeAddOp(v, OP_NotNull, -1, addr+7);
    sqlite3VdbeAddOp(v, OP_Pop, 1, 0);
    sqlite3VdbeAddOp(v, OP_NewRowid, iCur, 0);
    sqlite3VdbeOp3(v, OP_String8, 0, 0, pTab->zName, 0);
    sqlite3VdbeAddOp(v, OP_MemLoad, counterMem, 0);
    sqlite3VdbeAddOp(v, OP_MakeRecord, 2, 0);
    sqlite3VdbeAddOp(v, OP_Insert, iCur, 0);
    sqlite3VdbeAddOp(v, OP_Close, iCur, 0);
  }
#endif

  /*
  ** Return the number of rows inserted. If this routine is 
  ** generating code because of a call to sqlite3NestedParse(), do not
  ** invoke the callback function.
  */
  if( db->flags & SQLITE_CountRows && pParse->nested==0 && !pParse->trigStack ){
    sqlite3VdbeAddOp(v, OP_MemLoad, iCntMem, 0);
    sqlite3VdbeAddOp(v, OP_Callback, 1, 0);
    sqlite3VdbeSetNumCols(v, 1);
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows inserted", P3_STATIC);
  }

insert_cleanup:
  sqlite3SrcListDelete(pTabList);
  sqlite3ExprListDelete(pList);
  sqlite3SelectDelete(pSelect);
  sqlite3IdListDelete(pColumn);
}
Ejemplo n.º 3
0
/*
** Process an UPDATE statement.
**
**   UPDATE OR IGNORE table_wxyz SET a=b, c=d WHERE e<5 AND f NOT NULL;
**          \_______/ \________/     \______/       \________________/
*            onError   pTabList      pChanges             pWhere
*/
void sqlite3Update(
  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 = 0;          /* 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 iCur;              /* VDBE Cursor number of pTab */
  sqlite3 *db;           /* The database structure */
  int *aRegIdx = 0;      /* One register assigned to each index to be updated */
  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 chngRowid;         /* True if the record number is being changed */
  Expr *pRowidExpr = 0;  /* Expression defining the new record number */
  int openAll = 0;       /* True if all indices need to be opened */
  AuthContext sContext;  /* The authorization context */
  NameContext sNC;       /* The name-context to resolve expressions in */
  int iDb;               /* Database containing the table being updated */
  int j1;                /* Addresses of jump instructions */
  int okOnePass;         /* True for one-pass algorithm without the FIFO */

#ifndef SQLITE_OMIT_TRIGGER
  int isView;                  /* Trying to update a view */
  int triggers_exist = 0;      /* True if any row triggers exist */
#endif
  int iBeginAfterTrigger = 0;  /* Address of after trigger program */
  int iEndAfterTrigger = 0;    /* Exit of after trigger program */
  int iBeginBeforeTrigger = 0; /* Address of before trigger program */
  int iEndBeforeTrigger = 0;   /* Exit of before trigger program */
  u32 old_col_mask = 0;        /* Mask of OLD.* columns in use */
  u32 new_col_mask = 0;        /* Mask of NEW.* columns in use */

  int newIdx      = -1;  /* index of trigger "new" temp table       */
  int oldIdx      = -1;  /* index of trigger "old" temp table       */

  /* Register Allocations */
  int regRowCount = 0;   /* A count of rows changed */
  int regOldRowid;       /* The old rowid */
  int regNewRowid;       /* The new rowid */
  int regData;           /* New data for the row */
  int regRowSet = 0;     /* Rowset of rows to be updated */

  sContext.pParse = 0;
  db = pParse->db;
  if( pParse->nErr || db->mallocFailed ){
    goto update_cleanup;
  }
  assert( pTabList->nSrc==1 );

  /* Locate the table which we want to update. 
  */
  pTab = sqlite3SrcListLookup(pParse, pTabList);
  if( pTab==0 ) goto update_cleanup;
  iDb = sqlite3SchemaToIndex(pParse->db, pTab->pSchema);

  /* Figure out if we have any triggers and if the table being
  ** updated is a view
  */
#ifndef SQLITE_OMIT_TRIGGER
  triggers_exist = sqlite3TriggersExist(pTab, TK_UPDATE, pChanges);
  isView = pTab->pSelect!=0;
#else
# define triggers_exist 0
# define isView 0
#endif
#ifdef SQLITE_OMIT_VIEW
# undef isView
# define isView 0
#endif

  if( sqlite3IsReadOnly(pParse, pTab, triggers_exist) ){
    goto update_cleanup;
  }
  if( sqlite3ViewGetColumnNames(pParse, pTab) ){
    goto update_cleanup;
  }
  aXRef = sqlite3DbMallocRaw(db, 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( 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++;
  }

  /* Initialize the name-context */
  memset(&sNC, 0, sizeof(sNC));
  sNC.pParse = pParse;
  sNC.pSrcList = pTabList;

  /* 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.
  */
  chngRowid = 0;
  for(i=0; i<pChanges->nExpr; i++){
    if( sqlite3ResolveExprNames(&sNC, pChanges->a[i].pExpr) ){
      goto update_cleanup;
    }
    for(j=0; j<pTab->nCol; j++){
      if( sqlite3StrICmp(pTab->aCol[j].zName, pChanges->a[i].zName)==0 ){
        if( j==pTab->iPKey ){
          chngRowid = 1;
          pRowidExpr = pChanges->a[i].pExpr;
        }
        aXRef[j] = i;
        break;
      }
    }
    if( j>=pTab->nCol ){
      if( sqlite3IsRowid(pChanges->a[i].zName) ){
        chngRowid = 1;
        pRowidExpr = pChanges->a[i].pExpr;
      }else{
        sqlite3ErrorMsg(pParse, "no such column: %s", pChanges->a[i].zName);
        goto update_cleanup;
      }
    }
#ifndef SQLITE_OMIT_AUTHORIZATION
    {
      int rc;
      rc = sqlite3AuthCheck(pParse, SQLITE_UPDATE, pTab->zName,
                           pTab->aCol[j].zName, db->aDb[iDb].zName);
      if( rc==SQLITE_DENY ){
        goto update_cleanup;
      }else if( rc==SQLITE_IGNORE ){
        aXRef[j] = -1;
      }
    }
#endif
  }

  /* Allocate memory for the array aRegIdx[].  There is one entry in the
  ** array for each index associated with table being updated.  Fill in
  ** the value with a register number for indices that are to be used
  ** and with zero for unused indices.
  */
  for(nIdx=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, nIdx++){}
  if( nIdx>0 ){
    aRegIdx = sqlite3DbMallocRaw(db, sizeof(Index*) * nIdx );
    if( aRegIdx==0 ) goto update_cleanup;
  }
  for(j=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, j++){
    int reg;
    if( chngRowid ){
      reg = ++pParse->nMem;
    }else{
      reg = 0;
      for(i=0; i<pIdx->nColumn; i++){
        if( aXRef[pIdx->aiColumn[i]]>=0 ){
          reg = ++pParse->nMem;
          break;
        }
      }
    }
    aRegIdx[j] = reg;
  }

  /* Allocate a block of register used to store the change record
  ** sent to sqlite3GenerateConstraintChecks().  There are either
  ** one or two registers for holding the rowid.  One rowid register
  ** is used if chngRowid is false and two are used if chngRowid is
  ** true.  Following these are pTab->nCol register holding column
  ** data.
  */
  regOldRowid = regNewRowid = pParse->nMem + 1;
  pParse->nMem += pTab->nCol + 1;
  if( chngRowid ){
    regNewRowid++;
    pParse->nMem++;
  }
  regData = regNewRowid+1;
 

  /* Begin generating code.
  */
  v = sqlite3GetVdbe(pParse);
  if( v==0 ) goto update_cleanup;
  if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
  sqlite3BeginWriteOperation(pParse, 1, iDb);

#ifndef SQLITE_OMIT_VIRTUALTABLE
  /* Virtual tables must be handled separately */
  if( IsVirtual(pTab) ){
    updateVirtualTable(pParse, pTabList, pTab, pChanges, pRowidExpr, aXRef,
                       pWhere);
    pWhere = 0;
    pTabList = 0;
    goto update_cleanup;
  }
#endif

  /* Start the view context
  */
  if( isView ){
    sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
  }

  /* Generate the code for triggers.
  */
  if( triggers_exist ){
    int iGoto;

    /* Create pseudo-tables for NEW and OLD
    */
    sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
    sqlite3VdbeAddOp2(v, OP_OpenPseudo, oldIdx, 0);
    sqlite3VdbeAddOp2(v, OP_SetNumColumns, 0, pTab->nCol);
    sqlite3VdbeAddOp2(v, OP_OpenPseudo, newIdx, 0);

    iGoto = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
    addr = sqlite3VdbeMakeLabel(v);
    iBeginBeforeTrigger = sqlite3VdbeCurrentAddr(v);
    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_BEFORE, pTab,
          newIdx, oldIdx, onError, addr, &old_col_mask, &new_col_mask) ){
      goto update_cleanup;
    }
    iEndBeforeTrigger = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
    iBeginAfterTrigger = sqlite3VdbeCurrentAddr(v);
    if( sqlite3CodeRowTrigger(pParse, TK_UPDATE, pChanges, TRIGGER_AFTER, pTab, 
          newIdx, oldIdx, onError, addr, &old_col_mask, &new_col_mask) ){
      goto update_cleanup;
    }
    iEndAfterTrigger = sqlite3VdbeAddOp2(v, OP_Goto, 0, 0);
    sqlite3VdbeJumpHere(v, iGoto);
  }

  /* If we are trying to update a view, realize that view into
  ** a ephemeral table.
  */
#if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
  if( isView ){
    sqlite3MaterializeView(pParse, pTab, pWhere, iCur);
  }
#endif

  /* Resolve the column names in all the expressions in the
  ** WHERE clause.
  */
  if( sqlite3ResolveExprNames(&sNC, pWhere) ){
    goto update_cleanup;
  }

  /* Begin the database scan
  */
  sqlite3VdbeAddOp2(v, OP_Null, 0, regOldRowid);
  pWInfo = sqlite3WhereBegin(pParse, pTabList, pWhere, 0,
                             WHERE_ONEPASS_DESIRED, 0);
  if( pWInfo==0 ) goto update_cleanup;
  okOnePass = pWInfo->okOnePass;

  /* Remember the rowid of every item to be updated.
  */
  sqlite3VdbeAddOp2(v, IsVirtual(pTab)?OP_VRowid:OP_Rowid, iCur, regOldRowid);
  if( !okOnePass ){
    regRowSet = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_RowSetAdd, regRowSet, regOldRowid);
  }

  /* End the database scan loop.
  */
  sqlite3WhereEnd(pWInfo);

  /* Initialize the count of updated rows
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack ){
    regRowCount = ++pParse->nMem;
    sqlite3VdbeAddOp2(v, OP_Integer, 0, regRowCount);
  }

  if( !isView && !IsVirtual(pTab) ){
    /* 
    ** 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.
    */
    if( !okOnePass ) sqlite3OpenTable(pParse, iCur, iDb, pTab, OP_OpenWrite); 
    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 || aRegIdx[i]>0 ){
        KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIdx);
        sqlite3VdbeAddOp4(v, OP_OpenWrite, iCur+i+1, pIdx->tnum, iDb,
                       (char*)pKey, P4_KEYINFO_HANDOFF);
        assert( pParse->nTab>iCur+i+1 );
      }
    }
  }
  
  /* Jump back to this point if a trigger encounters an IGNORE constraint. */
  if( triggers_exist ){
    sqlite3VdbeResolveLabel(v, addr);
  }

  /* Top of the update loop */
  if( okOnePass ){
    int a1 = sqlite3VdbeAddOp1(v, OP_NotNull, regOldRowid);
    addr = sqlite3VdbeAddOp0(v, OP_Goto);
    sqlite3VdbeJumpHere(v, a1);
  }else{
    addr = sqlite3VdbeAddOp3(v, OP_RowSetRead, regRowSet, 0, regOldRowid);
  }

  if( triggers_exist ){
    int regRowid;
    int regRow;
    int regCols;

    /* Make cursor iCur point to the record that is being updated.
    */
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);

    /* Generate the OLD table
    */
    regRowid = sqlite3GetTempReg(pParse);
    regRow = sqlite3GetTempReg(pParse);
    sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
    if( !old_col_mask ){
      sqlite3VdbeAddOp2(v, OP_Null, 0, regRow);
    }else{
      sqlite3VdbeAddOp2(v, OP_RowData, iCur, regRow);
    }
    sqlite3VdbeAddOp3(v, OP_Insert, oldIdx, regRow, regRowid);

    /* Generate the NEW table
    */
    if( chngRowid ){
      sqlite3ExprCodeAndCache(pParse, pRowidExpr, regRowid);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, regRowid);
    }else{
      sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regRowid);
    }
    regCols = sqlite3GetTempRange(pParse, pTab->nCol);
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
        continue;
      }
      j = aXRef[i];
      if( new_col_mask&((u32)1<<i) || new_col_mask==0xffffffff ){
        if( j<0 ){
          sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regCols+i);
          sqlite3ColumnDefault(v, pTab, i);
        }else{
          sqlite3ExprCodeAndCache(pParse, pChanges->a[j].pExpr, regCols+i);
        }
      }else{
        sqlite3VdbeAddOp2(v, OP_Null, 0, regCols+i);
      }
    }
    sqlite3VdbeAddOp3(v, OP_MakeRecord, regCols, pTab->nCol, regRow);
    if( !isView ){
      sqlite3TableAffinityStr(v, pTab);
      sqlite3ExprCacheAffinityChange(pParse, regCols, pTab->nCol);
    }
    sqlite3ReleaseTempRange(pParse, regCols, pTab->nCol);
    /* if( pParse->nErr ) goto update_cleanup; */
    sqlite3VdbeAddOp3(v, OP_Insert, newIdx, regRow, regRowid);
    sqlite3ReleaseTempReg(pParse, regRowid);
    sqlite3ReleaseTempReg(pParse, regRow);

    sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginBeforeTrigger);
    sqlite3VdbeJumpHere(v, iEndBeforeTrigger);
  }

  if( !isView && !IsVirtual(pTab) ){
    /* 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 entries.
    ** So make the cursor point at the old record.
    */
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addr, regOldRowid);

    /* 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( chngRowid ){
      sqlite3ExprCode(pParse, pRowidExpr, regNewRowid);
      sqlite3VdbeAddOp1(v, OP_MustBeInt, regNewRowid);
    }

    /* Compute new data for this record.  
    */
    for(i=0; i<pTab->nCol; i++){
      if( i==pTab->iPKey ){
        sqlite3VdbeAddOp2(v, OP_Null, 0, regData+i);
        continue;
      }
      j = aXRef[i];
      if( j<0 ){
        sqlite3VdbeAddOp3(v, OP_Column, iCur, i, regData+i);
        sqlite3ColumnDefault(v, pTab, i);
      }else{
        sqlite3ExprCode(pParse, pChanges->a[j].pExpr, regData+i);
      }
    }

    /* Do constraint checks
    */
    sqlite3GenerateConstraintChecks(pParse, pTab, iCur, regNewRowid,
                                    aRegIdx, chngRowid, 1,
                                    onError, addr);

    /* Delete the old indices for the current record.
    */
    j1 = sqlite3VdbeAddOp3(v, OP_NotExists, iCur, 0, regOldRowid);
    sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, aRegIdx);

    /* If changing the record number, delete the old record.
    */
    if( chngRowid ){
      sqlite3VdbeAddOp2(v, OP_Delete, iCur, 0);
    }
    sqlite3VdbeJumpHere(v, j1);

    /* Create the new index entries and the new record.
    */
    sqlite3CompleteInsertion(pParse, pTab, iCur, regNewRowid, 
                             aRegIdx, 1, -1, 0);
  }

  /* Increment the row counter 
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack){
    sqlite3VdbeAddOp2(v, OP_AddImm, regRowCount, 1);
  }

  /* If there are triggers, close all the cursors after each iteration
  ** through the loop.  The fire the after triggers.
  */
  if( triggers_exist ){
    sqlite3VdbeAddOp2(v, OP_Goto, 0, iBeginAfterTrigger);
    sqlite3VdbeJumpHere(v, iEndAfterTrigger);
  }

  /* Repeat the above with the next record to be updated, until
  ** all record selected by the WHERE clause have been updated.
  */
  sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
  sqlite3VdbeJumpHere(v, addr);

  /* Close all tables */
  for(i=0, pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext, i++){
    if( openAll || aRegIdx[i]>0 ){
      sqlite3VdbeAddOp2(v, OP_Close, iCur+i+1, 0);
    }
  }
  sqlite3VdbeAddOp2(v, OP_Close, iCur, 0);
  if( triggers_exist ){
    sqlite3VdbeAddOp2(v, OP_Close, newIdx, 0);
    sqlite3VdbeAddOp2(v, OP_Close, oldIdx, 0);
  }

  /*
  ** Return the number of rows that were changed. If this routine is 
  ** generating code because of a call to sqlite3NestedParse(), do not
  ** invoke the callback function.
  */
  if( db->flags & SQLITE_CountRows && !pParse->trigStack && pParse->nested==0 ){
    sqlite3VdbeAddOp2(v, OP_ResultRow, regRowCount, 1);
    sqlite3VdbeSetNumCols(v, 1);
    sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows updated", SQLITE_STATIC);
  }

update_cleanup:
  sqlite3AuthContextPop(&sContext);
  sqlite3DbFree(db, aRegIdx);
  sqlite3DbFree(db, aXRef);
  sqlite3SrcListDelete(db, pTabList);
  sqlite3ExprListDelete(db, pChanges);
  sqlite3ExprDelete(db, pWhere);
  return;
}