text: /*
  ** 2001 September 15
  **
  ** The author disclaims copyright to this source code.  In place of
  ** a legal notice, here is a blessing:
  **
  **    May you do good and not evil.
  **    May you find forgiveness for yourself and forgive others.
  **    May you share freely, never taking more than you give.
  **
  *************************************************************************
  ** This file contains C code routines that are called by the parser
  ** in order to generate code for DELETE FROM statements.
  */
  #include "sqliteInt.h"
  
  /*
  ** While a SrcList can in general represent multiple tables and subqueries
  ** (as in the FROM clause of a SELECT statement) in this case it contains
  ** the name of a single table, as one might find in an INSERT, DELETE,
  ** or UPDATE statement.  Look up that table in the symbol table and
  ** return a pointer.  Set an error message and return NULL if the table 
  ** name is not found or if any other error occurs.
  **
  ** The following fields are initialized appropriate in pSrc:
  **
  **    pSrc->a[0].pTab       Pointer to the Table object
  **    pSrc->a[0].pIndex     Pointer to the INDEXED BY index, if there is one
  **
  */
  Table *sqlite3SrcListLookup(Parse *pParse, SrcList *pSrc){
    struct SrcList_item *pItem = pSrc->a;
    Table *pTab;
    assert( pItem && pSrc->nSrc==1 );
    pTab = sqlite3LocateTable(pParse, 0, pItem->zName, pItem->zDatabase);
    sqlite3DeleteTable(pParse->db, pItem->pTab);
    pItem->pTab = pTab;
    if( pTab ){
      pTab->nRef++;
    }
    if( sqlite3IndexedByLookup(pParse, pItem) ){
      pTab = 0;
    }
    return pTab;
  }
  
  /*
  ** Check to make sure the given table is writable.  If it is not
  ** writable, generate an error message and return 1.  If it is
  ** writable return 0;
  */
  int sqlite3IsReadOnly(Parse *pParse, Table *pTab, int viewOk){
    /* A table is not writable under the following circumstances:
    **
    **   1) It is a virtual table and no implementation of the xUpdate method
    **      has been provided, or
    **   2) It is a system table (i.e. sqlite_master), this call is not
    **      part of a nested parse and writable_schema pragma has not 
    **      been specified.
    **
    ** In either case leave an error message in pParse and return non-zero.
    */
    if( ( IsVirtual(pTab) 
       && sqlite3GetVTable(pParse->db, pTab)->pMod->pModule->xUpdate==0 )
     || ( (pTab->tabFlags & TF_Readonly)!=0
       && (pParse->db->flags & SQLITE_WriteSchema)==0
       && pParse->nested==0 )
    ){
      sqlite3ErrorMsg(pParse, "table %s may not be modified", pTab->zName);
      return 1;
    }
  
  #ifndef SQLITE_OMIT_VIEW
    if( !viewOk && pTab->pSelect ){
      sqlite3ErrorMsg(pParse,"cannot modify %s because it is a view",pTab->zName);
      return 1;
    }
  #endif
    return 0;
  }
  
  
  #if !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER)
  /*
  ** Evaluate a view and store its result in an ephemeral table.  The
  ** pWhere argument is an optional WHERE clause that restricts the
  ** set of rows in the view that are to be added to the ephemeral table.
  */
  void sqlite3MaterializeView(
    Parse *pParse,       /* Parsing context */
    Table *pView,        /* View definition */
    Expr *pWhere,        /* Optional WHERE clause to be added */
    int iCur             /* Cursor number for ephemerial table */
  ){
    SelectDest dest;
    Select *pDup;
    sqlite3 *db = pParse->db;
  
    pDup = sqlite3SelectDup(db, pView->pSelect, 0);
    if( pWhere ){
      SrcList *pFrom;
      
      pWhere = sqlite3ExprDup(db, pWhere, 0);
      pFrom = sqlite3SrcListAppend(db, 0, 0, 0);
      if( pFrom ){
        assert( pFrom->nSrc==1 );
        pFrom->a[0].zAlias = sqlite3DbStrDup(db, pView->zName);
        pFrom->a[0].pSelect = pDup;
        assert( pFrom->a[0].pOn==0 );
        assert( pFrom->a[0].pUsing==0 );
      }else{
        sqlite3SelectDelete(db, pDup);
      }
      pDup = sqlite3SelectNew(pParse, 0, pFrom, pWhere, 0, 0, 0, 0, 0, 0);
    }
    sqlite3SelectDestInit(&dest, SRT_EphemTab, iCur);
    sqlite3Select(pParse, pDup, &dest);
    sqlite3SelectDelete(db, pDup);
  }
  #endif /* !defined(SQLITE_OMIT_VIEW) && !defined(SQLITE_OMIT_TRIGGER) */
  
  #if defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY)
  /*
  ** Generate an expression tree to implement the WHERE, ORDER BY,
  ** and LIMIT/OFFSET portion of DELETE and UPDATE statements.
  **
  **     DELETE FROM table_wxyz WHERE a<5 ORDER BY a LIMIT 1;
  **                            \__________________________/
  **                               pLimitWhere (pInClause)
  */
  Expr *sqlite3LimitWhere(
    Parse *pParse,               /* The parser context */
    SrcList *pSrc,               /* the FROM clause -- which tables to scan */
    Expr *pWhere,                /* The WHERE clause.  May be null */
    ExprList *pOrderBy,          /* The ORDER BY clause.  May be null */
    Expr *pLimit,                /* The LIMIT clause.  May be null */
    Expr *pOffset,               /* The OFFSET clause.  May be null */
    char *zStmtType              /* Either DELETE or UPDATE.  For error messages. */
  ){
    Expr *pWhereRowid = NULL;    /* WHERE rowid .. */
    Expr *pInClause = NULL;      /* WHERE rowid IN ( select ) */
    Expr *pSelectRowid = NULL;   /* SELECT rowid ... */
    ExprList *pEList = NULL;     /* Expression list contaning only pSelectRowid */
    SrcList *pSelectSrc = NULL;  /* SELECT rowid FROM x ... (dup of pSrc) */
    Select *pSelect = NULL;      /* Complete SELECT tree */
  
    /* Check that there isn't an ORDER BY without a LIMIT clause.
    */
    if( pOrderBy && (pLimit == 0) ) {
      sqlite3ErrorMsg(pParse, "ORDER BY without LIMIT on %s", zStmtType);
      goto limit_where_cleanup_2;
    }
  
    /* We only need to generate a select expression if there
    ** is a limit/offset term to enforce.
    */
    if( pLimit == 0 ) {
      /* if pLimit is null, pOffset will always be null as well. */
      assert( pOffset == 0 );
      return pWhere;
    }
  
    /* Generate a select expression tree to enforce the limit/offset 
    ** term for the DELETE or UPDATE statement.  For example:
    **   DELETE FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
    ** becomes:
    **   DELETE FROM table_a WHERE rowid IN ( 
    **     SELECT rowid FROM table_a WHERE col1=1 ORDER BY col2 LIMIT 1 OFFSET 1
    **   );
    */
  
    pSelectRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
    if( pSelectRowid == 0 ) goto limit_where_cleanup_2;
    pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);
    if( pEList == 0 ) goto limit_where_cleanup_2;
  
    /* duplicate the FROM clause as it is needed by both the DELETE/UPDATE tree
    ** and the SELECT subtree. */
    pSelectSrc = sqlite3SrcListDup(pParse->db, pSrc, 0);
    if( pSelectSrc == 0 ) {
      sqlite3ExprListDelete(pParse->db, pEList);
      goto limit_where_cleanup_2;
    }
  
    /* generate the SELECT expression tree. */
    pSelect = sqlite3SelectNew(pParse,pEList,pSelectSrc,pWhere,0,0,
                               pOrderBy,0,pLimit,pOffset);
    if( pSelect == 0 ) return 0;
  
    /* now generate the new WHERE rowid IN clause for the DELETE/UDPATE */
    pWhereRowid = sqlite3PExpr(pParse, TK_ROW, 0, 0, 0);
    if( pWhereRowid == 0 ) goto limit_where_cleanup_1;
    pInClause = sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0);
    if( pInClause == 0 ) goto limit_where_cleanup_1;
  
    pInClause->x.pSelect = pSelect;
    pInClause->flags |= EP_xIsSelect;
    sqlite3ExprSetHeight(pParse, pInClause);
    return pInClause;
  
    /* something went wrong. clean up anything allocated. */
  limit_where_cleanup_1:
    sqlite3SelectDelete(pParse->db, pSelect);
    return 0;
  
  limit_where_cleanup_2:
    sqlite3ExprDelete(pParse->db, pWhere);
    sqlite3ExprListDelete(pParse->db, pOrderBy);
    sqlite3ExprDelete(pParse->db, pLimit);
    sqlite3ExprDelete(pParse->db, pOffset);
    return 0;
  }
  #endif /* defined(SQLITE_ENABLE_UPDATE_DELETE_LIMIT) && !defined(SQLITE_OMIT_SUBQUERY) */
  
  /*
  ** Generate code for a DELETE FROM statement.
  **
  **     DELETE FROM table_wxyz WHERE a<5 AND b NOT NULL;
  **                 \________/       \________________/
  **                  pTabList              pWhere
  */
  void sqlite3DeleteFrom(
    Parse *pParse,         /* The parser context */
    SrcList *pTabList,     /* The table from which we should delete things */
    Expr *pWhere           /* The WHERE clause.  May be null */
  ){
    Vdbe *v;               /* The virtual database engine */
    Table *pTab;           /* The table from which records will be deleted */
    const char *zDb;       /* Name of database holding pTab */
    int end, addr = 0;     /* A couple addresses of generated code */
    int i;                 /* Loop counter */
    WhereInfo *pWInfo;     /* Information about the WHERE clause */
    Index *pIdx;           /* For looping over indices of the table */
    int iCur;              /* VDBE Cursor number for pTab */
    sqlite3 *db;           /* Main database structure */
    AuthContext sContext;  /* Authorization context */
    NameContext sNC;       /* Name context to resolve expressions in */
    int iDb;               /* Database number */
    int memCnt = -1;       /* Memory cell used for change counting */
    int rcauth;            /* Value returned by authorization callback */
  
  #ifndef SQLITE_OMIT_TRIGGER
    int isView;                  /* True if attempting to delete from a view */
    Trigger *pTrigger;           /* List of table triggers, if required */
  #endif
  
    memset(&sContext, 0, sizeof(sContext));
    db = pParse->db;
    if( pParse->nErr || db->mallocFailed ){
      goto delete_from_cleanup;
    }
    assert( pTabList->nSrc==1 );
  
    /* Locate the table which we want to delete.  This table has to be
    ** put in an SrcList structure because some of the subroutines we
    ** will be calling are designed to work with multiple tables and expect
    ** an SrcList* parameter instead of just a Table* parameter.
    */
    pTab = sqlite3SrcListLookup(pParse, pTabList);
    if( pTab==0 )  goto delete_from_cleanup;
  
    /* Figure out if we have any triggers and if the table being
    ** deleted from is a view
    */
  #ifndef SQLITE_OMIT_TRIGGER
    pTrigger = sqlite3TriggersExist(pParse, pTab, TK_DELETE, 0, 0);
    isView = pTab->pSelect!=0;
  #else
  # define pTrigger 0
  # define isView 0
  #endif
  #ifdef SQLITE_OMIT_VIEW
  # undef isView
  # define isView 0
  #endif
  
    /* If pTab is really a view, make sure it has been initialized.
    */
    if( sqlite3ViewGetColumnNames(pParse, pTab) ){
      goto delete_from_cleanup;
    }
  
    if( sqlite3IsReadOnly(pParse, pTab, (pTrigger?1:0)) ){
      goto delete_from_cleanup;
    }
    iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
    assert( iDb<db->nDb );
    zDb = db->aDb[iDb].zName;
    rcauth = sqlite3AuthCheck(pParse, SQLITE_DELETE, pTab->zName, 0, zDb);
    assert( rcauth==SQLITE_OK || rcauth==SQLITE_DENY || rcauth==SQLITE_IGNORE );
    if( rcauth==SQLITE_DENY ){
      goto delete_from_cleanup;
    }
    assert(!isView || pTrigger);
  
    /* Assign  cursor number to the table and all its indices.
    */
    assert( pTabList->nSrc==1 );
    iCur = pTabList->a[0].iCursor = pParse->nTab++;
    for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
      pParse->nTab++;
    }
  
    /* Start the view context
    */
    if( isView ){
      sqlite3AuthContextPush(pParse, &sContext, pTab->zName);
    }
  
    /* Begin generating code.
    */
    v = sqlite3GetVdbe(pParse);
    if( v==0 ){
      goto delete_from_cleanup;
    }
    if( pParse->nested==0 ) sqlite3VdbeCountChanges(v);
    sqlite3BeginWriteOperation(pParse, 1, iDb);
  
    /* If we are trying to delete from 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 the WHERE clause.
    */
    memset(&sNC, 0, sizeof(sNC));
    sNC.pParse = pParse;
    sNC.pSrcList = pTabList;
    if( sqlite3ResolveExprNames(&sNC, pWhere) ){
      goto delete_from_cleanup;
    }
  
    /* Initialize the counter of the number of rows deleted, if
    ** we are counting rows.
    */
    if( db->flags & SQLITE_CountRows ){
      memCnt = ++pParse->nMem;
      sqlite3VdbeAddOp2(v, OP_Integer, 0, memCnt);
    }
  
  #ifndef SQLITE_OMIT_TRUNCATE_OPTIMIZATION
    /* Special case: A DELETE without a WHERE clause deletes everything.
    ** It is easier just to erase the whole table. Prior to version 3.6.5,
    ** this optimization caused the row change count (the value returned by 
    ** API function sqlite3_count_changes) to be set incorrectly.  */
    if( rcauth==SQLITE_OK && pWhere==0 && !pTrigger && !IsVirtual(pTab) 
     && 0==sqlite3FkRequired(pParse, pTab, 0, 0)
    ){
      assert( !isView );
      sqlite3VdbeAddOp4(v, OP_Clear, pTab->tnum, iDb, memCnt,
                        pTab->zName, P4_STATIC);
      for(pIdx=pTab->pIndex; pIdx; pIdx=pIdx->pNext){
        assert( pIdx->pSchema==pTab->pSchema );
        sqlite3VdbeAddOp2(v, OP_Clear, pIdx->tnum, iDb);
      }
    }else
  #endif /* SQLITE_OMIT_TRUNCATE_OPTIMIZATION */
    /* The usual case: There is a WHERE clause so we have to scan through
    ** the table and pick which records to delete.
    */
    {
      int iRowSet = ++pParse->nMem;   /* Register for rowset of rows to delete */
      int iRowid = ++pParse->nMem;    /* Used for storing rowid values. */
      int regRowid;                   /* Actual register containing rowids */
  
      /* Collect rowids of every row to be deleted.
      */
      sqlite3VdbeAddOp2(v, OP_Null, 0, iRowSet);
      pWInfo = sqlite3WhereBegin(
          pParse, pTabList, pWhere, 0, 0, WHERE_DUPLICATES_OK, 0
      );
      if( pWInfo==0 ) goto delete_from_cleanup;
      regRowid = sqlite3ExprCodeGetColumn(pParse, pTab, -1, iCur, iRowid, 0);
      sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, regRowid);
      if( db->flags & SQLITE_CountRows ){
        sqlite3VdbeAddOp2(v, OP_AddImm, memCnt, 1);
      }
      sqlite3WhereEnd(pWInfo);
  
      /* Delete every item whose key was written to the list during the
      ** database scan.  We have to delete items after the scan is complete
      ** because deleting an item can change the scan order.  */
      end = sqlite3VdbeMakeLabel(v);
  
      /* Unless this is a view, open cursors for the table we are 
      ** deleting from and all its indices. If this is a view, then the
      ** only effect this statement has is to fire the INSTEAD OF 
      ** triggers.  */
      if( !isView ){
        sqlite3OpenTableAndIndices(pParse, pTab, iCur, OP_OpenWrite);
      }
  
      addr = sqlite3VdbeAddOp3(v, OP_RowSetRead, iRowSet, end, iRowid);
  
      /* Delete the row */
  #ifndef SQLITE_OMIT_VIRTUALTABLE
      if( IsVirtual(pTab) ){
        const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
        sqlite3VtabMakeWritable(pParse, pTab);
        sqlite3VdbeAddOp4(v, OP_VUpdate, 0, 1, iRowid, pVTab, P4_VTAB);
        sqlite3VdbeChangeP5(v, OE_Abort);
        sqlite3MayAbort(pParse);
      }else
  #endif
      {
        int count = (pParse->nested==0);    /* True to count changes */
        sqlite3GenerateRowDelete(pParse, pTab, iCur, iRowid, count, pTrigger, OE_Default);
      }
  
      /* End of the delete loop */
      sqlite3VdbeAddOp2(v, OP_Goto, 0, addr);
      sqlite3VdbeResolveLabel(v, end);
  
      /* Close the cursors open on the table and its indexes. */
      if( !isView && !IsVirtual(pTab) ){
        for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
          sqlite3VdbeAddOp2(v, OP_Close, iCur + i, pIdx->tnum);
        }
        sqlite3VdbeAddOp1(v, OP_Close, iCur);
      }
    }
  
    /* Update the sqlite_sequence table by storing the content of the
    ** maximum rowid counter values recorded while inserting into
    ** autoincrement tables.
    */
    if( pParse->nested==0 && pParse->pTriggerTab==0 ){
      sqlite3AutoincrementEnd(pParse);
    }
  
    /* Return the number of rows that were deleted. 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 && !pParse->pTriggerTab ){
      sqlite3VdbeAddOp2(v, OP_ResultRow, memCnt, 1);
      sqlite3VdbeSetNumCols(v, 1);
      sqlite3VdbeSetColName(v, 0, COLNAME_NAME, "rows deleted", SQLITE_STATIC);
    }
  
  delete_from_cleanup:
    sqlite3AuthContextPop(&sContext);
    sqlite3SrcListDelete(db, pTabList);
    sqlite3ExprDelete(db, pWhere);
    return;
  }
  /* Make sure "isView" and other macros defined above are undefined. Otherwise
  ** thely may interfere with compilation of other functions in this file
  ** (or in another file, if this file becomes part of the amalgamation).  */
  #ifdef isView
   #undef isView
  #endif
  #ifdef pTrigger
   #undef pTrigger
  #endif
  
  /*
  ** This routine generates VDBE code that causes a single row of a
  ** single table to be deleted.
  **
  ** The VDBE must be in a particular state when this routine is called.
  ** These are the requirements:
  **
  **   1.  A read/write cursor pointing to pTab, the table containing the row
  **       to be deleted, must be opened as cursor number $iCur.
  **
  **   2.  Read/write cursors for all indices of pTab must be open as
  **       cursor number base+i for the i-th index.
  **
  **   3.  The record number of the row to be deleted must be stored in
  **       memory cell iRowid.
  **
  ** This routine generates code to remove both the table record and all 
  ** index entries that point to that record.
  */
  void sqlite3GenerateRowDelete(
    Parse *pParse,     /* Parsing context */
    Table *pTab,       /* Table containing the row to be deleted */
    int iCur,          /* Cursor number for the table */
    int iRowid,        /* Memory cell that contains the rowid to delete */
    int count,         /* If non-zero, increment the row change counter */
    Trigger *pTrigger, /* List of triggers to (potentially) fire */
    int onconf         /* Default ON CONFLICT policy for triggers */
  ){
    Vdbe *v = pParse->pVdbe;        /* Vdbe */
    int iOld = 0;                   /* First register in OLD.* array */
    int iLabel;                     /* Label resolved to end of generated code */
  
    /* Vdbe is guaranteed to have been allocated by this stage. */
    assert( v );
  
    /* Seek cursor iCur to the row to delete. If this row no longer exists 
    ** (this can happen if a trigger program has already deleted it), do
    ** not attempt to delete it or fire any DELETE triggers.  */
    iLabel = sqlite3VdbeMakeLabel(v);
    sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
   
    /* If there are any triggers to fire, allocate a range of registers to
    ** use for the old.* references in the triggers.  */
    if( sqlite3FkRequired(pParse, pTab, 0, 0) || pTrigger ){
      u32 mask;                     /* Mask of OLD.* columns in use */
      int iCol;                     /* Iterator used while populating OLD.* */
  
      /* TODO: Could use temporary registers here. Also could attempt to
      ** avoid copying the contents of the rowid register.  */
      mask = sqlite3TriggerColmask(
          pParse, pTrigger, 0, 0, TRIGGER_BEFORE|TRIGGER_AFTER, pTab, onconf
      );
      mask |= sqlite3FkOldmask(pParse, pTab);
      iOld = pParse->nMem+1;
      pParse->nMem += (1 + pTab->nCol);
  
      /* Populate the OLD.* pseudo-table register array. These values will be 
      ** used by any BEFORE and AFTER triggers that exist.  */
      sqlite3VdbeAddOp2(v, OP_Copy, iRowid, iOld);
      for(iCol=0; iCol<pTab->nCol; iCol++){
        if( mask==0xffffffff || mask&(1<<iCol) ){
          sqlite3ExprCodeGetColumnOfTable(v, pTab, iCur, iCol, iOld+iCol+1);
        }
      }
  
      /* Invoke BEFORE DELETE trigger programs. */
      sqlite3CodeRowTrigger(pParse, pTrigger, 
          TK_DELETE, 0, TRIGGER_BEFORE, pTab, iOld, onconf, iLabel
      );
  
      /* Seek the cursor to the row to be deleted again. It may be that
      ** the BEFORE triggers coded above have already removed the row
      ** being deleted. Do not attempt to delete the row a second time, and 
      ** do not fire AFTER triggers.  */
      sqlite3VdbeAddOp3(v, OP_NotExists, iCur, iLabel, iRowid);
  
      /* Do FK processing. This call checks that any FK constraints that
      ** refer to this table (i.e. constraints attached to other tables) 
      ** are not violated by deleting this row.  */
      sqlite3FkCheck(pParse, pTab, iOld, 0);
    }
  
    /* Delete the index and table entries. Skip this step if pTab is really
    ** a view (in which case the only effect of the DELETE statement is to
    ** fire the INSTEAD OF triggers).  */ 
    if( pTab->pSelect==0 ){
      sqlite3GenerateRowIndexDelete(pParse, pTab, iCur, 0);
      sqlite3VdbeAddOp2(v, OP_Delete, iCur, (count?OPFLAG_NCHANGE:0));
      if( count ){
        sqlite3VdbeChangeP4(v, -1, pTab->zName, P4_TRANSIENT);
      }
    }
  
    /* Do any ON CASCADE, SET NULL or SET DEFAULT operations required to
    ** handle rows (possibly in other tables) that refer via a foreign key
    ** to the row just deleted. */ 
    sqlite3FkActions(pParse, pTab, 0, iOld);
  
    /* Invoke AFTER DELETE trigger programs. */
    sqlite3CodeRowTrigger(pParse, pTrigger, 
        TK_DELETE, 0, TRIGGER_AFTER, pTab, iOld, onconf, iLabel
    );
  
    /* Jump here if the row had already been deleted before any BEFORE
    ** trigger programs were invoked. Or if a trigger program throws a 
    ** RAISE(IGNORE) exception.  */
    sqlite3VdbeResolveLabel(v, iLabel);
  }
  
  /*
  ** This routine generates VDBE code that causes the deletion of all
  ** index entries associated with a single row of a single table.
  **
  ** The VDBE must be in a particular state when this routine is called.
  ** These are the requirements:
  **
  **   1.  A read/write cursor pointing to pTab, the table containing the row
  **       to be deleted, must be opened as cursor number "iCur".
  **
  **   2.  Read/write cursors for all indices of pTab must be open as
  **       cursor number iCur+i for the i-th index.
  **
  **   3.  The "iCur" cursor must be pointing to the row that is to be
  **       deleted.
  */
  void sqlite3GenerateRowIndexDelete(
    Parse *pParse,     /* Parsing and code generating context */
    Table *pTab,       /* Table containing the row to be deleted */
    int iCur,          /* Cursor number for the table */
    int *aRegIdx       /* Only delete if aRegIdx!=0 && aRegIdx[i]>0 */
  ){
    int i;
    Index *pIdx;
    int r1;
  
    for(i=1, pIdx=pTab->pIndex; pIdx; i++, pIdx=pIdx->pNext){
      if( aRegIdx!=0 && aRegIdx[i-1]==0 ) continue;
      r1 = sqlite3GenerateIndexKey(pParse, pIdx, iCur, 0, 0);
      sqlite3VdbeAddOp3(pParse->pVdbe, OP_IdxDelete, iCur+i, r1,pIdx->nColumn+1);
    }
  }
  
  /*
  ** Generate code that will assemble an index key and put it in register
  ** regOut.  The key with be for index pIdx which is an index on pTab.
  ** iCur is the index of a cursor open on the pTab table and pointing to
  ** the entry that needs indexing.
  **
  ** Return a register number which is the first in a block of
  ** registers that holds the elements of the index key.  The
  ** block of registers has already been deallocated by the time
  ** this routine returns.
  */
  int sqlite3GenerateIndexKey(
    Parse *pParse,     /* Parsing context */
    Index *pIdx,       /* The index for which to generate a key */
    int iCur,          /* Cursor number for the pIdx->pTable table */
    int regOut,        /* Write the new index key to this register */
    int doMakeRec      /* Run the OP_MakeRecord instruction if true */
  ){
    Vdbe *v = pParse->pVdbe;
    int j;
    Table *pTab = pIdx->pTable;
    int regBase;
    int nCol;
  
    nCol = pIdx->nColumn;
    regBase = sqlite3GetTempRange(pParse, nCol+1);
    sqlite3VdbeAddOp2(v, OP_Rowid, iCur, regBase+nCol);
    for(j=0; j<nCol; j++){
      int idx = pIdx->aiColumn[j];
      if( idx==pTab->iPKey ){
        sqlite3VdbeAddOp2(v, OP_SCopy, regBase+nCol, regBase+j);
      }else{
        sqlite3VdbeAddOp3(v, OP_Column, iCur, idx, regBase+j);
        sqlite3ColumnDefault(v, pTab, idx, -1);
      }
    }
    if( doMakeRec ){
      const char *zAff;
      if( pTab->pSelect || (pParse->db->flags & SQLITE_IdxRealAsInt)!=0 ){
        zAff = 0;
      }else{
        zAff = sqlite3IndexAffinityStr(v, pIdx);
      }
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regBase, nCol+1, regOut);
      sqlite3VdbeChangeP4(v, -1, zAff, P4_TRANSIENT);
    }
    sqlite3ReleaseTempRange(pParse, regBase, nCol+1);
    return regBase;
  }
  