SQLite

** as having been used.
**
** The zWhere string must have been obtained from sqlite3_malloc().
** This routine will take ownership of the allocated memory.
*/
void sqlite3VdbeAddParseSchemaOp(Vdbe *p, int iDb, char *zWhere){
  int j;
  int addr = sqlite3VdbeAddOp3(p, OP_ParseSchema, iDb, 0, 0);
  sqlite3VdbeChangeP4(p, addr, zWhere, P4_DYNAMIC);
  for(j=0; j<p->db->nDb; j++) sqlite3VdbeUsesBtree(p, j);
}

/*
** Add an opcode that includes the p4 value as an integer.
*/
int sqlite3VdbeAddOp4Int(

** opcodes contained within. If aOp is not NULL it is assumed to contain 
** nOp entries. 
*/
static void vdbeFreeOpArray(sqlite3 *db, Op *aOp, int nOp){
  if( aOp ){
    Op *pOp;
    for(pOp=aOp; pOp<&aOp[nOp]; pOp++){
      freeP4(db, pOp->p4type, pOp->p4.p);
#ifdef SQLITE_ENABLE_EXPLAIN_COMMENTS
      sqlite3DbFree(db, pOp->zComment);
#endif     
    }
  }
  sqlite3DbFree(db, aOp);
}

** 
** Other values of n (P4_STATIC, P4_COLLSEQ etc.) indicate that zP4 points
** to a string or structure that is guaranteed to exist for the lifetime of
** the Vdbe. In these cases we can just copy the pointer.
**
** If addr<0 then change P4 on the most recently inserted instruction.
*/



















void sqlite3VdbeChangeP4(Vdbe *p, int addr, const char *zP4, int n){
  Op *pOp;
  sqlite3 *db;
  assert( p!=0 );
  db = p->db;
  assert( p->magic==VDBE_MAGIC_INIT );
  if( p->aOp==0 || db->mallocFailed ){
    if( n!=P4_VTAB ){
      freeP4(db, n, (void*)*(char**)&zP4);
    }
    return;
  }
  assert( p->nOp>0 );
  assert( addr<p->nOp );
  if( addr<0 ){
    addr = p->nOp - 1;
  }
  pOp = &p->aOp[addr];
  assert( pOp->p4type==P4_NOTUSED
       || pOp->p4type==P4_INT32
       || pOp->p4type==P4_KEYINFO );
  freeP4(db, pOp->p4type, pOp->p4.p);
  pOp->p4.p = 0;

  if( n==P4_INT32 ){
    /* Note: this cast is safe, because the origin data point was an int
    ** that was cast to a (const char *). */
    pOp->p4.i = SQLITE_PTR_TO_INT(zP4);
    pOp->p4type = P4_INT32;
  }else if( zP4==0 ){
    pOp->p4.p = 0;
    pOp->p4type = P4_NOTUSED;
  }else if( n==P4_KEYINFO ){
    pOp->p4.p = (void*)zP4;
    pOp->p4type = P4_KEYINFO;
#ifdef SQLITE_ENABLE_CURSOR_HINTS
  }else if( n==P4_EXPR ){
    /* Responsibility for deleting the Expr tree is handed over to the
    ** VDBE by this operation.  The caller should have already invoked
    ** sqlite3ExprDup() or whatever other routine is needed to make a 
    ** private copy of the tree. */
    pOp->p4.pExpr = (Expr*)zP4;
    pOp->p4type = P4_EXPR;
#endif
  }else if( n==P4_VTAB ){
    pOp->p4.p = (void*)zP4;
    pOp->p4type = P4_VTAB;
    sqlite3VtabLock((VTable *)zP4);
    assert( ((VTable *)zP4)->db==p->db );
  }else if( n<0 ){
    pOp->p4.p = (void*)zP4;
    pOp->p4type = (signed char)n;
  }else{
    if( n==0 ) n = sqlite3Strlen30(zP4);
    pOp->p4.z = sqlite3DbStrNDup(p->db, zP4, n);
    pOp->p4type = P4_DYNAMIC;
  }
}

/*
** Set the P4 on the most recently added opcode to the KeyInfo for the
** index given.
*/

      assert( pTabItem->iCursor==pLevel->iTabCur );
      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS-1 );
      testcase( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol==BMS );
      if( pWInfo->eOnePass==ONEPASS_OFF && pTab->nCol<BMS && HasRowid(pTab) ){
        Bitmask b = pTabItem->colUsed;
        int n = 0;
        for(; b; b=b>>1, n++){}
        sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1, 
                            SQLITE_INT_TO_PTR(n), P4_INT32);
        assert( n<=pTab->nCol );
      }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
      if( pLoop->u.btree.pIndex!=0 ){
        sqlite3VdbeChangeP5(v, OPFLAG_SEEKEQ|bFordelete);
      }else
#endif