SQLite

  assert( cursorHoldsMutex(pCur) );
  assert( pRes!=0 );
  assert( *pRes==0 );
  assert( pCur->skipNext==0 || pCur->eState!=CURSOR_VALID );
  assert( (pCur->curFlags & (BTCF_AtLast|BTCF_ValidOvfl|BTCF_ValidNKey))==0 );
  assert( pCur->info.nSize==0 );
  if( pCur->eState!=CURSOR_VALID ){
    assert( pCur->eState>=CURSOR_REQUIRESEEK );
    rc = btreeRestoreCursorPosition(pCur);
    if( rc!=SQLITE_OK ){
      return rc;
    }
    if( CURSOR_INVALID==pCur->eState ){
      *pRes = 1;
      return SQLITE_OK;
    }

  assert( pExpr->op!=TK_REGISTER );
  sqlite3ExprCode(pParse, pExpr, target);
  iMem = ++pParse->nMem;
  sqlite3VdbeAddOp2(v, OP_Copy, target, iMem);
  exprToRegister(pExpr, iMem);
}

#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
/*
** Generate a human-readable explanation of an expression tree.
*/
void sqlite3ExplainExpr(Vdbe *pOut, Expr *pExpr){
  int op;                   /* The opcode being coded */
  const char *zBinOp = 0;   /* Binary operator */
  const char *zUniOp = 0;   /* Unary operator */

  if( pExpr==0 ){

    op = TK_NULL;
  }else{
    op = pExpr->op;
  }
  switch( op ){
    case TK_AGG_COLUMN: {
      sqlite3ExplainPrintf(pOut, "AGG{%d:%d}",
            pExpr->iTable, pExpr->iColumn);
      break;
    }
    case TK_COLUMN: {
      if( pExpr->iTable<0 ){
        /* This only happens when coding check constraints */
        sqlite3ExplainPrintf(pOut, "COLUMN(%d)", pExpr->iColumn);
      }else{
        sqlite3ExplainPrintf(pOut, "{%d:%d}",
                             pExpr->iTable, pExpr->iColumn);
      }
      break;
    }
    case TK_INTEGER: {
      if( pExpr->flags & EP_IntValue ){
        sqlite3ExplainPrintf(pOut, "%d", pExpr->u.iValue);
      }else{
        sqlite3ExplainPrintf(pOut, "%s", pExpr->u.zToken);
      }
      break;
    }
#ifndef SQLITE_OMIT_FLOATING_POINT
    case TK_FLOAT: {
      sqlite3ExplainPrintf(pOut,"%s", pExpr->u.zToken);
      break;
    }
#endif
    case TK_STRING: {
      sqlite3ExplainPrintf(pOut,"%Q", pExpr->u.zToken);
      break;
    }
    case TK_NULL: {
      sqlite3ExplainPrintf(pOut,"NULL");
      break;
    }
#ifndef SQLITE_OMIT_BLOB_LITERAL
    case TK_BLOB: {
      sqlite3ExplainPrintf(pOut,"%s", pExpr->u.zToken);
      break;
    }
#endif
    case TK_VARIABLE: {
      sqlite3ExplainPrintf(pOut,"VARIABLE(%s,%d)",
                           pExpr->u.zToken, pExpr->iColumn);
      break;
    }
    case TK_REGISTER: {
      sqlite3ExplainPrintf(pOut,"REGISTER(%d)", pExpr->iTable);
      break;
    }
    case TK_AS: {

      sqlite3ExplainExpr(pOut, pExpr->pLeft);




      break;
    }
#ifndef SQLITE_OMIT_CAST
    case TK_CAST: {
      /* Expressions of the form:   CAST(pLeft AS token) */
      const char *zAff = "unk";
      switch( sqlite3AffinityType(pExpr->u.zToken, 0) ){
        case SQLITE_AFF_TEXT:    zAff = "TEXT";     break;
        case SQLITE_AFF_NONE:    zAff = "NONE";     break;
        case SQLITE_AFF_NUMERIC: zAff = "NUMERIC";  break;
        case SQLITE_AFF_INTEGER: zAff = "INTEGER";  break;
        case SQLITE_AFF_REAL:    zAff = "REAL";     break;
      }
      sqlite3ExplainPrintf(pOut, "CAST-%s(", zAff);
      sqlite3ExplainExpr(pOut, pExpr->pLeft);
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
#endif /* SQLITE_OMIT_CAST */
    case TK_LT:      zBinOp = "LT";     break;
    case TK_LE:      zBinOp = "LE";     break;
    case TK_GT:      zBinOp = "GT";     break;
    case TK_GE:      zBinOp = "GE";     break;

    case TK_UPLUS:   zUniOp = "UPLUS";  break;
    case TK_BITNOT:  zUniOp = "BITNOT"; break;
    case TK_NOT:     zUniOp = "NOT";    break;
    case TK_ISNULL:  zUniOp = "ISNULL"; break;
    case TK_NOTNULL: zUniOp = "NOTNULL"; break;

    case TK_COLLATE: {

      sqlite3ExplainExpr(pOut, pExpr->pLeft);
      sqlite3ExplainPrintf(pOut,".COLLATE(%s)",pExpr->u.zToken);
      break;
    }

    case TK_AGG_FUNCTION:
    case TK_FUNCTION: {
      ExprList *pFarg;       /* List of function arguments */
      if( ExprHasProperty(pExpr, EP_TokenOnly) ){
        pFarg = 0;
      }else{
        pFarg = pExpr->x.pList;
      }
      if( op==TK_AGG_FUNCTION ){
        sqlite3ExplainPrintf(pOut, "AGG_FUNCTION%d:%s(",
                             pExpr->op2, pExpr->u.zToken);
      }else{
        sqlite3ExplainPrintf(pOut, "FUNCTION:%s(", pExpr->u.zToken);
      }
      if( pFarg ){
        sqlite3ExplainExprList(pOut, pFarg);
      }
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
#ifndef SQLITE_OMIT_SUBQUERY
    case TK_EXISTS: {
      sqlite3ExplainPrintf(pOut, "EXISTS(");
      sqlite3ExplainSelect(pOut, pExpr->x.pSelect);
      sqlite3ExplainPrintf(pOut,")");
      break;
    }
    case TK_SELECT: {
      sqlite3ExplainPrintf(pOut, "(");
      sqlite3ExplainSelect(pOut, pExpr->x.pSelect);
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
    case TK_IN: {
      sqlite3ExplainPrintf(pOut, "IN(");
      sqlite3ExplainExpr(pOut, pExpr->pLeft);
      sqlite3ExplainPrintf(pOut, ",");
      if( ExprHasProperty(pExpr, EP_xIsSelect) ){
        sqlite3ExplainSelect(pOut, pExpr->x.pSelect);
      }else{
        sqlite3ExplainExprList(pOut, pExpr->x.pList);
      }
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
#endif /* SQLITE_OMIT_SUBQUERY */

    /*
    **    x BETWEEN y AND z
    **
    ** This is equivalent to
    **
    **    x>=y AND x<=z
    **
    ** X is stored in pExpr->pLeft.
    ** Y is stored in pExpr->pList->a[0].pExpr.
    ** Z is stored in pExpr->pList->a[1].pExpr.
    */
    case TK_BETWEEN: {
      Expr *pX = pExpr->pLeft;
      Expr *pY = pExpr->x.pList->a[0].pExpr;
      Expr *pZ = pExpr->x.pList->a[1].pExpr;
      sqlite3ExplainPrintf(pOut, "BETWEEN(");
      sqlite3ExplainExpr(pOut, pX);
      sqlite3ExplainPrintf(pOut, ",");
      sqlite3ExplainExpr(pOut, pY);
      sqlite3ExplainPrintf(pOut, ",");
      sqlite3ExplainExpr(pOut, pZ);
      sqlite3ExplainPrintf(pOut, ")");
      break;
    }
    case TK_TRIGGER: {
      /* If the opcode is TK_TRIGGER, then the expression is a reference
      ** to a column in the new.* or old.* pseudo-tables available to
      ** trigger programs. In this case Expr.iTable is set to 1 for the
      ** new.* pseudo-table, or 0 for the old.* pseudo-table. Expr.iColumn
      ** is set to the column of the pseudo-table to read, or to -1 to
      ** read the rowid field.
      */
      sqlite3ExplainPrintf(pOut, "%s(%d)", 
          pExpr->iTable ? "NEW" : "OLD", pExpr->iColumn);
      break;
    }
    case TK_CASE: {
      sqlite3ExplainPrintf(pOut, "CASE(");
      sqlite3ExplainExpr(pOut, pExpr->pLeft);
      sqlite3ExplainPrintf(pOut, ",");
      sqlite3ExplainExprList(pOut, pExpr->x.pList);
      break;
    }
#ifndef SQLITE_OMIT_TRIGGER
    case TK_RAISE: {
      const char *zType = "unk";
      switch( pExpr->affinity ){
        case OE_Rollback:   zType = "rollback";  break;
        case OE_Abort:      zType = "abort";     break;
        case OE_Fail:       zType = "fail";      break;
        case OE_Ignore:     zType = "ignore";    break;
      }
      sqlite3ExplainPrintf(pOut, "RAISE-%s(%s)", zType, pExpr->u.zToken);
      break;
    }
#endif



  }

  if( zBinOp ){
    sqlite3ExplainPrintf(pOut,"%s(", zBinOp);
    sqlite3ExplainExpr(pOut, pExpr->pLeft);
    sqlite3ExplainPrintf(pOut,",");
    sqlite3ExplainExpr(pOut, pExpr->pRight);
    sqlite3ExplainPrintf(pOut,")");
  }else if( zUniOp ){
    sqlite3ExplainPrintf(pOut,"%s(", zUniOp);
    sqlite3ExplainExpr(pOut, pExpr->pLeft);
    sqlite3ExplainPrintf(pOut,")");
  }

}
#endif /* defined(SQLITE_ENABLE_TREE_EXPLAIN) */

#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
/*
** Generate a human-readable explanation of an expression list.
*/


void sqlite3ExplainExprList(Vdbe *pOut, ExprList *pList){



  int i;


  if( pList==0 || pList->nExpr==0 ){
    sqlite3ExplainPrintf(pOut, "(empty-list)");
    return;
  }else if( pList->nExpr==1 ){
    sqlite3ExplainExpr(pOut, pList->a[0].pExpr);
  }else{
    sqlite3ExplainPush(pOut);
    for(i=0; i<pList->nExpr; i++){
      sqlite3ExplainPrintf(pOut, "item[%d] = ", i);
      sqlite3ExplainPush(pOut);
      sqlite3ExplainExpr(pOut, pList->a[i].pExpr);
      sqlite3ExplainPop(pOut);

      if( pList->a[i].zName ){
        sqlite3ExplainPrintf(pOut, " AS %s", pList->a[i].zName);
      }
      if( pList->a[i].bSpanIsTab ){
        sqlite3ExplainPrintf(pOut, " (%s)", pList->a[i].zSpan);
      }
      if( i<pList->nExpr-1 ){
        sqlite3ExplainNL(pOut);
      }
    }
    sqlite3ExplainPop(pOut);
  }
}
#endif /* SQLITE_DEBUG */

/*
** Generate code that pushes the value of every element of the given
** expression list into a sequence of registers beginning at target.
**

    ** undo this setting.
    */
    case SQLITE_TESTCTRL_LOCALTIME_FAULT: {
      sqlite3GlobalConfig.bLocaltimeFault = va_arg(ap, int);
      break;
    }

#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
    /*   sqlite3_test_control(SQLITE_TESTCTRL_EXPLAIN_STMT,
    **                        sqlite3_stmt*,const char**);
    **
    ** If compiled with SQLITE_ENABLE_TREE_EXPLAIN, each sqlite3_stmt holds
    ** a string that describes the optimized parse tree.  This test-control
    ** returns a pointer to that string.
    */
    case SQLITE_TESTCTRL_EXPLAIN_STMT: {
      sqlite3_stmt *pStmt = va_arg(ap, sqlite3_stmt*);
      const char **pzRet = va_arg(ap, const char**);
      *pzRet = sqlite3VdbeExplanation((Vdbe*)pStmt);
      break;
    }
#endif

    /*   sqlite3_test_control(SQLITE_TESTCTRL_NEVER_CORRUPT, int);
    **
    ** Set or clear a flag that indicates that the database file is always well-
    ** formed and never corrupt.  This flag is clear by default, indicating that
    ** database files might have arbitrary corruption.  Setting the flag during
    ** testing causes certain assert() statements in the code to be activated
    ** that demonstrat invariants on well-formed database files.

%endif  SQLITE_OMIT_VIEW

//////////////////////// The SELECT statement /////////////////////////////////
//
cmd ::= select(X).  {
  SelectDest dest = {SRT_Output, 0, 0, 0, 0, 0};
  sqlite3Select(pParse, X, &dest);
  sqlite3ExplainBegin(pParse->pVdbe);
  sqlite3ExplainSelect(pParse->pVdbe, X);
  sqlite3ExplainFinish(pParse->pVdbe);
  sqlite3SelectDelete(pParse->db, X);
}

%type select {Select*}
%destructor select {sqlite3SelectDelete(pParse->db, $$);}
%type selectnowith {Select*}
%destructor selectnowith {sqlite3SelectDelete(pParse->db, $$);}

  va_end(ap);
  sqlite3StrAccumFinish(&acc);
  fprintf(stdout,"%s", zBuf);
  fflush(stdout);
}
#endif
































































/*
** variable-argument wrapper around sqlite3VXPrintf().
*/
void sqlite3XPrintf(StrAccum *p, u32 bFlags, const char *zFormat, ...){
  va_list ap;
  va_start(ap,zFormat);
  sqlite3VXPrintf(p, bFlags, zFormat, ap);

    }
  }

  /* Finially, delete what is left of the subquery and return
  ** success.
  */
  sqlite3SelectDelete(db, pSub1);








  return 1;
}
#endif /* !defined(SQLITE_OMIT_SUBQUERY) || !defined(SQLITE_OMIT_VIEW) */

/*
** Based on the contents of the AggInfo structure indicated by the first

  if( p==0 || db->mallocFailed || pParse->nErr ){
    return 1;
  }
  if( sqlite3AuthCheck(pParse, SQLITE_SELECT, 0, 0, 0) ) return 1;
  memset(&sAggInfo, 0, sizeof(sAggInfo));
#if SELECTTRACE_ENABLED
  pParse->nSelectIndent++;
  SELECTTRACE(1,pParse,p, ("begin processing\n"));



#endif

  assert( p->pOrderBy==0 || pDest->eDest!=SRT_DistFifo );
  assert( p->pOrderBy==0 || pDest->eDest!=SRT_Fifo );
  assert( p->pOrderBy==0 || pDest->eDest!=SRT_DistQueue );
  assert( p->pOrderBy==0 || pDest->eDest!=SRT_Queue );
  if( IgnorableOrderby(pDest) ){

#if SELECTTRACE_ENABLED
  SELECTTRACE(1,pParse,p,("end processing\n"));
  pParse->nSelectIndent--;
#endif
  return rc;
}

#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
/*
** Generate a human-readable description of a the Select object.
*/
static void explainOneSelect(Vdbe *pVdbe, Select *p){


  sqlite3ExplainPrintf(pVdbe, "SELECT ");
  if( p->selFlags & (SF_Distinct|SF_Aggregate) ){
    if( p->selFlags & SF_Distinct ){
      sqlite3ExplainPrintf(pVdbe, "DISTINCT ");
    }
    if( p->selFlags & SF_Aggregate ){
      sqlite3ExplainPrintf(pVdbe, "agg_flag ");
    }
    sqlite3ExplainNL(pVdbe);



    sqlite3ExplainPrintf(pVdbe, "   ");
  }
  sqlite3ExplainExprList(pVdbe, p->pEList);



  sqlite3ExplainNL(pVdbe);
  if( p->pSrc && p->pSrc->nSrc ){
    int i;
    sqlite3ExplainPrintf(pVdbe, "FROM ");
    sqlite3ExplainPush(pVdbe);
    for(i=0; i<p->pSrc->nSrc; i++){
      struct SrcList_item *pItem = &p->pSrc->a[i];



      sqlite3ExplainPrintf(pVdbe, "{%d,*} = ", pItem->iCursor);
      if( pItem->pSelect ){
        sqlite3ExplainSelect(pVdbe, pItem->pSelect);
        if( pItem->pTab ){
          sqlite3ExplainPrintf(pVdbe, " (tabname=%s)", pItem->pTab->zName);
        }
      }else if( pItem->zName ){
        sqlite3ExplainPrintf(pVdbe, "%s", pItem->zName);
      }
      if( pItem->zAlias ){
        sqlite3ExplainPrintf(pVdbe, " (AS %s)", pItem->zAlias);
      }
      if( pItem->jointype & JT_LEFT ){
        sqlite3ExplainPrintf(pVdbe, " LEFT-JOIN");
      }
      sqlite3ExplainNL(pVdbe);



    }
    sqlite3ExplainPop(pVdbe);
  }


  if( p->pWhere ){
    sqlite3ExplainPrintf(pVdbe, "WHERE ");
    sqlite3ExplainExpr(pVdbe, p->pWhere);
    sqlite3ExplainNL(pVdbe);
  }
  if( p->pGroupBy ){
    sqlite3ExplainPrintf(pVdbe, "GROUPBY ");
    sqlite3ExplainExprList(pVdbe, p->pGroupBy);
    sqlite3ExplainNL(pVdbe);
  }
  if( p->pHaving ){
    sqlite3ExplainPrintf(pVdbe, "HAVING ");
    sqlite3ExplainExpr(pVdbe, p->pHaving);
    sqlite3ExplainNL(pVdbe);
  }
  if( p->pOrderBy ){
    sqlite3ExplainPrintf(pVdbe, "ORDERBY ");
    sqlite3ExplainExprList(pVdbe, p->pOrderBy);
    sqlite3ExplainNL(pVdbe);
  }
  if( p->pLimit ){
    sqlite3ExplainPrintf(pVdbe, "LIMIT ");
    sqlite3ExplainExpr(pVdbe, p->pLimit);
    sqlite3ExplainNL(pVdbe);
  }
  if( p->pOffset ){
    sqlite3ExplainPrintf(pVdbe, "OFFSET ");
    sqlite3ExplainExpr(pVdbe, p->pOffset);
    sqlite3ExplainNL(pVdbe);
  }
}
void sqlite3ExplainSelect(Vdbe *pVdbe, Select *p){
  if( p==0 ){


    sqlite3ExplainPrintf(pVdbe, "(null-select)");
    return;

  }
  sqlite3ExplainPush(pVdbe);
  while( p ){
    explainOneSelect(pVdbe, p);
    p = p->pNext;
    if( p==0 ) break;
    sqlite3ExplainNL(pVdbe);
    sqlite3ExplainPrintf(pVdbe, "%s\n", selectOpName(p->op));
  }
  sqlite3ExplainPrintf(pVdbe, "END");
  sqlite3ExplainPop(pVdbe);
}

/* End of the structure debug printing code
*****************************************************************************/
#endif /* defined(SQLITE_ENABLE_TREE_EXPLAIN) */

            fprintf(pArg->out,"%s\n", sqlite3_column_text(pExplain, 3));
          }
        }
        sqlite3_finalize(pExplain);
        sqlite3_free(zEQP);
      }

      /* Output TESTCTRL_EXPLAIN text of requested */
      if( pArg && pArg->mode==MODE_Explain ){
        const char *zExplain = 0;
        sqlite3_test_control(SQLITE_TESTCTRL_EXPLAIN_STMT, pStmt, &zExplain);
        if( zExplain && zExplain[0] ){
          fprintf(pArg->out, "%s", zExplain);
        }
      }

      /* If the shell is currently in ".explain" mode, gather the extra
      ** data required to add indents to the output.*/
      if( pArg && pArg->mode==MODE_Explain ){
        explain_data_prepare(pArg, pStmt);
      }

      /* perform the first step.  this will tell us if we

#define SQLITE_TESTCTRL_ASSERT                  12
#define SQLITE_TESTCTRL_ALWAYS                  13
#define SQLITE_TESTCTRL_RESERVE                 14
#define SQLITE_TESTCTRL_OPTIMIZATIONS           15
#define SQLITE_TESTCTRL_ISKEYWORD               16
#define SQLITE_TESTCTRL_SCRATCHMALLOC           17
#define SQLITE_TESTCTRL_LOCALTIME_FAULT         18
#define SQLITE_TESTCTRL_EXPLAIN_STMT            19
#define SQLITE_TESTCTRL_NEVER_CORRUPT           20
#define SQLITE_TESTCTRL_VDBE_COVERAGE           21
#define SQLITE_TESTCTRL_BYTEORDER               22
#define SQLITE_TESTCTRL_ISINIT                  23
#define SQLITE_TESTCTRL_SORTER_MMAP             24
#define SQLITE_TESTCTRL_LAST                    24

/*
** Macros to compute minimum and maximum of two numbers.
*/
#define MIN(A,B) ((A)<(B)?(A):(B))
#define MAX(A,B) ((A)>(B)?(A):(B))






/*
** Check to see if this machine uses EBCDIC.  (Yes, believe it or
** not, there are still machines out there that use EBCDIC.)
*/
#if 'A' == '\301'
# define SQLITE_EBCDIC 1
#else

typedef struct SQLiteThread SQLiteThread;
typedef struct SelectDest SelectDest;
typedef struct SrcList SrcList;
typedef struct StrAccum StrAccum;
typedef struct Table Table;
typedef struct TableLock TableLock;
typedef struct Token Token;

typedef struct Trigger Trigger;
typedef struct TriggerPrg TriggerPrg;
typedef struct TriggerStep TriggerStep;
typedef struct UnpackedRecord UnpackedRecord;
typedef struct VTable VTable;
typedef struct VtabCtx VtabCtx;
typedef struct Walker Walker;

#define WHERE_ORDERBY_MIN      0x0001 /* ORDER BY processing for min() func */
#define WHERE_ORDERBY_MAX      0x0002 /* ORDER BY processing for max() func */
#define WHERE_ONEPASS_DESIRED  0x0004 /* Want to do one-pass UPDATE/DELETE */
#define WHERE_DUPLICATES_OK    0x0008 /* Ok to return a row more than once */
#define WHERE_OMIT_OPEN_CLOSE  0x0010 /* Table cursors are already open */
#define WHERE_FORCE_TABLE      0x0020 /* Do not use an index-only search */
#define WHERE_ONETABLE_ONLY    0x0040 /* Only code the 1st table in pTabList */
#define WHERE_AND_ONLY         0x0080 /* Don't use indices for OR terms */
#define WHERE_GROUPBY          0x0100 /* pOrderBy is really a GROUP BY */
#define WHERE_DISTINCTBY       0x0200 /* pOrderby is really a DISTINCT clause */
#define WHERE_WANT_DISTINCT    0x0400 /* All output needs to be distinct */
#define WHERE_SORTBYGROUP      0x0800 /* Support sqlite3WhereIsSorted() */
#define WHERE_REOPEN_IDX       0x1000 /* Try to use OP_ReopenIdx */

/* Allowed return values from sqlite3WhereIsDistinct()

    char *zName;                    /* Name of this CTE */
    ExprList *pCols;                /* List of explicit column names, or NULL */
    Select *pSelect;                /* The definition of this CTE */
    const char *zErr;               /* Error message for circular references */
  } a[1];
};












/*
** Assuming zIn points to the first byte of a UTF-8 character,
** advance zIn to point to the first byte of the next UTF-8 character.
*/
#define SQLITE_SKIP_UTF8(zIn) {                        \
  if( (*(zIn++))>=0xc0 ){                              \
    while( (*zIn & 0xc0)==0x80 ){ zIn++; }             \

#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
  void sqlite3DebugPrintf(const char*, ...);
#endif
#if defined(SQLITE_TEST)
  void *sqlite3TestTextToPtr(const char*);
#endif

/* Output formatting for SQLITE_TESTCTRL_EXPLAIN */
#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
  void sqlite3ExplainBegin(Vdbe*);
  void sqlite3ExplainPrintf(Vdbe*, const char*, ...);
  void sqlite3ExplainNL(Vdbe*);
  void sqlite3ExplainPush(Vdbe*);
  void sqlite3ExplainPop(Vdbe*);
  void sqlite3ExplainFinish(Vdbe*);
  void sqlite3ExplainSelect(Vdbe*, Select*);
  void sqlite3ExplainExpr(Vdbe*, Expr*);
  void sqlite3ExplainExprList(Vdbe*, ExprList*);
  const char *sqlite3VdbeExplanation(Vdbe*);
#else
# define sqlite3ExplainBegin(X)
# define sqlite3ExplainSelect(A,B)
# define sqlite3ExplainExpr(A,B)
# define sqlite3ExplainExprList(A,B)
# define sqlite3ExplainFinish(X)
# define sqlite3VdbeExplanation(X) 0
#endif


void sqlite3SetString(char **, sqlite3*, const char*, ...);
void sqlite3ErrorMsg(Parse*, const char*, ...);
int sqlite3Dequote(char*);
int sqlite3KeywordCode(const unsigned char*, int);

#endif
  i64 iCurrentTime;       /* Value of julianday('now') for this statement */
  i64 nFkConstraint;      /* Number of imm. FK constraints this VM */
  i64 nStmtDefCons;       /* Number of def. constraints when stmt started */
  i64 nStmtDefImmCons;    /* Number of def. imm constraints when stmt started */
  char *zSql;             /* Text of the SQL statement that generated this */
  void *pFree;            /* Free this when deleting the vdbe */
#ifdef SQLITE_ENABLE_TREE_EXPLAIN
  Explain *pExplain;      /* The explainer */
  char *zExplain;         /* Explanation of data structures */
#endif
  VdbeFrame *pFrame;      /* Parent frame */
  VdbeFrame *pDelFrame;   /* List of frame objects to free on VM reset */
  int nFrame;             /* Number of frames in pFrame list */
  u32 expmask;            /* Binding to these vars invalidates VM */
  SubProgram *pProgram;   /* Linked list of all sub-programs used by VM */
  int nOnceFlag;          /* Size of array aOnceFlag[] */
  u8 *aOnceFlag;          /* Flags for OP_Once */

    memset(pOp, 0, sizeof(pOp[0]));
    pOp->opcode = OP_Noop;
    if( addr==p->nOp-1 ) p->nOp--;
  }
}

/*
** Remove the last opcode inserted

*/
int sqlite3VdbeDeletePriorOpcode(Vdbe *p, u8 op){
  if( (p->nOp-1)>(p->pParse->iFixedOp) && p->aOp[p->nOp-1].opcode==op ){
    sqlite3VdbeChangeToNoop(p, p->nOp-1);
    return 1;
  }else{
    return 0;

    sqlite3DbFree(db, pSub);
  }
  for(i=p->nzVar-1; i>=0; i--) sqlite3DbFree(db, p->azVar[i]);
  vdbeFreeOpArray(db, p->aOp, p->nOp);
  sqlite3DbFree(db, p->aColName);
  sqlite3DbFree(db, p->zSql);
  sqlite3DbFree(db, p->pFree);
#if defined(SQLITE_ENABLE_TREE_EXPLAIN)
  sqlite3DbFree(db, p->zExplain);
  sqlite3DbFree(db, p->pExplain);
#endif
}

/*
** Delete an entire VDBE.
*/
void sqlite3VdbeDelete(Vdbe *p){
  sqlite3 *db;

      }
    }
  }
  return sqlite3StrAccumFinish(&out);
}

#endif /* #ifndef SQLITE_OMIT_TRACE */

/*****************************************************************************
** The following code implements the data-structure explaining logic
** for the Vdbe.
*/

#if defined(SQLITE_ENABLE_TREE_EXPLAIN)

/*
** Allocate a new Explain object
*/
void sqlite3ExplainBegin(Vdbe *pVdbe){
  if( pVdbe ){
    Explain *p;
    sqlite3BeginBenignMalloc();
    p = (Explain *)sqlite3MallocZero( sizeof(Explain) );
    if( p ){
      p->pVdbe = pVdbe;
      sqlite3_free(pVdbe->pExplain);
      pVdbe->pExplain = p;
      sqlite3StrAccumInit(&p->str, p->zBase, sizeof(p->zBase),
                          SQLITE_MAX_LENGTH);
      p->str.useMalloc = 2;
    }else{
      sqlite3EndBenignMalloc();
    }
  }
}

/*
** Return true if the Explain ends with a new-line.
*/
static int endsWithNL(Explain *p){
  return p && p->str.zText && p->str.nChar
           && p->str.zText[p->str.nChar-1]=='\n';
}
    
/*
** Append text to the indentation
*/
void sqlite3ExplainPrintf(Vdbe *pVdbe, const char *zFormat, ...){
  Explain *p;
  if( pVdbe && (p = pVdbe->pExplain)!=0 ){
    va_list ap;
    if( p->nIndent && endsWithNL(p) ){
      int n = p->nIndent;
      if( n>ArraySize(p->aIndent) ) n = ArraySize(p->aIndent);
      sqlite3AppendSpace(&p->str, p->aIndent[n-1]);
    }   
    va_start(ap, zFormat);
    sqlite3VXPrintf(&p->str, SQLITE_PRINTF_INTERNAL, zFormat, ap);
    va_end(ap);
  }
}

/*
** Append a '\n' if there is not already one.
*/
void sqlite3ExplainNL(Vdbe *pVdbe){
  Explain *p;
  if( pVdbe && (p = pVdbe->pExplain)!=0 && !endsWithNL(p) ){
    sqlite3StrAccumAppend(&p->str, "\n", 1);
  }
}

/*
** Push a new indentation level.  Subsequent lines will be indented
** so that they begin at the current cursor position.
*/
void sqlite3ExplainPush(Vdbe *pVdbe){
  Explain *p;
  if( pVdbe && (p = pVdbe->pExplain)!=0 ){
    if( p->str.zText && p->nIndent<ArraySize(p->aIndent) ){
      const char *z = p->str.zText;
      int i = p->str.nChar-1;
      int x;
      while( i>=0 && z[i]!='\n' ){ i--; }
      x = (p->str.nChar - 1) - i;
      if( p->nIndent && x<p->aIndent[p->nIndent-1] ){
        x = p->aIndent[p->nIndent-1];
      }
      p->aIndent[p->nIndent] = x;
    }
    p->nIndent++;
  }
}

/*
** Pop the indentation stack by one level.
*/
void sqlite3ExplainPop(Vdbe *p){
  if( p && p->pExplain ) p->pExplain->nIndent--;
}

/*
** Free the indentation structure
*/
void sqlite3ExplainFinish(Vdbe *pVdbe){
  if( pVdbe && pVdbe->pExplain ){
    sqlite3_free(pVdbe->zExplain);
    sqlite3ExplainNL(pVdbe);
    pVdbe->zExplain = sqlite3StrAccumFinish(&pVdbe->pExplain->str);
    sqlite3_free(pVdbe->pExplain);
    pVdbe->pExplain = 0;
    sqlite3EndBenignMalloc();
  }
}

/*
** Return the explanation of a virtual machine.
*/
const char *sqlite3VdbeExplanation(Vdbe *pVdbe){
  return (pVdbe && pVdbe->zExplain) ? pVdbe->zExplain : 0;
}
#endif /* defined(SQLITE_DEBUG) */

  assert( TK_GT>TK_EQ && TK_GT<TK_GE );
  assert( TK_LT>TK_EQ && TK_LT<TK_GE );
  assert( TK_LE>TK_EQ && TK_LE<TK_GE );
  assert( TK_GE==TK_EQ+4 );
  return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
}

/*
** Swap two objects of type TYPE.
*/
#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}

/*
** Commute a comparison operator.  Expressions of the form "X op Y"
** are converted into "Y op X".
**
** If left/right precedence rules come into play when determining the
** collating sequence, then COLLATE operators are adjusted to ensure
** that the collating sequence does not change.  For example:

      }
    }

    /* Run a separate WHERE clause for each term of the OR clause.  After
    ** eliminating duplicates from other WHERE clauses, the action for each
    ** sub-WHERE clause is to to invoke the main loop body as a subroutine.
    */
    wctrlFlags =  WHERE_OMIT_OPEN_CLOSE | WHERE_AND_ONLY |

                  WHERE_FORCE_TABLE | WHERE_ONETABLE_ONLY;
    for(ii=0; ii<pOrWc->nTerm; ii++){
      WhereTerm *pOrTerm = &pOrWc->a[ii];
      if( pOrTerm->leftCursor==iCur || (pOrTerm->eOperator & WO_AND)!=0 ){
        WhereInfo *pSubWInfo;           /* Info for single OR-term scan */
        Expr *pOrExpr = pOrTerm->pExpr; /* Current OR clause term */
        int j1 = 0;                     /* Address of jump operation */
        if( pAndExpr && !ExprHasProperty(pOrExpr, EP_FromJoin) ){
          pAndExpr->pLeft = pOrExpr;
          pOrExpr = pAndExpr;
        }
        /* Loop through table entries that match term pOrTerm. */

        pSubWInfo = sqlite3WhereBegin(pParse, pOrTab, pOrExpr, 0, 0,
                                      wctrlFlags, iCovCur);
        assert( pSubWInfo || pParse->nErr || db->mallocFailed );
        if( pSubWInfo ){
          WhereLoop *pSubLoop;
          explainOneScan(
              pParse, pOrTab, &pSubWInfo->a[0], iLevel, pLevel->iFrom, 0

      pTerm->wtFlags |= TERM_CODED;
    }
  }

  return pLevel->notReady;
}

#if defined(WHERETRACE_ENABLED) && defined(SQLITE_ENABLE_TREE_EXPLAIN)
/*
** Generate "Explanation" text for a WhereTerm.
*/
static void whereExplainTerm(Vdbe *v, WhereTerm *pTerm){



  char zType[4];
  memcpy(zType, "...", 4);
  if( pTerm->wtFlags & TERM_VIRTUAL ) zType[0] = 'V';
  if( pTerm->eOperator & WO_EQUIV  ) zType[1] = 'E';
  if( ExprHasProperty(pTerm->pExpr, EP_FromJoin) ) zType[2] = 'L';

  sqlite3ExplainPrintf(v, "%s ", zType);

  sqlite3ExplainExpr(v, pTerm->pExpr);
}
#endif /* WHERETRACE_ENABLED && SQLITE_ENABLE_TREE_EXPLAIN */



#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
  WhereInfo *pWInfo = pWC->pWInfo;

  }
  if( p->wsFlags & WHERE_SKIPSCAN ){
    sqlite3DebugPrintf(" f %05x %d-%d", p->wsFlags, p->nLTerm,p->u.btree.nSkip);
  }else{
    sqlite3DebugPrintf(" f %05x N %d", p->wsFlags, p->nLTerm);
  }
  sqlite3DebugPrintf(" cost %d,%d,%d\n", p->rSetup, p->rRun, p->nOut);
#ifdef SQLITE_ENABLE_TREE_EXPLAIN
  /* If the 0x100 bit of wheretracing is set, then show all of the constraint
  ** expressions in the WhereLoop.aLTerm[] array.
  */
  if( p->nLTerm && (sqlite3WhereTrace & 0x100)!=0 ){  /* WHERETRACE 0x100 */
    int i;
    Vdbe *v = pWInfo->pParse->pVdbe;
    sqlite3ExplainBegin(v);
    for(i=0; i<p->nLTerm; i++){
      WhereTerm *pTerm = p->aLTerm[i];
      if( pTerm==0 ) continue;
      sqlite3ExplainPrintf(v, "  (%d) #%-2d ", i+1, (int)(pTerm-pWC->a));
      sqlite3ExplainPush(v);
      whereExplainTerm(v, pTerm);
      sqlite3ExplainPop(v);
      sqlite3ExplainNL(v);
    }
    sqlite3ExplainFinish(v);
    sqlite3DebugPrintf("%s", sqlite3VdbeExplanation(v));
  }
#endif
}
#endif

/*
** Convert bulk memory into a valid WhereLoop that can be passed
** to whereLoopClear harmlessly.
*/

  int iCur;
  WhereClause tempWC;
  WhereLoopBuilder sSubBuild;
  WhereOrSet sSum, sCur;
  struct SrcList_item *pItem;
  
  pWC = pBuilder->pWC;
  if( pWInfo->wctrlFlags & WHERE_AND_ONLY ) return SQLITE_OK;
  pWCEnd = pWC->a + pWC->nTerm;
  pNew = pBuilder->pNew;
  memset(&sSum, 0, sizeof(sSum));
  pItem = pWInfo->pTabList->a + pNew->iTab;
  iCur = pItem->iCursor;

  for(pTerm=pWC->a; pTerm<pWCEnd && rc==SQLITE_OK; pTerm++){
    if( (pTerm->eOperator & WO_OR)!=0
     && (pTerm->u.pOrInfo->indexable & pNew->maskSelf)!=0 
    ){
      WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
      WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
      WhereTerm *pOrTerm;
      int once = 1;
      int i, j;
    
      sSubBuild = *pBuilder;
      sSubBuild.pOrderBy = 0;
      sSubBuild.pOrSet = &sCur;


      for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
        if( (pOrTerm->eOperator & WO_AND)!=0 ){
          sSubBuild.pWC = &pOrTerm->u.pAndInfo->wc;
        }else if( pOrTerm->leftCursor==iCur ){
          tempWC.pWInfo = pWC->pWInfo;
          tempWC.pOuter = pWC;
          tempWC.op = TK_AND;
          tempWC.nTerm = 1;
          tempWC.a = pOrTerm;
          sSubBuild.pWC = &tempWC;
        }else{
          continue;
        }
        sCur.n = 0;









#ifndef SQLITE_OMIT_VIRTUALTABLE
        if( IsVirtual(pItem->pTab) ){
          rc = whereLoopAddVirtual(&sSubBuild, mExtra);
        }else
#endif
        {
          rc = whereLoopAddBtree(&sSubBuild, mExtra);
        }



        assert( rc==SQLITE_OK || sCur.n==0 );
        if( sCur.n==0 ){
          sSum.n = 0;
          break;
        }else if( once ){
          whereOrMove(&sSum, &sCur);
          once = 0;

        ** the planner may elect to "OR" together a full-table scan and an
        ** index lookup. And other similarly odd results.  */
        pNew->rRun = sSum.a[i].rRun + 1;
        pNew->nOut = sSum.a[i].nOut;
        pNew->prereq = sSum.a[i].prereq;
        rc = whereLoopInsert(pBuilder, pNew);
      }

    }
  }
  return rc;
}

/*
** Add all WhereLoop objects for all tables 

      pWInfo->wctrlFlags |= WHERE_DISTINCTBY;
      pWInfo->pOrderBy = pResultSet;
    }
  }

  /* Construct the WhereLoop objects */
  WHERETRACE(0xffff,("*** Optimizer Start ***\n"));

  /* Display all terms of the WHERE clause */
#if defined(WHERETRACE_ENABLED) && defined(SQLITE_ENABLE_TREE_EXPLAIN)
  if( sqlite3WhereTrace & 0x100 ){
    int i;
    Vdbe *v = pParse->pVdbe;
    sqlite3ExplainBegin(v);
    for(i=0; i<sWLB.pWC->nTerm; i++){
      sqlite3ExplainPrintf(v, "#%-2d ", i);
      sqlite3ExplainPush(v);
      whereExplainTerm(v, &sWLB.pWC->a[i]);
      sqlite3ExplainPop(v);
      sqlite3ExplainNL(v);
    }
    sqlite3ExplainFinish(v);
    sqlite3DebugPrintf("%s", sqlite3VdbeExplanation(v));
  }
#endif

  if( nTabList!=1 || whereShortCut(&sWLB)==0 ){
    rc = whereLoopAddAll(&sWLB);
    if( rc ) goto whereBeginError;
  
    /* Display all of the WhereLoop objects if wheretrace is enabled */
#ifdef WHERETRACE_ENABLED /* !=0 */
    if( sqlite3WhereTrace ){

  execsql {
    CREATE TABLE t2(x,y);
    INSERT INTO t2 SELECT x, x+1 FROM t1 WHERE x<5;
    SELECT x, test_eval('DELETE FROM t2 WHERE x='||x), y FROM t2;
  }
} {1 {} {} 2 {} {} 3 {} {} 4 {} {}}
do_test eval-2.2 {












  execsql {
    SELECT * FROM t2
  }
} {}

# Modify a row while it is being read.
#