assert( pCur->eState==CURSOR_VALID );
  assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );

  iCellDepth = pCur->iPage;
  iCellIdx = pCur->aiIdx[iCellDepth];
  pPage = pCur->apPage[iCellDepth];
  pCell = findCell(pPage, iCellIdx);























  /* If the page containing the entry to delete is not a leaf page, move
  ** the cursor to the largest entry in the tree that is smaller than
  ** the entry being deleted. This cell will replace the cell being deleted
  ** from the internal node. The 'previous' entry is used for this instead
  ** of the 'next' entry, as the previous entry is always a part of the
  ** sub-tree headed by the child page of the cell being deleted. This makes
................................................................................

  /* If this is a delete operation to remove a row from a table b-tree,
  ** invalidate any incrblob cursors open on the row being deleted.  */
  if( pCur->pKeyInfo==0 ){
    invalidateIncrblobCursors(p, pCur->info.nKey, 0);
  }

  /* If the bPreserve flag is set to true, then the cursor position must
  ** be preserved following this delete operation. If the current delete
  ** will cause a b-tree rebalance, then this is done by saving the cursor
  ** key and leaving the cursor in CURSOR_REQUIRESEEK state before 
  ** returning. 
  **
  ** Or, if the current delete will not cause a rebalance, then the cursor
  ** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
  ** before or after the deleted entry. In this case set bSkipnext to true.  */
  if( bPreserve ){
    if( !pPage->leaf 
     || (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
    ){
      /* A b-tree rebalance will be required after deleting this entry.
      ** Save the cursor key.  */
      rc = saveCursorKey(pCur);
      if( rc ) return rc;
    }else{
      bSkipnext = 1;
    }
  }

  /* Make the page containing the entry to be deleted writable. Then free any
  ** overflow pages associated with the entry and finally remove the cell
  ** itself from within the page.  */
  rc = sqlite3PagerWrite(pPage->pDbPage);
  if( rc ) return rc;
  rc = clearCell(pPage, pCell, &szCell);
  dropCell(pPage, iCellIdx, szCell, &rc);

  assert( pCur->eState==CURSOR_VALID );
  assert( (flags & ~(BTREE_SAVEPOSITION | BTREE_AUXDELETE))==0 );

  iCellDepth = pCur->iPage;
  iCellIdx = pCur->aiIdx[iCellDepth];
  pPage = pCur->apPage[iCellDepth];
  pCell = findCell(pPage, iCellIdx);

  /* If the bPreserve flag is set to true, then the cursor position must
  ** be preserved following this delete operation. If the current delete
  ** will cause a b-tree rebalance, then this is done by saving the cursor
  ** key and leaving the cursor in CURSOR_REQUIRESEEK state before 
  ** returning. 
  **
  ** Or, if the current delete will not cause a rebalance, then the cursor
  ** will be left in CURSOR_SKIPNEXT state pointing to the entry immediately
  ** before or after the deleted entry. In this case set bSkipnext to true.  */
  if( bPreserve ){
    if( !pPage->leaf 
     || (pPage->nFree+cellSizePtr(pPage,pCell)+2)>(int)(pBt->usableSize*2/3)
    ){
      /* A b-tree rebalance will be required after deleting this entry.
      ** Save the cursor key.  */
      rc = saveCursorKey(pCur);
      if( rc ) return rc;
    }else{
      bSkipnext = 1;
    }
  }

  /* If the page containing the entry to delete is not a leaf page, move
  ** the cursor to the largest entry in the tree that is smaller than
  ** the entry being deleted. This cell will replace the cell being deleted
  ** from the internal node. The 'previous' entry is used for this instead
  ** of the 'next' entry, as the previous entry is always a part of the
  ** sub-tree headed by the child page of the cell being deleted. This makes
................................................................................

  /* If this is a delete operation to remove a row from a table b-tree,
  ** invalidate any incrblob cursors open on the row being deleted.  */
  if( pCur->pKeyInfo==0 ){
    invalidateIncrblobCursors(p, pCur->info.nKey, 0);
  }























  /* Make the page containing the entry to be deleted writable. Then free any
  ** overflow pages associated with the entry and finally remove the cell
  ** itself from within the page.  */
  rc = sqlite3PagerWrite(pPage->pDbPage);
  if( rc ) return rc;
  rc = clearCell(pPage, pCell, &szCell);
  dropCell(pPage, iCellIdx, szCell, &rc);

  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. */
................................................................................
  ** 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;
  sqlite3ExprSetHeightAndFlags(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) */

  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;
  }

  /* 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. */
................................................................................
  ** 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;
  pEList = sqlite3ExprListAppend(pParse, 0, pSelectRowid);
  if( pEList == 0 ) goto limit_where_cleanup;

  /* 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;
  }

  /* 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);

  pInClause = pWhereRowid ? sqlite3PExpr(pParse, TK_IN, pWhereRowid, 0, 0) : 0;




  sqlite3PExprAddSelect(pParse, pInClause, pSelect);
  return pInClause;


limit_where_cleanup:




  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) */

    sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
  }
  if( p ) {
    sqlite3ExprCheckHeight(pParse, p->nHeight);
  }
  return p;
}

















/*
** If the expression is always either TRUE or FALSE (respectively),
** then return 1.  If one cannot determine the truth value of the
** expression at compile-time return 0.
**
** This is an optimization.  If is OK to return 0 here even if

    sqlite3ExprAttachSubtrees(pParse->db, p, pLeft, pRight);
  }
  if( p ) {
    sqlite3ExprCheckHeight(pParse, p->nHeight);
  }
  return p;
}

/*
** Add pSelect to the Expr.x.pSelect field.  Or, if pExpr is NULL (due
** do a memory allocation failure) then delete the pSelect object.
*/
void sqlite3PExprAddSelect(Parse *pParse, Expr *pExpr, Select *pSelect){
  if( pExpr ){
    pExpr->x.pSelect = pSelect;
    ExprSetProperty(pExpr, EP_xIsSelect|EP_Subquery);
    sqlite3ExprSetHeightAndFlags(pParse, pExpr);
  }else{
    assert( pParse->db->mallocFailed );
    sqlite3SelectDelete(pParse->db, pSelect);
  }
}


/*
** If the expression is always either TRUE or FALSE (respectively),
** then return 1.  If one cannot determine the truth value of the
** expression at compile-time return 0.
**
** This is an optimization.  If is OK to return 0 here even if

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  if( (iAmt+iOfst)>p->endpoint.iOffset ){
    return SQLITE_IOERR_SHORT_READ;
  }
#endif

  assert( (iAmt+iOfst)<=p->endpoint.iOffset );

  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite3_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += p->nChunkSize;
    }
  }else{
    pChunk = p->readpoint.pChunk;

  }

  iChunkOffset = (int)(iOfst%p->nChunkSize);
  do {
    int iSpace = p->nChunkSize - iChunkOffset;
    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = iOfst+iAmt;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Free the list of FileChunk structures headed at MemJournal.pFirst.

#ifdef SQLITE_ENABLE_ATOMIC_WRITE
  if( (iAmt+iOfst)>p->endpoint.iOffset ){
    return SQLITE_IOERR_SHORT_READ;
  }
#endif

  assert( (iAmt+iOfst)<=p->endpoint.iOffset );
  assert( p->readpoint.iOffset==0 || p->readpoint.pChunk!=0 );
  if( p->readpoint.iOffset!=iOfst || iOfst==0 ){
    sqlite3_int64 iOff = 0;
    for(pChunk=p->pFirst; 
        ALWAYS(pChunk) && (iOff+p->nChunkSize)<=iOfst;
        pChunk=pChunk->pNext
    ){
      iOff += p->nChunkSize;
    }
  }else{
    pChunk = p->readpoint.pChunk;
    assert( pChunk!=0 );
  }

  iChunkOffset = (int)(iOfst%p->nChunkSize);
  do {
    int iSpace = p->nChunkSize - iChunkOffset;
    int nCopy = MIN(nRead, (p->nChunkSize - iChunkOffset));
    memcpy(zOut, (u8*)pChunk->zChunk + iChunkOffset, nCopy);
    zOut += nCopy;
    nRead -= iSpace;
    iChunkOffset = 0;
  } while( nRead>=0 && (pChunk=pChunk->pNext)!=0 && nRead>0 );
  p->readpoint.iOffset = pChunk ? iOfst+iAmt : 0;
  p->readpoint.pChunk = pChunk;

  return SQLITE_OK;
}

/*
** Free the list of FileChunk structures headed at MemJournal.pFirst.

** routine to lower a locking level.
*/
static int unixLock(sqlite3_file *id, int eFileLock){
  /* The following describes the implementation of the various locks and
  ** lock transitions in terms of the POSIX advisory shared and exclusive
  ** lock primitives (called read-locks and write-locks below, to avoid
  ** confusion with SQLite lock names). The algorithms are complicated
  ** slightly in order to be compatible with windows systems simultaneously
  ** accessing the same database file, in case that is ever required.
  **
  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
  ** byte', each single bytes at well known offsets, and the 'shared byte
  ** range', a range of 510 bytes at a well known offset.
  **
  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
  ** byte'.  If this is successful, a random byte from the 'shared byte
  ** range' is read-locked and the lock on the 'pending byte' released.






  **
  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
  ** A RESERVED lock is implemented by grabbing a write-lock on the
  ** 'reserved byte'. 
  **
  ** A process may only obtain a PENDING lock after it has obtained a
  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
................................................................................
  ** after a crash.
  **
  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
  ** implemented by obtaining a write-lock on the entire 'shared byte
  ** range'. Since all other locks require a read-lock on one of the bytes
  ** within this range, this ensures that no other locks are held on the
  ** database. 
  **
  ** The reason a single byte cannot be used instead of the 'shared byte
  ** range' is that some versions of windows do not support read-locks. By
  ** locking a random byte from a range, concurrent SHARED locks may exist
  ** even if the locking primitive used is always a write-lock.
  */
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  unixInodeInfo *pInode;
  struct flock lock;
  int tErrno = 0;

** routine to lower a locking level.
*/
static int unixLock(sqlite3_file *id, int eFileLock){
  /* The following describes the implementation of the various locks and
  ** lock transitions in terms of the POSIX advisory shared and exclusive
  ** lock primitives (called read-locks and write-locks below, to avoid
  ** confusion with SQLite lock names). The algorithms are complicated
  ** slightly in order to be compatible with Windows95 systems simultaneously
  ** accessing the same database file, in case that is ever required.
  **
  ** Symbols defined in os.h indentify the 'pending byte' and the 'reserved
  ** byte', each single bytes at well known offsets, and the 'shared byte
  ** range', a range of 510 bytes at a well known offset.
  **
  ** To obtain a SHARED lock, a read-lock is obtained on the 'pending
  ** byte'.  If this is successful, 'shared byte range' is read-locked
  ** and the lock on the 'pending byte' released.  (Legacy note:  When
  ** SQLite was first developed, Windows95 systems were still very common,
  ** and Widnows95 lacks a shared-lock capability.  So on Windows95, a
  ** single randomly selected by from the 'shared byte range' is locked.
  ** Windows95 is now pretty much extinct, but this work-around for the
  ** lack of shared-locks on Windows95 lives on, for backwards
  ** compatibility.)
  **
  ** A process may only obtain a RESERVED lock after it has a SHARED lock.
  ** A RESERVED lock is implemented by grabbing a write-lock on the
  ** 'reserved byte'. 
  **
  ** A process may only obtain a PENDING lock after it has obtained a
  ** SHARED lock. A PENDING lock is implemented by obtaining a write-lock
................................................................................
  ** after a crash.
  **
  ** An EXCLUSIVE lock, obtained after a PENDING lock is held, is
  ** implemented by obtaining a write-lock on the entire 'shared byte
  ** range'. Since all other locks require a read-lock on one of the bytes
  ** within this range, this ensures that no other locks are held on the
  ** database. 





  */
  int rc = SQLITE_OK;
  unixFile *pFile = (unixFile*)id;
  unixInodeInfo *pInode;
  struct flock lock;
  int tErrno = 0;

  Expr *temp4 = sqlite3PExpr(pParse, TK_DOT, temp2, temp3, 0);
  spanSet(&A,&X,&Z); /*A-overwrites-X*/
  A.pExpr = sqlite3PExpr(pParse, TK_DOT, temp1, temp4, 0);
}
term(A) ::= INTEGER|FLOAT|BLOB(X). {spanExpr(&A,pParse,@X,X);/*A-overwrites-X*/}
term(A) ::= STRING(X).             {spanExpr(&A,pParse,@X,X);/*A-overwrites-X*/}
expr(A) ::= VARIABLE(X).     {
  Token t = X; /*A-overwrites-X*/
  if( t.n>=2 && t.z[0]=='#' && sqlite3Isdigit(t.z[1]) ){



    /* When doing a nested parse, one can include terms in an expression
    ** that look like this:   #1 #2 ...  These terms refer to registers
    ** in the virtual machine.  #N is the N-th register. */


    spanSet(&A, &t, &t);
    if( pParse->nested==0 ){
      sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &t);
      A.pExpr = 0;
    }else{
      A.pExpr = sqlite3PExpr(pParse, TK_REGISTER, 0, 0, &t);
      if( A.pExpr ) sqlite3GetInt32(&t.z[1], &A.pExpr->iTable);
    }
  }else{
    spanExpr(&A, pParse, TK_VARIABLE, t);
    sqlite3ExprAssignVarNumber(pParse, A.pExpr);
  }
}
expr(A) ::= expr(A) COLLATE ids(C). {
  A.pExpr = sqlite3ExprAddCollateToken(pParse, A.pExpr, &C, 1);
  A.zEnd = &C.z[C.n];
}
%ifndef SQLITE_OMIT_CAST
................................................................................
      exprNot(pParse, N, &A);
    }
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= LP(B) select(X) RP(E). {
    spanSet(&A,&B,&E); /*A-overwrites-B*/
    A.pExpr = sqlite3PExpr(pParse, TK_SELECT, 0, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = X;
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeightAndFlags(pParse, A.pExpr);
    }else{
      sqlite3SelectDelete(pParse->db, X);
    }
  }
  expr(A) ::= expr(A) in_op(N) LP select(Y) RP(E).  [IN] {
    A.pExpr = sqlite3PExpr(pParse, TK_IN, A.pExpr, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = Y;
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeightAndFlags(pParse, A.pExpr);
    }else{
      sqlite3SelectDelete(pParse->db, Y);
    }
    exprNot(pParse, N, &A);
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= expr(A) in_op(N) nm(Y) dbnm(Z). [IN] {
    SrcList *pSrc = sqlite3SrcListAppend(pParse->db, 0,&Y,&Z);

    A.pExpr = sqlite3PExpr(pParse, TK_IN, A.pExpr, 0, 0);
    if( A.pExpr ){
      A.pExpr->x.pSelect = sqlite3SelectNew(pParse, 0,pSrc,0,0,0,0,0,0,0);
      ExprSetProperty(A.pExpr, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeightAndFlags(pParse, A.pExpr);
    }else{
      sqlite3SrcListDelete(pParse->db, pSrc);
    }
    exprNot(pParse, N, &A);
    A.zEnd = Z.z ? &Z.z[Z.n] : &Y.z[Y.n];
  }
  expr(A) ::= EXISTS(B) LP select(Y) RP(E). {
    Expr *p;
    spanSet(&A,&B,&E); /*A-overwrites-B*/
    p = A.pExpr = sqlite3PExpr(pParse, TK_EXISTS, 0, 0, 0);
    if( p ){
      p->x.pSelect = Y;
      ExprSetProperty(p, EP_xIsSelect|EP_Subquery);
      sqlite3ExprSetHeightAndFlags(pParse, p);
    }else{
      sqlite3SelectDelete(pParse->db, Y);
    }
  }
%endif SQLITE_OMIT_SUBQUERY

/* CASE expressions */
expr(A) ::= CASE(C) case_operand(X) case_exprlist(Y) case_else(Z) END(E). {
  spanSet(&A,&C,&E);  /*A-overwrites-C*/
  A.pExpr = sqlite3PExpr(pParse, TK_CASE, X, 0, 0);

  Expr *temp4 = sqlite3PExpr(pParse, TK_DOT, temp2, temp3, 0);
  spanSet(&A,&X,&Z); /*A-overwrites-X*/
  A.pExpr = sqlite3PExpr(pParse, TK_DOT, temp1, temp4, 0);
}
term(A) ::= INTEGER|FLOAT|BLOB(X). {spanExpr(&A,pParse,@X,X);/*A-overwrites-X*/}
term(A) ::= STRING(X).             {spanExpr(&A,pParse,@X,X);/*A-overwrites-X*/}
expr(A) ::= VARIABLE(X).     {

  if( !(X.z[0]=='#' && sqlite3Isdigit(X.z[1])) ){
    spanExpr(&A, pParse, TK_VARIABLE, X);
    sqlite3ExprAssignVarNumber(pParse, A.pExpr);
  }else{
    /* When doing a nested parse, one can include terms in an expression
    ** that look like this:   #1 #2 ...  These terms refer to registers
    ** in the virtual machine.  #N is the N-th register. */
    Token t = X; /*A-overwrites-X*/
    assert( t.n>=2 );
    spanSet(&A, &t, &t);
    if( pParse->nested==0 ){
      sqlite3ErrorMsg(pParse, "near \"%T\": syntax error", &t);
      A.pExpr = 0;
    }else{
      A.pExpr = sqlite3PExpr(pParse, TK_REGISTER, 0, 0, &t);
      if( A.pExpr ) sqlite3GetInt32(&t.z[1], &A.pExpr->iTable);
    }



  }
}
expr(A) ::= expr(A) COLLATE ids(C). {
  A.pExpr = sqlite3ExprAddCollateToken(pParse, A.pExpr, &C, 1);
  A.zEnd = &C.z[C.n];
}
%ifndef SQLITE_OMIT_CAST
................................................................................
      exprNot(pParse, N, &A);
    }
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= LP(B) select(X) RP(E). {
    spanSet(&A,&B,&E); /*A-overwrites-B*/
    A.pExpr = sqlite3PExpr(pParse, TK_SELECT, 0, 0, 0);



    sqlite3PExprAddSelect(pParse, A.pExpr, X);



  }
  expr(A) ::= expr(A) in_op(N) LP select(Y) RP(E).  [IN] {
    A.pExpr = sqlite3PExpr(pParse, TK_IN, A.pExpr, 0, 0);



    sqlite3PExprAddSelect(pParse, A.pExpr, Y);



    exprNot(pParse, N, &A);
    A.zEnd = &E.z[E.n];
  }
  expr(A) ::= expr(A) in_op(N) nm(Y) dbnm(Z). [IN] {
    SrcList *pSrc = sqlite3SrcListAppend(pParse->db, 0,&Y,&Z);
    Select *pSelect = sqlite3SelectNew(pParse, 0,pSrc,0,0,0,0,0,0,0);
    A.pExpr = sqlite3PExpr(pParse, TK_IN, A.pExpr, 0, 0);

    sqlite3PExprAddSelect(pParse, A.pExpr, pSelect);





    exprNot(pParse, N, &A);
    A.zEnd = Z.z ? &Z.z[Z.n] : &Y.z[Y.n];
  }
  expr(A) ::= EXISTS(B) LP select(Y) RP(E). {
    Expr *p;
    spanSet(&A,&B,&E); /*A-overwrites-B*/
    p = A.pExpr = sqlite3PExpr(pParse, TK_EXISTS, 0, 0, 0);
    sqlite3PExprAddSelect(pParse, p, Y);






  }
%endif SQLITE_OMIT_SUBQUERY

/* CASE expressions */
expr(A) ::= CASE(C) case_operand(X) case_exprlist(Y) case_else(Z) END(E). {
  spanSet(&A,&C,&E);  /*A-overwrites-C*/
  A.pExpr = sqlite3PExpr(pParse, TK_CASE, X, 0, 0);

  sqlite3_snapshot **ppSnapshot
);

/*
** CAPI3REF: Start a read transaction on an historical snapshot
** EXPERIMENTAL
**
** ^The [sqlite3_snapshot_open(D,S,P)] interface attempts to move the
** read transaction that is currently open on schema S of

** [database connection] D so that it refers to historical [snapshot] P.

** ^The [sqlite3_snapshot_open()] interface returns SQLITE_OK on success
** or an appropriate [error code] if it fails.
**
** ^In order to succeed, a call to [sqlite3_snapshot_open(D,S,P)] must be
** the first operation, apart from other sqlite3_snapshot_open() calls,
** following the [BEGIN] that starts a new read transaction.




** ^A [snapshot] will fail to open if it has been overwritten by a 
** [checkpoint].
** ^A [snapshot] will fail to open if the database connection D has not
** previously completed at least one read operation against the database 






** file.  (Hint: Run "[PRAGMA application_id]" against a newly opened
** database connection in order to make it ready to use snapshots.)
**
** The [sqlite3_snapshot_open()] interface is only available when the
** SQLITE_ENABLE_SNAPSHOT compile-time option is used.
*/
SQLITE_EXPERIMENTAL int sqlite3_snapshot_open(
  sqlite3 *db,

  sqlite3_snapshot **ppSnapshot
);

/*
** CAPI3REF: Start a read transaction on an historical snapshot
** EXPERIMENTAL
**
** ^The [sqlite3_snapshot_open(D,S,P)] interface starts a
** read transaction for schema S of
** [database connection] D such that the read transaction
** refers to historical [snapshot] P, rather than the most
** recent change to the database.
** ^The [sqlite3_snapshot_open()] interface returns SQLITE_OK on success
** or an appropriate [error code] if it fails.
**
** ^In order to succeed, a call to [sqlite3_snapshot_open(D,S,P)] must be

** the first operation following the [BEGIN] that takes the schema S
** out of [autocommit mode].
** ^In other words, schema S must not currently be in
** a transaction for [sqlite3_snapshot_open(D,S,P)] to work, but the
** database connection D must be out of [autocommit mode].
** ^A [snapshot] will fail to open if it has been overwritten by a
** [checkpoint].


** ^(A call to [sqlite3_snapshot_open(D,S,P)] will fail if the
** database connection D does not know that the database file for
** schema S is in [WAL mode].  A database connection might not know
** that the database file is in [WAL mode] if there has been no prior
** I/O on that database connection, or if the database entered [WAL mode] 
** after the most recent I/O on the database connection.)^
** (Hint: Run "[PRAGMA application_id]" against a newly opened
** database connection in order to make it ready to use snapshots.)
**
** The [sqlite3_snapshot_open()] interface is only available when the
** SQLITE_ENABLE_SNAPSHOT compile-time option is used.
*/
SQLITE_EXPERIMENTAL int sqlite3_snapshot_open(
  sqlite3 *db,

#ifdef SQLITE_DEBUG
int sqlite3NoTempsInRange(Parse*,int,int);
#endif
Expr *sqlite3ExprAlloc(sqlite3*,int,const Token*,int);
Expr *sqlite3Expr(sqlite3*,int,const char*);
void sqlite3ExprAttachSubtrees(sqlite3*,Expr*,Expr*,Expr*);
Expr *sqlite3PExpr(Parse*, int, Expr*, Expr*, const Token*);

Expr *sqlite3ExprAnd(sqlite3*,Expr*, Expr*);
Expr *sqlite3ExprFunction(Parse*,ExprList*, Token*);
void sqlite3ExprAssignVarNumber(Parse*, Expr*);
void sqlite3ExprDelete(sqlite3*, Expr*);
ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
void sqlite3ExprListSetSortOrder(ExprList*,int);
void sqlite3ExprListSetName(Parse*,ExprList*,Token*,int);

#ifdef SQLITE_DEBUG
int sqlite3NoTempsInRange(Parse*,int,int);
#endif
Expr *sqlite3ExprAlloc(sqlite3*,int,const Token*,int);
Expr *sqlite3Expr(sqlite3*,int,const char*);
void sqlite3ExprAttachSubtrees(sqlite3*,Expr*,Expr*,Expr*);
Expr *sqlite3PExpr(Parse*, int, Expr*, Expr*, const Token*);
void sqlite3PExprAddSelect(Parse*, Expr*, Select*);
Expr *sqlite3ExprAnd(sqlite3*,Expr*, Expr*);
Expr *sqlite3ExprFunction(Parse*,ExprList*, Token*);
void sqlite3ExprAssignVarNumber(Parse*, Expr*);
void sqlite3ExprDelete(sqlite3*, Expr*);
ExprList *sqlite3ExprListAppend(Parse*,ExprList*,Expr*);
void sqlite3ExprListSetSortOrder(ExprList*,int);
void sqlite3ExprListSetName(Parse*,ExprList*,Token*,int);

** Convert a LogEst into an integer.
**
** Note that this routine is only used when one or more of various
** non-standard compile-time options is enabled.
*/
u64 sqlite3LogEstToInt(LogEst x){
  u64 n;
  if( x<10 ) return 1;
  n = x%10;
  x /= 10;
  if( n>=5 ) n -= 2;
  else if( n>=1 ) n -= 1;
#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || \
    defined(SQLITE_EXPLAIN_ESTIMATED_ROWS)
  if( x>60 ) return (u64)LARGEST_INT64;

** Convert a LogEst into an integer.
**
** Note that this routine is only used when one or more of various
** non-standard compile-time options is enabled.
*/
u64 sqlite3LogEstToInt(LogEst x){
  u64 n;

  n = x%10;
  x /= 10;
  if( n>=5 ) n -= 2;
  else if( n>=1 ) n -= 1;
#if defined(SQLITE_ENABLE_STMT_SCANSTATUS) || \
    defined(SQLITE_EXPLAIN_ESTIMATED_ROWS)
  if( x>60 ) return (u64)LARGEST_INT64;

        len -= pRec->u.nZero;
      }
    }
    nData += len;
    testcase( serial_type==127 );
    testcase( serial_type==128 );
    nHdr += serial_type<=127 ? 1 : sqlite3VarintLen(serial_type);


  }while( (--pRec)>=pData0 );

  /* EVIDENCE-OF: R-22564-11647 The header begins with a single varint
  ** which determines the total number of bytes in the header. The varint
  ** value is the size of the header in bytes including the size varint
  ** itself. */
  testcase( nHdr==126 );
  testcase( nHdr==127 );

        len -= pRec->u.nZero;
      }
    }
    nData += len;
    testcase( serial_type==127 );
    testcase( serial_type==128 );
    nHdr += serial_type<=127 ? 1 : sqlite3VarintLen(serial_type);
    if( pRec==pData0 ) break;
    pRec--;
  }while(1);

  /* EVIDENCE-OF: R-22564-11647 The header begins with a single varint
  ** which determines the total number of bytes in the header. The varint
  ** value is the size of the header in bytes including the size varint
  ** itself. */
  testcase( nHdr==126 );
  testcase( nHdr==127 );

static void vdbeFreeOpArray(sqlite3 *, Op *, int);

/*
** Delete a P4 value if necessary.
*/
static void freeP4(sqlite3 *db, int p4type, void *p4){
  if( p4 ){
    assert( db );
    switch( p4type ){
      case P4_FUNCCTX: {
        freeEphemeralFunction(db, ((sqlite3_context*)p4)->pFunc);
        /* Fall through into the next case */
      }
      case P4_REAL:
      case P4_INT64:
      case P4_DYNAMIC:
      case P4_INTARRAY: {
        sqlite3DbFree(db, p4);
        break;
      }
      case P4_KEYINFO: {
        if( db->pnBytesFreed==0 ) sqlite3KeyInfoUnref((KeyInfo*)p4);
        break;
      }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
      case P4_EXPR: {
        sqlite3ExprDelete(db, (Expr*)p4);
        break;
      }
#endif
      case P4_MPRINTF: {
        if( db->pnBytesFreed==0 ) sqlite3_free(p4);
        break;
      }
      case P4_FUNCDEF: {
        freeEphemeralFunction(db, (FuncDef*)p4);
        break;
      }
      case P4_MEM: {
        if( db->pnBytesFreed==0 ){
          sqlite3ValueFree((sqlite3_value*)p4);
        }else{
          Mem *p = (Mem*)p4;
          if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
          sqlite3DbFree(db, p);
        }
        break;
      }
      case P4_VTAB : {
        if( db->pnBytesFreed==0 ) sqlite3VtabUnlock((VTable *)p4);
        break;
      }
    }
  }
}

/*
** Free the space allocated for aOp and any p4 values allocated for the
** opcodes contained within. If aOp is not NULL it is assumed to contain 

static void vdbeFreeOpArray(sqlite3 *, Op *, int);

/*
** Delete a P4 value if necessary.
*/
static void freeP4(sqlite3 *db, int p4type, void *p4){

  assert( db );
  switch( p4type ){
    case P4_FUNCCTX: {
      freeEphemeralFunction(db, ((sqlite3_context*)p4)->pFunc);
      /* Fall through into the next case */
    }
    case P4_REAL:
    case P4_INT64:
    case P4_DYNAMIC:
    case P4_INTARRAY: {
      sqlite3DbFree(db, p4);
      break;
    }
    case P4_KEYINFO: {
      if( db->pnBytesFreed==0 ) sqlite3KeyInfoUnref((KeyInfo*)p4);
      break;
    }
#ifdef SQLITE_ENABLE_CURSOR_HINTS
    case P4_EXPR: {
      sqlite3ExprDelete(db, (Expr*)p4);
      break;
    }
#endif
    case P4_MPRINTF: {
      if( db->pnBytesFreed==0 ) sqlite3_free(p4);
      break;
    }
    case P4_FUNCDEF: {
      freeEphemeralFunction(db, (FuncDef*)p4);
      break;
    }
    case P4_MEM: {
      if( db->pnBytesFreed==0 ){
        sqlite3ValueFree((sqlite3_value*)p4);
      }else{
        Mem *p = (Mem*)p4;
        if( p->szMalloc ) sqlite3DbFree(db, p->zMalloc);
        sqlite3DbFree(db, p);
      }
      break;
    }
    case P4_VTAB : {
      if( db->pnBytesFreed==0 ) sqlite3VtabUnlock((VTable *)p4);
      break;

    }
  }
}

/*
** Free the space allocated for aOp and any p4 values allocated for the
** opcodes contained within. If aOp is not NULL it is assumed to contain 

#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
  WhereInfo *pWInfo = pWC->pWInfo;
  int nb = 1+(pWInfo->pTabList->nSrc+7)/8;
  struct SrcList_item *pItem = pWInfo->pTabList->a + p->iTab;
  Table *pTab = pItem->pTab;

  sqlite3DebugPrintf("%c%2d.%0*llx.%0*llx", p->cId,
                     p->iTab, nb, p->maskSelf, nb, p->prereq);
  sqlite3DebugPrintf(" %12s",
                     pItem->zAlias ? pItem->zAlias : pTab->zName);
  if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
    const char *zName;
    if( p->u.btree.pIndex && (zName = p->u.btree.pIndex->zName)!=0 ){
      if( strncmp(zName, "sqlite_autoindex_", 17)==0 ){
        int i = sqlite3Strlen30(zName) - 1;

#ifdef WHERETRACE_ENABLED
/*
** Print a WhereLoop object for debugging purposes
*/
static void whereLoopPrint(WhereLoop *p, WhereClause *pWC){
  WhereInfo *pWInfo = pWC->pWInfo;
  int nb = 1+(pWInfo->pTabList->nSrc+3)/4;
  struct SrcList_item *pItem = pWInfo->pTabList->a + p->iTab;
  Table *pTab = pItem->pTab;
  Bitmask mAll = (((Bitmask)1)<<(nb*4)) - 1;
  sqlite3DebugPrintf("%c%2d.%0*llx.%0*llx", p->cId,
                     p->iTab, nb, p->maskSelf, nb, p->prereq & mAll);
  sqlite3DebugPrintf(" %12s",
                     pItem->zAlias ? pItem->zAlias : pTab->zName);
  if( (p->wsFlags & WHERE_VIRTUALTABLE)==0 ){
    const char *zName;
    if( p->u.btree.pIndex && (zName = p->u.btree.pIndex->zName)!=0 ){
      if( strncmp(zName, "sqlite_autoindex_", 17)==0 ){
        int i = sqlite3Strlen30(zName) - 1;

            sqlite3ExprIfFalse(pParse, pCompare, pLevel->addrCont, 0);
          }
          pCompare->pLeft = 0;
          sqlite3ExprDelete(db, pCompare);
        }
      }
    }





    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);

    sqlite3ExprCachePop(pParse);
  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( (pLoop->wsFlags & WHERE_IPK)!=0
   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
  ){

            sqlite3ExprIfFalse(pParse, pCompare, pLevel->addrCont, 0);
          }
          pCompare->pLeft = 0;
          sqlite3ExprDelete(db, pCompare);
        }
      }
    }
    /* These registers need to be preserved in case there is an IN operator
    ** loop.  So we could deallocate the registers here (and potentially
    ** reuse them later) if (pLoop->wsFlags & WHERE_IN_ABLE)==0.  But it seems
    ** simpler and safer to simply not reuse the registers.
    **
    **    sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
    */
    sqlite3ExprCachePop(pParse);
  }else
#endif /* SQLITE_OMIT_VIRTUALTABLE */

  if( (pLoop->wsFlags & WHERE_IPK)!=0
   && (pLoop->wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_EQ))!=0
  ){

    0 0 0 {USE TEMP B-TREE FOR ORDER BY}
  }

  do_eqp_test 2.2.$mode.6 { 
    SELECT rowid FROM t1 WHERE a IN ('one', 'four') ORDER BY +rowid
  } $plan($mode)
}












































































































finish_test

    0 0 0 {USE TEMP B-TREE FOR ORDER BY}
  }

  do_eqp_test 2.2.$mode.6 { 
    SELECT rowid FROM t1 WHERE a IN ('one', 'four') ORDER BY +rowid
  } $plan($mode)
}

# 2016-04-09.
# Demonstrate a register overwrite problem when using two virtual
# tables where the outer loop uses the IN operator.
#
set G(collist) [list PrimaryKey flagA columnA]
set G(cols) [join $G(collist) ,]
set G(nulls) "NULL"

proc vtab_command {method args} {
  global G

  switch -- $method {
    xConnect {
      return "CREATE TABLE t1($G(cols))"
    }

    xBestIndex {
      set clist [lindex $args 0]
      #puts $clist
      set W [list]
      set U [list]

      set i 0
      for {set idx 0} {$idx < [llength $clist]} {incr idx} {
        array set c [lindex $clist $idx]
        if {$c(op)=="eq" && $c(usable)} {
          lappend W "[lindex $G(collist) $c(column)] = %$i%"
          lappend U use $idx
          incr i
        }
      }

      if {$W==""} {
        set sql "SELECT rowid, * FROM t1"
      } else {
        set sql "SELECT rowid, * FROM t1 WHERE [join $W { AND }]"
      }

      return [concat [list idxstr $sql] $U]
    }

    xFilter {
      foreach {idxnum idxstr vals} $args {}

      set map [list]
      for {set i 0} {$i < [llength $vals]} {incr i} {
        lappend map "%$i%" 
        set v [lindex $vals $i]
        if {[string is integer $v]} { 
          lappend map $v 
        } else {
          lappend map "'$v'"
        }
      }
      set sql [string map $map $idxstr]

      #puts "SQL: $sql"
      return [list sql $sql]
    }
  }

  return {}
}

db close
forcedelete test.db
sqlite3 db test.db
register_tcl_module db

do_execsql_test 3.1 "
  CREATE TABLE t1($G(cols));
  INSERT INTO t1 VALUES(1, 0, 'ValueA');
  INSERT INTO t1 VALUES(2, 0, 'ValueA');
  INSERT INTO t1 VALUES(3, 0, 'ValueB');
  INSERT INTO t1 VALUES(4, 0, 'ValueB');
"

do_execsql_test 3.2 {
  CREATE VIRTUAL TABLE VirtualTableA USING tcl(vtab_command);
  CREATE VIRTUAL TABLE VirtualTableB USING tcl(vtab_command);
}

do_execsql_test 3.3 { SELECT primarykey FROM VirtualTableA } {1 2 3 4}

do_execsql_test 3.4 {
  SELECT * FROM 
  VirtualTableA a CROSS JOIN VirtualTableB b ON b.PrimaryKey=a.PrimaryKey
  WHERE a.ColumnA IN ('ValueA', 'ValueB') AND a.FlagA=0
} {
  1 0 ValueA 1 0 ValueA
  2 0 ValueA 2 0 ValueA
  3 0 ValueB 3 0 ValueB
  4 0 ValueB 4 0 ValueB
}

do_execsql_test 3.5 {
  SELECT * FROM 
  VirtualTableA a CROSS JOIN VirtualTableB b ON b.PrimaryKey=a.PrimaryKey
  WHERE a.FlagA=0 AND a.ColumnA IN ('ValueA', 'ValueB') 
} {
  1 0 ValueA 1 0 ValueA
  2 0 ValueA 2 0 ValueA
  3 0 ValueB 3 0 ValueB
  4 0 ValueB 4 0 ValueB
}


finish_test

  INSERT INTO t4 VALUES(14, 'abcde','xyzzy');
  CREATE INDEX idx_t4_3 ON t4 (col0);
  CREATE INDEX idx_t4_0 ON t4 (col1, col0);
  DELETE FROM t4 WHERE col0=69 OR col0>7;
  PRAGMA integrity_check;
} {ok}
























finish_test

  INSERT INTO t4 VALUES(14, 'abcde','xyzzy');
  CREATE INDEX idx_t4_3 ON t4 (col0);
  CREATE INDEX idx_t4_0 ON t4 (col1, col0);
  DELETE FROM t4 WHERE col0=69 OR col0>7;
  PRAGMA integrity_check;
} {ok}

# 2016-04-09
# Ticket https://sqlite.org/src/info/a306e56ff68b8fa5
# Failure to completely delete when reverse_unordered_selects is
# engaged.
#
db close
forcedelete test.db
sqlite3 db test.db
do_execsql_test 5.0 {
  PRAGMA page_size=1024;
  CREATE TABLE t1(a INTEGER PRIMARY KEY, b, c);
  CREATE INDEX x1 ON t1(b, c);
  INSERT INTO t1(a,b,c) VALUES(1, 1, zeroblob(80));
  INSERT INTO t1(a,b,c) SELECT a+1, 1, c FROM t1;
  INSERT INTO t1(a,b,c) SELECT a+2, 1, c FROM t1;
  INSERT INTO t1(a,b,c) SELECT a+10, 2, c FROM t1 WHERE b=1;
  INSERT INTO t1(a,b,c) SELECT a+20, 3, c FROM t1 WHERE b=1;
  PRAGMA reverse_unordered_selects = ON;
  DELETE FROM t1 WHERE b=2;
  SELECT a FROM t1 WHERE b=2;
} {}


finish_test

        INSERT INTO t2 VALUES($a,$b,$c);
        ROLLBACK TO x2;
      }
    }
  } msg]
  list $rc $msg [db eval {SELECT * FROM t2}]
} {1 {abort due to ROLLBACK} {}}



































finish_test

        INSERT INTO t2 VALUES($a,$b,$c);
        ROLLBACK TO x2;
      }
    }
  } msg]
  list $rc $msg [db eval {SELECT * FROM t2}]
} {1 {abort due to ROLLBACK} {}}

# Ticket: https://www.sqlite.org/src/tktview/7f7f8026eda387d544b
# Segfault in the in-memory journal logic triggered by a tricky
# combination of SAVEPOINT operations.
#
unset -nocomplain i
for {set i 248} {$i<=253} {incr i} {
  do_test savepoint7-3.$i {
    db close
    forcedelete test.db
    sqlite3 db test.db
    db eval {
      PRAGMA page_size=1024;
      PRAGMA temp_store=MEMORY;
      BEGIN;
      CREATE TABLE t1(x INTEGER PRIMARY KEY, y TEXT);
      WITH RECURSIVE c(x) AS (VALUES(1) UNION SELECT x+1 FROM c WHERE x<$::i)
      INSERT INTO t1(x,y) SELECT x*10, printf('%04d%.800c',x,'*') FROM c;
      SAVEPOINT one;
        SELECT count(*) FROM t1;
        WITH RECURSIVE c(x) AS (VALUES(1) UNION SELECT x+1 FROM c WHERE x<$::i)
        INSERT INTO t1(x,y) SELECT x*10+1, printf('%04d%.800c',x,'*') FROM c;
      ROLLBACK TO one;
        SELECT count(*) FROM t1;
        SAVEPOINT twoB;
          WITH RECURSIVE c(x) AS (VALUES(1) UNION SELECT x+1 FROM c WHERE x<10)
          INSERT INTO t1(x,y) SELECT x*10+2, printf('%04d%.800c',x,'*') FROM c;
        ROLLBACK TO twoB;
      RELEASE one;
      COMMIT;
    }
  } [list $i $i]
}


finish_test