**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.123 2004/05/19 20:41:03 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

char const *sqlite3AffinityString(char affinity){
  switch( affinity ){
    case SQLITE_AFF_INTEGER: return "i";
................................................................................
  }
  if( pExpr->op==TK_SELECT ){
    return sqlite3ExprAffinity(pExpr->pSelect->pEList->a[0].pExpr);
  }
  return pExpr->affinity;
}






char sqlite3CompareAffinity(Expr *pExpr, char aff2){
  char aff1 = sqlite3ExprAffinity(pExpr);
  if( aff1 && aff2 ){
    /* Both sides of the comparison are columns. If one has numeric or
    ** integer affinity, use that. Otherwise use no affinity.
    */
    if( aff1==SQLITE_AFF_INTEGER || aff2==SQLITE_AFF_INTEGER ){
................................................................................
    return SQLITE_AFF_NUMERIC;
  }else{
    /* One side is a column, the other is not. Use the columns affinity. */
    return (aff1 + aff2);
  }
}





static char comparisonAffinity(Expr *pExpr){
  char aff;
  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
          pExpr->op==TK_NE );
  assert( pExpr->pLeft );
  aff = sqlite3ExprAffinity(pExpr->pLeft);

**    May you find forgiveness for yourself and forgive others.
**    May you share freely, never taking more than you give.
**
*************************************************************************
** This file contains routines used for analyzing expressions and
** for generating VDBE code that evaluates expressions in SQLite.
**
** $Id: expr.c,v 1.124 2004/05/20 13:54:54 drh Exp $
*/
#include "sqliteInt.h"
#include <ctype.h>

char const *sqlite3AffinityString(char affinity){
  switch( affinity ){
    case SQLITE_AFF_INTEGER: return "i";
................................................................................
  }
  if( pExpr->op==TK_SELECT ){
    return sqlite3ExprAffinity(pExpr->pSelect->pEList->a[0].pExpr);
  }
  return pExpr->affinity;
}

/*
** pExpr is the left operand of a comparison operator.  aff2 is the
** type affinity of the right operand.  This routine returns the
** type affinity that should be used for the comparison operator.
*/
char sqlite3CompareAffinity(Expr *pExpr, char aff2){
  char aff1 = sqlite3ExprAffinity(pExpr);
  if( aff1 && aff2 ){
    /* Both sides of the comparison are columns. If one has numeric or
    ** integer affinity, use that. Otherwise use no affinity.
    */
    if( aff1==SQLITE_AFF_INTEGER || aff2==SQLITE_AFF_INTEGER ){
................................................................................
    return SQLITE_AFF_NUMERIC;
  }else{
    /* One side is a column, the other is not. Use the columns affinity. */
    return (aff1 + aff2);
  }
}

/*
** pExpr is a comparison operator.  Return the type affinity that should
** be applied to both operands prior to doing the comparison.
*/
static char comparisonAffinity(Expr *pExpr){
  char aff;
  assert( pExpr->op==TK_EQ || pExpr->op==TK_IN || pExpr->op==TK_LT ||
          pExpr->op==TK_GT || pExpr->op==TK_GE || pExpr->op==TK_LE ||
          pExpr->op==TK_NE );
  assert( pExpr->pLeft );
  aff = sqlite3ExprAffinity(pExpr->pLeft);

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.307 2004/05/20 02:42:17 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
................................................................................
  }else{
    if( pOp->p1 ) popStack(&pTos, 1);
    pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: Eq P1 P2 *
**
** Pop the top two elements from the stack.  If they are equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
................................................................................
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.
**


*/
/* Opcode: Ne P1 P2 *
**
** Pop the top two elements from the stack.  If they are not equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.
*/
/* Opcode: Lt P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the
** next on stack) is less than the first (the top of stack), then
** jump to instruction P2.  Otherwise, continue to the next instruction.
** In other words, jump if NOS<TOS.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.



*/
/* Opcode: Le P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the

** next on stack) is less than or equal to the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS<=TOS.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.

*/
/* Opcode: Gt P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the
** next on stack) is greater than the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS>TOS.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.



*/
/* Opcode: Ge P1 P2 *
**
** Pop the top two elements from the stack.  If second element (the next

** on stack) is greater than or equal to the first (the top of stack),
** then jump to instruction P2. In other words, jump if NOS>=TOS.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
**
** The second least significant byte of P1 must be an affinity character -
** 'n', 't', 'i' or 'o' - or 0x00. An attempt is made to coerce both values
** according to the affinity before the comparison is made. If the byte is
** 0x00, then numeric affinity is used.
**
** Once any conversions have taken place, and neither value is NULL, 
** the values are compared. If both values are blobs, or both are text,
** then memcmp() is used to determine the results of the comparison. If
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.

*/
case OP_Eq:
case OP_Ne:
case OP_Lt:
case OP_Le:
case OP_Gt:
case OP_Ge: {
................................................................................
  }

  affinity = (pOp->p1>>8)&0xFF;
  if( affinity=='\0' ) affinity = 'n';
  applyAffinity(pNos, affinity);
  applyAffinity(pTos, affinity);


  res = sqlite3MemCompare(pNos, pTos);
  switch( pOp->opcode ){
    case OP_Eq:    res = res==0;     break;
    case OP_Ne:    res = res!=0;     break;
    case OP_Lt:    res = res<0;      break;
    case OP_Le:    res = res<=0;     break;
    case OP_Gt:    res = res>0;      break;
    default:       res = res>=0;     break;

**
** Various scripts scan this source file in order to generate HTML
** documentation, headers files, or other derived files.  The formatting
** of the code in this file is, therefore, important.  See other comments
** in this file for details.  If in doubt, do not deviate from existing
** commenting and indentation practices when changing or adding code.
**
** $Id: vdbe.c,v 1.308 2004/05/20 13:54:54 drh Exp $
*/
#include "sqliteInt.h"
#include "os.h"
#include <ctype.h>
#include "vdbeInt.h"

/*
................................................................................
  }else{
    if( pOp->p1 ) popStack(&pTos, 1);
    pc = pOp->p2 - 1;
  }
  break;
}

/* Opcode: Eq P1 P2 P3
**
** Pop the top two elements from the stack.  If they are equal, then
** jump to instruction P2.  Otherwise, continue to the next instruction.
**
** The least significant byte of P1 may be either 0x00 or 0x01. If either
** operand is NULL (and thus if the result is unknown) then take the jump
** only if the least significant byte of P1 is 0x01.
................................................................................
** both values are numeric, then a numeric comparison is used. If the
** two values are of different types, then they are inequal.
**
** If P2 is zero, do not jump.  Instead, push an integer 1 onto the
** stack if the jump would have been taken, or a 0 if not.  Push a
** NULL if either operand was NULL.
**
** If P3 is not NULL it is a pointer to a collating sequence (a CollSeq
** structure) that defines how to compare text.
*/
/* Opcode: Ne P1 P2 P3
**


** This works just like the Eq opcode except that the jump is taken if
** the operands from the stack are not equal.  See the Eq opcode for
** additional information.
















*/
/* Opcode: Lt P1 P2 P3
**























** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the task is less than the top of the stack.
** See the Eq opcode for additional information.
*/
/* Opcode: Le P1 P2 P3
**

** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the task is less than or equal to the




















** top of the stack.  See the Eq opcode for additional information.
*/
/* Opcode: Gt P1 P2 P3
**






















** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the task is greater than the top of the stack.
** See the Eq opcode for additional information.
*/
/* Opcode: Ge P1 P2 P3
**

** This works just like the Eq opcode except that the jump is taken if
** the 2nd element down on the task is greater than or equal to the




















** top of the stack.  See the Eq opcode for additional information.
*/
case OP_Eq:
case OP_Ne:
case OP_Lt:
case OP_Le:
case OP_Gt:
case OP_Ge: {
................................................................................
  }

  affinity = (pOp->p1>>8)&0xFF;
  if( affinity=='\0' ) affinity = 'n';
  applyAffinity(pNos, affinity);
  applyAffinity(pTos, affinity);

  assert( pOp->p3type==P3_COLLSEQ || pOp->p3==0 );
  res = sqlite3MemCompare(pNos, pTos, (CollSeq*)pOp->p3);
  switch( pOp->opcode ){
    case OP_Eq:    res = res==0;     break;
    case OP_Ne:    res = res!=0;     break;
    case OP_Lt:    res = res<0;      break;
    case OP_Le:    res = res<=0;     break;
    case OP_Gt:    res = res>0;      break;
    default:       res = res>=0;     break;

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.77 2004/05/18 23:21:36 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines
................................................................................
/*
** Allowed values of VdbeOp.p3type
*/
#define P3_NOTUSED    0   /* The P3 parameter is not used */
#define P3_DYNAMIC  (-1)  /* Pointer to a string obtained from sqliteMalloc() */
#define P3_STATIC   (-2)  /* Pointer to a static string */
#define P3_POINTER  (-3)  /* P3 is a pointer to some structure or object */


/*
** The following macro converts a relative address in the p2 field
** of a VdbeOp structure into a negative number so that 
** sqlite3VdbeAddOpList() knows that the address is relative.  Calling
** the macro again restores the address.
*/

*************************************************************************
** Header file for the Virtual DataBase Engine (VDBE)
**
** This header defines the interface to the virtual database engine
** or VDBE.  The VDBE implements an abstract machine that runs a
** simple program to access and modify the underlying database.
**
** $Id: vdbe.h,v 1.78 2004/05/20 13:54:54 drh Exp $
*/
#ifndef _SQLITE_VDBE_H_
#define _SQLITE_VDBE_H_
#include <stdio.h>

/*
** A single VDBE is an opaque structure named "Vdbe".  Only routines
................................................................................
/*
** Allowed values of VdbeOp.p3type
*/
#define P3_NOTUSED    0   /* The P3 parameter is not used */
#define P3_DYNAMIC  (-1)  /* Pointer to a string obtained from sqliteMalloc() */
#define P3_STATIC   (-2)  /* Pointer to a static string */
#define P3_POINTER  (-3)  /* P3 is a pointer to some structure or object */
#define P3_COLLSEQ  (-4)  /* P3 is a pointer to a CollSeq structure */

/*
** The following macro converts a relative address in the p2 field
** of a VdbeOp structure into a negative number so that 
** sqlite3VdbeAddOpList() knows that the address is relative.  Calling
** the macro again restores the address.
*/

u64 sqlite3VdbeSerialType(const Mem *);
int sqlite3VdbeSerialPut(unsigned char *, const Mem *);
int sqlite3VdbeSerialGet(const unsigned char *, u64, Mem *);

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(Cursor*, int , const unsigned char*, int*);
int sqlite3VdbeIdxRowid(BtCursor *, i64 *);
int sqlite3MemCompare(Mem *, Mem *);
int sqlite3VdbeKeyCompare(void*,int,const void*,int, const void*);
int sqlite3VdbeRowCompare(void*,int,const void*,int, const void*);

u64 sqlite3VdbeSerialType(const Mem *);
int sqlite3VdbeSerialPut(unsigned char *, const Mem *);
int sqlite3VdbeSerialGet(const unsigned char *, u64, Mem *);

int sqlite2BtreeKeyCompare(BtCursor *, const void *, int, int, int *);
int sqlite3VdbeIdxKeyCompare(Cursor*, int , const unsigned char*, int*);
int sqlite3VdbeIdxRowid(BtCursor *, i64 *);
int sqlite3MemCompare(const Mem*, const Mem*, const CollSeq*);
int sqlite3VdbeKeyCompare(void*,int,const void*,int, const void*);
int sqlite3VdbeRowCompare(void*,int,const void*,int, const void*);

** negative, zero or positive if pMem1 is less than, equal to, or greater
** than pMem2. Sorting order is NULL's first, followed by numbers (integers
** and reals) sorted numerically, followed by text ordered by memcmp() and
** finally blob's ordered by memcmp().
**
** Two NULL values are considered equal by this function.
*/
int sqlite3MemCompare(Mem *pMem1, Mem *pMem2){
  int rc;

  int combined_flags = pMem1->flags|pMem2->flags; 












 
  /* If one value is NULL, it is less than the other. If both values
  ** are NULL, return 0.
  */
  if( combined_flags&MEM_Null ){
    return (pMem2->flags&MEM_Null) - (pMem1->flags&MEM_Null);
  }

  /* If one value is a number and the other is not, the number is less.
  ** If both are numbers, compare as reals if one is a real, or as integers
  ** if both values are integers.
  */
  if( combined_flags&(MEM_Int|MEM_Real) ){
    i64 diff;
    if( !(pMem1->flags&(MEM_Int|MEM_Real)) ){
      return 1;
    }
    if( !(pMem2->flags&(MEM_Int|MEM_Real)) ){
      return -1;
    }

    if( combined_flags&MEM_Real ){

      if( pMem1->flags&MEM_Int ){

        pMem1->r = pMem1->i;
      }

      if( pMem2->flags&MEM_Int ){

        pMem2->r = pMem2->i;
      }
      if( pMem1->r < pMem2->r ) return -1;
      if( pMem1->r > pMem2->r ) return 1;
      return 0;






    }
    diff = pMem1->i - pMem2->i;
    return diff<0 ? -1 : diff==0 ? 0 : +1;
  }

  rc = (pMem2->flags&MEM_Null) - (pMem1->flags&MEM_Null);
  if( rc ){





    return rc;
  }











  /* Both values must be strings or blobs. If only one is a string, then
  ** that value is less. Otherwise, compare with memcmp(). If memcmp()
  ** returns 0 and one value is longer than the other, then that value
  ** is greater.
  */
  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( rc ){
    return rc;

  }

  return (pMem1->n - pMem2->n);
}

/*
** The following is the comparison function for (non-integer)
** keys in the btrees.  This function returns negative, zero, or
** positive if the first key is less than, equal to, or greater than
** the second.
................................................................................
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    offset1 += sqlite3VdbeSerialGet(&aKey1[offset1], serial_type1, &mem1);
    offset2 += sqlite3VdbeSerialGet(&aKey2[offset2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){
................................................................................
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    offset1 += sqlite3VdbeSerialGet(&aKey1[offset1], serial_type1, &mem1);
    offset2 += sqlite3VdbeSerialGet(&aKey2[offset2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){

** negative, zero or positive if pMem1 is less than, equal to, or greater
** than pMem2. Sorting order is NULL's first, followed by numbers (integers
** and reals) sorted numerically, followed by text ordered by memcmp() and
** finally blob's ordered by memcmp().
**
** Two NULL values are considered equal by this function.
*/
int sqlite3MemCompare(const Mem *pMem1, const Mem *pMem2, const CollSeq *pColl){
  int rc;
  int f1, f2;
  int combined_flags;

  /* Interchange pMem1 and pMem2 if the collating sequence specifies
  ** DESC order.
  */
  if( pColl && pColl->reverseOrder ){
    const Mem *pTemp = pMem1;
    pMem1 = pMem2;
    pMem2 = pTemp;
  }
  f1 = pMem1->flags;
  f2 = pMem2->flags;
  combined_flags = f1|f2;
 
  /* If one value is NULL, it is less than the other. If both values
  ** are NULL, return 0.
  */
  if( combined_flags&MEM_Null ){
    return (f2&MEM_Null) - (f1&MEM_Null);
  }

  /* If one value is a number and the other is not, the number is less.
  ** If both are numbers, compare as reals if one is a real, or as integers
  ** if both values are integers.
  */
  if( combined_flags&(MEM_Int|MEM_Real) ){

    if( !(f1&(MEM_Int|MEM_Real)) ){
      return 1;
    }
    if( !(f2&(MEM_Int|MEM_Real)) ){
      return -1;
    }
    if( (f1 & f2 & MEM_Int)==0 ){
      double r1, r2;
      if( (f1&MEM_Real)==0 ){
        r1 = pMem1->i;
      }else{
        r1 = pMem1->r;
      }
      if( (f2&MEM_Real)==0 ){
        r2 = pMem2->i;
      }else{
        r2 = pMem2->r;
      }
      if( r1<r2 ) return -1;
      if( r1>r2 ) return 1;
      return 0;
    }else{
      assert( f1&MEM_Int );
      assert( f2&MEM_Int );
      if( pMem1->i < pMem2->i ) return -1;
      if( pMem1->i > pMem2->i ) return 1;
      return 0;
    }


  }



  /* If one value is a string and the other is a blob, the string is less.
  ** If both are strings, compare using the collating functions.
  */
  if( combined_flags&MEM_Str ){
    if( (f1 & MEM_Str)==0 ){
      return 1;
    }
    if( (f2 & MEM_Str)==0 ){
      return -1;
    }
    if( pColl && pColl->xCmp ){
      return pColl->xCmp(pColl->pUser, pMem1->n, pMem1->z, pMem2->n, pMem2->z);
    }else{
      /* If no collating sequence is defined, fall through into the
      ** blob case below and use memcmp() for the comparison. */
    }
  }
 
  /* Both values must be blobs.  Compare using memcmp().



  */
  rc = memcmp(pMem1->z, pMem2->z, (pMem1->n>pMem2->n)?pMem2->n:pMem1->n);
  if( rc==0 ){

    rc = pMem1->n - pMem2->n;
  }

  return rc;
}

/*
** The following is the comparison function for (non-integer)
** keys in the btrees.  This function returns negative, zero, or
** positive if the first key is less than, equal to, or greater than
** the second.
................................................................................
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    offset1 += sqlite3VdbeSerialGet(&aKey1[offset1], serial_type1, &mem1);
    offset2 += sqlite3VdbeSerialGet(&aKey2[offset2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2, 0);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){
................................................................................
    ** data to go with the serial type just read. This assert may fail if
    ** the file is corrupted.  Then read the value from each key into mem1
    ** and mem2 respectively.
    */
    offset1 += sqlite3VdbeSerialGet(&aKey1[offset1], serial_type1, &mem1);
    offset2 += sqlite3VdbeSerialGet(&aKey2[offset2], serial_type2, &mem2);

    rc = sqlite3MemCompare(&mem1, &mem2, 0);
    if( mem1.flags&MEM_Dyn ){
      sqliteFree(mem1.z);
    }
    if( mem2.flags&MEM_Dyn ){
      sqliteFree(mem2.z);
    }
    if( rc!=0 ){