SQLite

};

/*
** Allowed values of UnpackedRecord.flags
*/
#define UNPACKED_NEED_FREE     0x0001  /* Memory is from sqlite3Malloc() */
#define UNPACKED_NEED_DESTROY  0x0002  /* apMem[]s should all be destroyed */
#define UNPACKED_IGNORE_ROWID  0x0004  /* Ignore trailing rowid on key1 */
#define UNPACKED_INCRKEY       0x0008  /* Make this key an epsilon larger */
#define UNPACKED_PREFIX_MATCH  0x0010  /* A prefix match is considered OK */
#define UNPACKED_PREFIX_SEARCH 0x0020  /* A prefix match is considered OK */

/*
** Each SQL index is represented in memory by an
** instance of the following structure.

** Key1 and Key2 do not have to contain the same number of fields.
** The key with fewer fields is usually compares less than the 
** longer key.  However if the UNPACKED_INCRKEY flags in pPKey2 is set
** and the common prefixes are equal, then key1 is less than key2.
** Or if the UNPACKED_MATCH_PREFIX flag is set and the prefixes are
** equal, then the keys are considered to be equal and
** the parts beyond the common prefix are ignored.
**
** If the UNPACKED_IGNORE_ROWID flag is set, then the last byte of
** the header of pKey1 is ignored.  It is assumed that pKey1 is
** an index key, and thus ends with a rowid value.  The last byte
** of the header will therefore be the serial type of the rowid:
** one of 1, 2, 3, 4, 5, 6, 8, or 9 - the integer serial types.
** The serial type of the final rowid will always be a single byte.
** By ignoring this last byte of the header, we force the comparison
** to ignore the rowid at the end of key1.
*/
int sqlite3VdbeRecordCompare(
  int nKey1, const void *pKey1, /* Left key */
  UnpackedRecord *pPKey2        /* Right key */
){
  int d1;            /* Offset into aKey[] of next data element */
  u32 idx1;          /* Offset into aKey[] of next header element */

  ** impact, since this routine is a very high runner.  And so, we choose
  ** to ignore the compiler warnings and leave this variable uninitialized.
  */
  /*  mem1.u.i = 0;  // not needed, here to silence compiler warning */
  
  idx1 = getVarint32(aKey1, szHdr1);
  d1 = szHdr1;
  if( pPKey2->flags & UNPACKED_IGNORE_ROWID ){
    szHdr1--;
  }
  nField = pKeyInfo->nField;
  while( idx1<szHdr1 && i<pPKey2->nField ){
    u32 serial_type1;

    /* Read the serial types for the next element in each key. */
    idx1 += getVarint32( aKey1+idx1, serial_type1 );
    if( d1>=nKey1 && sqlite3VdbeSerialTypeLen(serial_type1)>0 ) break;