SQLite

        r.eqSeen = 0;
        rc = sqlite3BtreeMovetoUnpacked(pCur, &r, 0, flags!=0, &loc);
      }else{
        rc = btreeMoveto(pCur, pX->pKey, pX->nKey, flags!=0, &loc);
      }
      if( rc ) return rc;
    }

    /* If the cursor is currently pointing to an entry to be overwritten
    ** and the new content is the same as as the old, then use the
    ** overwrite optimization.
    */
    if( loc==0 ){
      getCellInfo(pCur);
      if( pCur->info.nKey==pX->nKey ){
        BtreePayload x2;
        x2.pData = pX->pKey;
        x2.nData = pX->nKey;
        x2.nZero = 0;
        return btreeOverwriteCell(pCur, &x2);
      }
    }

  }
  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );

  pPage = pCur->pPage;
  assert( pPage->intKey || pX->nKey>=0 );
  assert( pPage->leaf || !pPage->intKey );

#define BTREE_AUXDELETE    0x04  /* not the primary delete operation */
#define BTREE_APPEND       0x08  /* Insert is likely an append */

/* An instance of the BtreePayload object describes the content of a single
** entry in either an index or table btree.
**
** Index btrees (used for indexes and also WITHOUT ROWID tables) contain
** an arbitrary key and no data.  These btrees have pKey,nKey set to the
** key and the pData,nData,nZero fields are uninitialized.  The aMem,nMem
** fields give an array of Mem objects that are a decomposition of the key.
** The nMem field might be zero, indicating that no decomposition is available.
**
** Table btrees (used for rowid tables) contain an integer rowid used as
** the key and passed in the nKey field.  The pKey field is zero.  
** pData,nData hold the content of the new entry.  nZero extra zero bytes
** are appended to the end of the content when constructing the entry.
** The aMem,nMem fields are uninitialized for table btrees.
**
** Field usage summary:
**
**               Table BTrees                   Index Btrees
**
**   pKey        always NULL                    encoded key
**   nKey        the ROWID                      length of pKey
**   pData       data                           not used
**   aMem        not used                       decomposed key value
**   nMem        not used                       entries in aMem
**   nData       length of pData                not used
**   nZero       extra zeros after pData        not used
**
** This object is used to pass information into sqlite3BtreeInsert().  The
** same information used to be passed as five separate parameters.  But placing
** the information into this object helps to keep the interface more 
** organized and understandable, and it also helps the resulting code to
** run a little faster by using fewer registers for parameter passing.
*/
struct BtreePayload {
  const void *pKey;       /* Key content for indexes.  NULL for tables */
  sqlite3_int64 nKey;     /* Size of pKey for indexes.  PRIMARY KEY for tabs */
  const void *pData;      /* Data for tables. */
  sqlite3_value *aMem;    /* First of nMem value in the unpacked pKey */
  u16 nMem;               /* Number of aMem[] value.  Might be zero */
  int nData;              /* Size of pData.  0 if none. */
  int nZero;              /* Extra zero data appended after pData,nData */
};

int sqlite3BtreeInsert(BtCursor*, const BtreePayload *pPayload,