SQLite

      && pCur->info.nKey==pX->nKey-1 ){
       loc = -1;
    }else if( loc==0 ){
      rc = sqlite3BtreeMovetoUnpacked(pCur, 0, pX->nKey, appendBias, &loc);
      if( rc ) return rc;
    }
  }else if( loc==0 ){
    if( pX->nMem ){
      UnpackedRecord r;
      memset(&r, 0, sizeof(r));
      r.pKeyInfo = pCur->pKeyInfo;
      r.aMem = pX->aMem;
      r.nField = pX->nMem;
      rc = sqlite3BtreeMovetoUnpacked(pCur, &r, 0, appendBias, &loc);
    }else{
    rc = btreeMoveto(pCur, pX->pKey, pX->nKey, appendBias, &loc);
    }
    if( rc ) return rc;
  }
  assert( pCur->eState==CURSOR_VALID || (pCur->eState==CURSOR_INVALID && loc) );

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

** 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.  NULL for indexes */
  struct Mem *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,
                       int bias, int seekResult);
int sqlite3BtreeFirst(BtCursor*, int *pRes);

                         pIndex->nKeyCol); VdbeCoverage(v);
    sqlite3UniqueConstraint(pParse, OE_Abort, pIndex);
  }else{
    addr2 = sqlite3VdbeCurrentAddr(v);
  }
  sqlite3VdbeAddOp3(v, OP_SorterData, iSorter, regRecord, iIdx);
  sqlite3VdbeAddOp3(v, OP_Last, iIdx, 0, -1);
  sqlite3VdbeAddOp2(v, OP_IdxInsert, iIdx, regRecord);
  sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
  sqlite3ReleaseTempReg(pParse, regRecord);
  sqlite3VdbeAddOp2(v, OP_SorterNext, iSorter, addr2); VdbeCoverage(v);
  sqlite3VdbeJumpHere(v, addr1);

  sqlite3VdbeAddOp1(v, OP_Close, iTab);
  sqlite3VdbeAddOp1(v, OP_Close, iIdx);

    }else{
      if( pPk ){
        /* Add the PK key for this row to the temporary table */
        iKey = ++pParse->nMem;
        nKey = 0;   /* Zero tells OP_Found to use a composite key */
        sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, iKey,
            sqlite3IndexAffinityStr(pParse->db, pPk), nPk);
        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEphCur, iKey, iPk, nPk);
      }else{
        /* Add the rowid of the row to be deleted to the RowSet */
        nKey = 1;  /* OP_Seek always uses a single rowid */
        sqlite3VdbeAddOp2(v, OP_RowSetAdd, iRowSet, iKey);
      }
    }
  

              sqlite3VdbeAddOp2(v, OP_MustBeInt, r3,
                                sqlite3VdbeCurrentAddr(v)+2);
              VdbeCoverage(v);
              sqlite3VdbeAddOp3(v, OP_Insert, pExpr->iTable, r2, r3);
            }else{
              sqlite3VdbeAddOp4(v, OP_MakeRecord, r3, 1, r2, &affinity, 1);
              sqlite3ExprCacheAffinityChange(pParse, r3, 1);
              sqlite3VdbeAddOp4Int(v, OP_IdxInsert, pExpr->iTable, r2, r3, 1);
            }
          }
        }
        sqlite3ReleaseTempReg(pParse, r1);
        sqlite3ReleaseTempReg(pParse, r2);
      }
      if( pKeyInfo ){

        idxInsFlags = OPFLAG_USESEEKRESULT;
        sqlite3VdbeAddOp3(v, OP_Last, iDest, 0, -1);
      }
    }
    if( !HasRowid(pSrc) && pDestIdx->idxType==2 ){
      idxInsFlags |= OPFLAG_NCHANGE;
    }
    sqlite3VdbeAddOp2(v, OP_IdxInsert, iDest, regData);
    sqlite3VdbeChangeP5(v, idxInsFlags|OPFLAG_APPEND);
    sqlite3VdbeAddOp2(v, OP_Next, iSrc, addr1+1); VdbeCoverage(v);
    sqlite3VdbeJumpHere(v, addr1);
    sqlite3VdbeAddOp2(v, OP_Close, iSrc, 0);
    sqlite3VdbeAddOp2(v, OP_Close, iDest, 0);
  }
  if( emptySrcTest ) sqlite3VdbeJumpHere(v, emptySrcTest);
  sqlite3ReleaseTempReg(pParse, regRowid);

  Vdbe *v;
  int r1;

  v = pParse->pVdbe;
  r1 = sqlite3GetTempReg(pParse);
  sqlite3VdbeAddOp4Int(v, OP_Found, iTab, addrRepeat, iMem, N); VdbeCoverage(v);
  sqlite3VdbeAddOp3(v, OP_MakeRecord, iMem, N, r1);
  sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iTab, r1, iMem, N);
  sqlite3ReleaseTempReg(pParse, r1);
}

/*
** This routine generates the code for the inside of the inner loop
** of a SELECT.
**

    ** table iParm.
    */
#ifndef SQLITE_OMIT_COMPOUND_SELECT
    case SRT_Union: {
      int r1;
      r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp3(v, OP_MakeRecord, regResult, nResultCol, r1);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regResult, nResultCol);
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

    /* Construct a record from the query result, but instead of
    ** saving that record, use it as a key to delete elements from
    ** the temporary table iParm.

        ** on an ephemeral index. If the current row is already present
        ** in the index, do not write it to the output. If not, add the
        ** current row to the index and proceed with writing it to the
        ** output table as well.  */
        int addr = sqlite3VdbeCurrentAddr(v) + 4;
        sqlite3VdbeAddOp4Int(v, OP_Found, iParm+1, addr, r1, 0);
        VdbeCoverage(v);
        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm+1, r1,regResult,nResultCol);
        assert( pSort==0 );
      }
#endif
      if( pSort ){
        pushOntoSorter(pParse, pSort, p, r1+nPrefixReg,regResult,1,nPrefixReg);
      }else{
        int r2 = sqlite3GetTempReg(pParse);

            pParse, pSort, p, regResult, regResult, nResultCol, nPrefixReg);
      }else{
        int r1 = sqlite3GetTempReg(pParse);
        assert( sqlite3Strlen30(pDest->zAffSdst)==nResultCol );
        sqlite3VdbeAddOp4(v, OP_MakeRecord, regResult, nResultCol, 
            r1, pDest->zAffSdst, nResultCol);
        sqlite3ExprCacheAffinityChange(pParse, regResult, nResultCol);
        sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, regResult, nResultCol);
        sqlite3ReleaseTempReg(pParse, r1);
      }
      break;
    }

    /* If any row exist in the result set, record that fact and abort.
    */

      for(i=0; i<nKey; i++){
        sqlite3VdbeAddOp2(v, OP_SCopy,
                          regResult + pSO->a[i].u.x.iOrderByCol - 1,
                          r2+i);
      }
      sqlite3VdbeAddOp2(v, OP_Sequence, iParm, r2+nKey);
      sqlite3VdbeAddOp3(v, OP_MakeRecord, r2, nKey+2, r1);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, r1, r2, nKey+2);
      if( addrTest ) sqlite3VdbeJumpHere(v, addrTest);
      sqlite3ReleaseTempReg(pParse, r1);
      sqlite3ReleaseTempRange(pParse, r2, nKey+2);
      break;
    }
#endif /* SQLITE_OMIT_CTE */

    }
#ifndef SQLITE_OMIT_SUBQUERY
    case SRT_Set: {
      assert( nColumn==sqlite3Strlen30(pDest->zAffSdst) );
      sqlite3VdbeAddOp4(v, OP_MakeRecord, regRow, nColumn, regRowid,
                        pDest->zAffSdst, nColumn);
      sqlite3ExprCacheAffinityChange(pParse, regRow, nColumn);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iParm, regRowid, regRow, nColumn);
      break;
    }
    case SRT_Mem: {
      /* The LIMIT clause will terminate the loop for us */
      break;
    }
#endif

    case SRT_Set: {
      int r1;
      testcase( pIn->nSdst>1 );
      r1 = sqlite3GetTempReg(pParse);
      sqlite3VdbeAddOp4(v, OP_MakeRecord, pIn->iSdst, pIn->nSdst, 
          r1, pDest->zAffSdst, pIn->nSdst);
      sqlite3ExprCacheAffinityChange(pParse, pIn->iSdst, pIn->nSdst);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, pDest->iSDParm, r1,
                           pIn->iSdst, pIn->nSdst);
      sqlite3ReleaseTempReg(pParse, r1);
      break;
    }

    /* If this is a scalar select that is part of an expression, then
    ** store the results in the appropriate memory cell and break out
    ** of the scan loop.

    if( okOnePass ){
      sqlite3VdbeChangeToNoop(v, addrOpen);
      nKey = nPk;
      regKey = iPk;
    }else{
      sqlite3VdbeAddOp4(v, OP_MakeRecord, iPk, nPk, regKey,
                        sqlite3IndexAffinityStr(db, pPk), nPk);
      sqlite3VdbeAddOp4Int(v, OP_IdxInsert, iEph, regKey, iPk, nPk);
    }
    sqlite3WhereEnd(pWInfo);
  }

  /* Initialize the count of updated rows
  */
  if( (db->flags & SQLITE_CountRows) && !pParse->pTriggerTab ){

    goto jump_to_p2_and_check_for_interrupt;
  }else{
    pC->nullRow = 1;
  }
  goto check_for_interrupt;
}

/* Opcode: IdxInsert P1 P2 P3 P4 P5
** Synopsis: key=r[P2]
**
** Register P2 holds an SQL index key made using the
** MakeRecord instructions.  This opcode writes that key
** into the index P1.  Data for the entry is nil.
**
** If P4 is not zero, the it is the number of values in the unpacked
** key of reg(P2).  In that case, P3 is the index of the first register
** for the unpacked key.  The availability of the unpacked key can sometimes
** be an optimization.
**
** If P5 has the OPFLAG_APPEND bit set, that is a hint to the b-tree layer
** that this insert is likely to be an append.
**
** If P5 has the OPFLAG_NCHANGE bit set, then the change counter is
** incremented by this instruction.  If the OPFLAG_NCHANGE bit is clear,
** then the change counter is unchanged.
**
** If P5 has the OPFLAG_USESEEKRESULT bit set, then the cursor must have
** just done a seek to the spot where the new entry is to be inserted.

  rc = ExpandBlob(pIn2);
  if( rc ) goto abort_due_to_error;
  if( pOp->opcode==OP_SorterInsert ){
    rc = sqlite3VdbeSorterWrite(pC, pIn2);
  }else{
    x.nKey = pIn2->n;
    x.pKey = pIn2->z;
    x.aMem = aMem + pOp->p3;
    x.nMem = (u16)pOp->p4.i;
    rc = sqlite3BtreeInsert(pC->uc.pCursor, &x,
         (pOp->p5 & OPFLAG_APPEND)!=0, 
        ((pOp->p5 & OPFLAG_USESEEKRESULT) ? pC->seekResult : 0)
        );
    assert( pC->deferredMoveto==0 );
    pC->cacheStatus = CACHE_STALE;
  }
  if( rc) goto abort_due_to_error;
  break;

              ** be tested for.  */ 
              if( iSet ){
                jmp1 = sqlite3VdbeAddOp4Int(v, OP_Found, regRowset, 0, r, nPk);
                VdbeCoverage(v);
              }
              if( iSet>=0 ){
                sqlite3VdbeAddOp3(v, OP_MakeRecord, r, nPk, regRowid);
                sqlite3VdbeAddOp4Int(v, OP_IdxInsert, regRowset, regRowid,
                                     r, nPk);
                if( iSet ) sqlite3VdbeChangeP5(v, OPFLAG_USESEEKRESULT);
              }

              /* Release the array of temp registers */
              sqlite3ReleaseTempRange(pParse, r, nPk);
            }
          }