SQLite

** the sequence value.
*/
case OP_SequenceTest: {
  VdbeCursor *pC;
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( isSorter(pC) );
  assert( !pC->movetoUsed );
  if( (pC->ux.seqCount++)==0 ){
    goto jump_to_p2;
  }
  break;
}

/* Opcode: OpenPseudo P1 P2 P3 * *
** Synopsis: P3 columns in r[P2]

        assert( OP_SeekLE==(OP_SeekLT+1) );
        assert( OP_SeekGT==(OP_SeekGE+1) );
        assert( (OP_SeekLT & 0x0001)==(OP_SeekGE & 0x0001) );
        if( (oc & 0x0001)==(OP_SeekLT & 0x0001) ) oc++;
      }
    } 
    rc = sqlite3BtreeMovetoUnpacked(pC->uc.pCursor, 0, (u64)iKey, 0, &res);
    VVA_ONLY( pC->movetoUsed = 1; )
    pC->ux.movetoTarget = iKey;  /* Used by OP_Delete */
    if( rc!=SQLITE_OK ){
      goto abort_due_to_error;
    }
  }else{
    /* For a cursor with the BTREE_SEEK_EQ hint, only the OP_SeekGE and
    ** OP_SeekLE opcodes are allowed, and these must be immediately followed
    ** by an OP_IdxGT or OP_IdxLT opcode, respectively, with the same key.

case OP_Seek: {    /* in2 */
  VdbeCursor *pC;

  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( !pC->isEphemeral );
  assert( pC->uc.pCursor!=0 );
  assert( pC->isTable );
  pC->nullRow = 0;
  pIn2 = &aMem[pOp->p2];
  VVA_ONLY( pC->movetoUsed = 1; )
  pC->ux.movetoTarget = sqlite3VdbeIntValue(pIn2);
  pC->deferredMoveto = 1;
  break;
}
  

/* Opcode: Found P1 P2 P3 P4 *
** Synopsis: key=r[P3@P4]

  assert( pC->eCurType==CURTYPE_BTREE );
  pCrsr = pC->uc.pCursor;
  assert( pCrsr!=0 );
  res = 0;
  iKey = pIn3->u.i;
  rc = sqlite3BtreeMovetoUnpacked(pCrsr, 0, iKey, 0, &res);
  assert( rc==SQLITE_OK || res==0 );
  VVA_ONLY( pC->movetoUsed = 1; )
  pC->ux.movetoTarget = iKey;  /* Used by OP_Delete */
  pC->nullRow = 0;
  pC->cacheStatus = CACHE_STALE;
  pC->deferredMoveto = 0;
  VdbeBranchTaken(res!=0,2);
  pC->seekResult = res;
  if( res!=0 ){
    assert( rc==SQLITE_OK );

** Write the sequence number into register P2.
** The sequence number on the cursor is incremented after this
** instruction.  
*/
case OP_Sequence: {           /* out2 */
  assert( pOp->p1>=0 && pOp->p1<p->nCursor );
  assert( p->apCsr[pOp->p1]!=0 );
  assert( p->apCsr[pOp->p1]->eCurType==CURTYPE_BTREE );
  assert( p->apCsr[pOp->p1]->isEphemeral );
  assert( !p->apCsr[pOp->p1]->movetoUsed );
  pOut = out2Prerelease(p, pOp);
  pOut->u.i = p->apCsr[pOp->p1]->ux.seqCount++;
  break;
}


/* Opcode: NewRowid P1 P2 P3 * *
** Synopsis: r[P2]=rowid
**

  assert( pC!=0 );
  assert( pC->eCurType==CURTYPE_BTREE );
  assert( pC->uc.pCursor!=0 );
  assert( pC->deferredMoveto==0 );

  hasUpdateCallback = db->xUpdateCallback && pOp->p4.z && pC->isTable;
  if( pOp->p5 && hasUpdateCallback ){
    sqlite3BtreeKeySize(pC->uc.pCursor, &pC->ux.movetoTarget);
  }

#ifdef SQLITE_DEBUG
  /* The seek operation that positioned the cursor prior to OP_Delete will
  ** have also set the pC->ux.movetoTarget field to the rowid of the row that
  ** is being deleted */
  if( pOp->p4.z && pC->isTable && pOp->p5==0 ){
    i64 iKey = 0;
    sqlite3BtreeKeySize(pC->uc.pCursor, &iKey);
    assert( pC->ux.movetoTarget==iKey ); 
  }
#endif
 
  rc = sqlite3BtreeDelete(pC->uc.pCursor, pOp->p5);
  pC->cacheStatus = CACHE_STALE;

  /* Invoke the update-hook if required. */
  if( rc==SQLITE_OK && hasUpdateCallback ){
    db->xUpdateCallback(db->pUpdateArg, SQLITE_DELETE,
                        db->aDb[pC->iDb].zName, pOp->p4.z, pC->ux.movetoTarget);
    assert( pC->iDb>=0 );
  }
  if( pOp->p2 & OPFLAG_NCHANGE ) p->nChange++;
  break;
}
/* Opcode: ResetCount * * * * *
**

  pC = p->apCsr[pOp->p1];
  assert( pC!=0 );
  assert( pC->eCurType!=CURTYPE_PSEUDO || pC->nullRow );
  if( pC->nullRow ){
    pOut->flags = MEM_Null;
    break;
  }else if( pC->deferredMoveto ){
    v = pC->ux.movetoTarget;
#ifndef SQLITE_OMIT_VIRTUALTABLE
  }else if( pC->eCurType==CURTYPE_VTAB ){
    assert( pC->uc.pVCur!=0 );
    pVtab = pC->uc.pVCur->pVtab;
    pModule = pVtab->pModule;
    assert( pModule->xRowid );
    rc = pModule->xRowid(pC->uc.pVCur, &v);

**      * A sorter
**      * A virtual table
**      * A one-row "pseudotable" stored in a single register
*/
struct VdbeCursor {
  u8 eCurType;          /* One of the CURTYPE_* values above */
  i8 iDb;               /* Index of cursor database in db->aDb[] (or -1) */



#ifdef SQLITE_DEBUG
  u8 seekOp;            /* Most recent seek operation on this cursor */
  Bool movetoUsed:1;    /* True if ux.movetoTarget has been used */
#endif
  Bool nullRow:1;        /* True if pointing to a row with no data */
  Bool deferredMoveto:1; /* A call to sqlite3BtreeMoveto() is needed */
  Bool isTable:1;        /* True for rowid tables.  False for indexes */
  Bool isEphemeral:1;   /* True for an ephemeral table */
  Bool useRandomRowid:1;/* Generate new record numbers semi-randomly */
  Bool isOrdered:1;     /* True if the underlying table is BTREE_UNORDERED */
  Pgno pgnoRoot;        /* Root page of the open btree cursor */
  int seekResult;       /* Result of previous sqlite3BtreeMoveto() */
  i16 nField;           /* Number of fields in the header */
  u16 nHdrParsed;       /* Number of header fields parsed so far */
  union {
    BtCursor *pCursor;          /* CURTYPE_BTREE.  Btree cursor */
    sqlite3_vtab_cursor *pVCur; /* CURTYPE_VTAB.   Vtab cursor */
    int pseudoTableReg;         /* CURTYPE_PSEUDO. Reg holding content. */
    VdbeSorter *pSorter;        /* CURTYPE_SORTER. Sorter object */
  } uc;
  KeyInfo *pKeyInfo;    /* Info about index keys needed by index cursors */
  union {
    i64 seqCount;         /* Sequence counter.  Only valid if movetoUsed==0 */
    i64 movetoTarget;     /* Rowid moved to. */
  } ux;
#ifdef SQLITE_ENABLE_COLUMN_USED_MASK
  u64 maskUsed;         /* Mask of columns used by this cursor */
#endif

  /* Cached information about the header for the data record that the
  ** cursor is currently pointing to.  Only valid if cacheStatus matches
  ** Vdbe.cacheCtr.  Vdbe.cacheCtr will never take on the value of

  int res, rc;
#ifdef SQLITE_TEST
  extern int sqlite3_search_count;
#endif
  assert( p->deferredMoveto );
  assert( p->isTable );
  assert( p->eCurType==CURTYPE_BTREE );
  assert( !p->isEphemeral );
  assert( p->movetoUsed );
  rc = sqlite3BtreeMovetoUnpacked(p->uc.pCursor, 0, p->ux.movetoTarget, 0,&res);
  if( rc ) return rc;
  if( res!=0 ) return SQLITE_CORRUPT_BKPT;
#ifdef SQLITE_TEST
  sqlite3_search_count++;
#endif
  p->deferredMoveto = 0;
  p->cacheStatus = CACHE_STALE;