sqliteBtreeCursor
rc = sqliteBtreeCursor(db->aDb[iDb].pBt, 2, 0, &curMain);
rc = sqliteBtreeCursor(pBt, iTable, wrFlag, &pCur);
rc = sqliteBtreeCursor(pX, p2, wrFlag, &p->aCsr[i].pCursor);
rc = sqliteBtreeCursor(pCx->pBt, pgno, 1, &pCx->pCursor);
rc = sqliteBtreeCursor(pCx->pBt, 2, 1, &pCx->pCursor);