Collection iterator pickler fetch appears in the execution plan

Collection iterator pickler fetch appears in the execution plan

Today, when I used explain plan for to view the SQL Execution plan, the following strange execution plan appeared:

1. SQL> explain plan for select * from test where object_id = 100;
   
3. Explained.
5. SQL> select * from table (dbms_xplan.display ());
7. 14 rows selected.
10. Execution Plan
11. ----------------------------------------------------------
12. Plan hash value: 2137789089
14. Bytes ---------------------------------------------------------------------------------------------
15. | Id | Operation | Name | Rows | Bytes | Cost (% CPU) | Time |
16. Bytes ---------------------------------------------------------------------------------------------
17. | 0 | select statement | 8168 | 16336 | 29 (0) | 00:00:01 |
18. | 1 | collection iterator pickler fetch | DISPLAY | 8168 | 16336 | 29 (0) | 00:00:01 |
19. Bytes ---------------------------------------------------------------------------------------------
22. Statistics
23. ----------------------------------------------------------
24. 14 recursive CILS
25. 12 db block gets
26. 55 consistent gets
27. 0 physical reads
28. 0 redo size
29. 1414 bytes sent via SQL * Net to client
30. 519 bytes encoded ed via SQL * Net from client
31. 2 SQL * Net roundtrips to/from client
32. 1 sorts (memory)
33. 0 sorts (disk)
34. 14 rows processed

After investigation, it is found that the set autotrace on is executed before the use of the explain plan for. After autotrace is disabled, the execution plan is displayed as normal, with a little knowledge and record for reference.