how to interpret dbms_xplan.display

From: Ed Wong <ewong_at_mail.com>
Date: 10 May 2004 15:58:57 -0700
Message-ID: <a5ae1554.0405101458.23690268@posting.google.com>

I am using dbms_xplan.display to generate explain on a 9.2 database(see below). Just wondering what is what is the unit of the last column "Cost" and "%CPU"? And why is the "Rows" show 12M where an index is being used? Thanks.

SQL> explain plan for select * from seq where id = 1000000; Explained.

SQL> select * from table(dbms_xplan.display);

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| Id  | Operation                   |  Name       | Rows  | Bytes |

Cost (%CPU)|

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| 0 | SELECT STATEMENT | | 1 | 695 |  4 (25)|
| 1 | TABLE ACCESS BY INDEX ROWID| SEQ | 1 | 695 |  4 (25)|
|* 2 | INDEX UNIQUE SCAN | PK_SEQ | 12M| |  3 (34)|

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Predicate Information (identified by operation id):

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   2 - access("SEQ"."ID"=1000000) Received on Mon May 10 2004 - 17:58:57 CDT