RE: SQL Tunning - result of set autot traceonly
- From: "Chitale, Hemant Krishnarao" <Hemant.Chitale@xxxxxx>
- To: <ecandrietta@xxxxxxxxx>
- Date: Tue, 12 Jul 2011 10:34:19 +0800
Firstly, you must understand that you have extracted only part of the
Execution Plan.
An Execution Plan consists of
A) The Operations --- which are presented in a tabular manner
B) Predicate Information for some of the operations -- which shows
which predicates from the query (or transformed query) were applied at
the corresponding operation
1.) oracle ran the query from 4 to 25 or it ran from 25 to 4
Without knowing the execution plan, we can't really see which step was
executed first and which was executed next and so on.
These numbers are operation IDs -- it doesn't necessarily mean that it
the actual execution was in the same sequence as these IDs.
2.) What does it mean : 'access'
That the rows retrieved by applying this predicate. In general, rows
may be accessed via an Index or a FullTableScan
3.) What does it mean : 'filter'
That rows retrieved from the preceding step in the execution plan were
filtered. Rows are filtered to eliminate those that do not meet the
query requirements
4.) Considering that the item 21 is more selective for query, where must
I put it in the statment:
It doesn't matter where you put it. In theory, the optimizer should be
able to optimize or rewrite the query.
Also, remember that, in some/many cases, you might know more than the
optimizer --- the simplest reason being that the table/column/index
statistics last gathered don't reflect the current nature of the data,
or for more complex reasons such as dependencies between columns etc
Hemant K Chitale
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Eriovaldo Andrietta
Sent: Tuesday, July 12, 2011 7:40 AM
To: ORACLE-L
Subject: SQL Tunning - result of set autot traceonly
Hi Friends,
I have the Result from traceonly, as below.
My doubt is:
1.) oracle ran the query from 4 to 25 or it ran from 25 to 4
2.) What does it mean : 'access'
Means that the oracle process went to the disk to retrieve data
?
3.) What does it mean : 'filter'
Means that oracle process performed a filter in the data that
was in memory (cached) ?
4.) Considering that the item 21 is more selective for query, where
must I put it in the statment:
at the begin of the WHERE CLAUSE or
at the eng of the WHERE CLAUSE ?
Predicate Information (identified by operation id):
---------------------------------------------------
4 - access("T1"."NUM_DOCUMENTO"="SPL"."NUM_DOCUMENTO" AND
"SPL"."NUM_ACIONAMENTO"="VW_COL_1")
5 - access("NUM_DOCUMENTO"="T1"."NUM_DOCUMENTO")
9 - filter("T1"."UF"='XX')
10 - access(ROWID=ROWID)
11 - access(ROWID=ROWID)
12 - access(ROWID=ROWID)
13 - access(ROWID=ROWID)
14 - access(ROWID=ROWID)
15 - access("T1"."UF"='RS')
21 - filter("SPL"."STATUS"=2 AND "SPL"."DATA">=TO_DATE(' 2003-12-19
00:00:00', 'syyyy-mm-dd
hh24:mi:ss') AND "SPL"."DATA"<=TO_DATE(' 2011-07-06
00:00:00', 'syyyy-mm-dd hh24:mi:ss'))
23 - access("T1"."NUM_DOCUMENTO"="SC"."NUM_DOCUMENTO"(+))
24 - filter("TC"."N1"='BRT')
25 - access("T1"."NUM_DOCUMENTO"="TC"."NUM_DOCUMENTO")
Regards
Eriovaldo
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