Re: Re: Explain Plan and Security

If I followed this thread right, there is nothing you can do than execute the query. Everything else will generate different results. Is there any chance you get permission to execute the query if you can guarantee it only runs for "a very short time"? E.g. a special (proxy) user with a very strict LOGICAL_READS_PER_SESSION comes to my mind.
Or you add an additional filter with "where 1 =impossible_function" and your "impossible_function" does an execute immediate "select 1/0 from dual". More methods come to my mind, but I'm sure you get the idea. The execution-trap can be tested in non-profit environment and so you might convince your customer?

hth,
 berx

l.flatz_at_bluewin.ch <l.flatz_at_bluewin.ch> schrieb am Fr., 15. Juni 2018, 10:20:

> Thanks to all for discussing.
> Well, actually my case is that we have a sql monitor of a query that went
> wrong. By analyzing the sql monitor result we have a fair idea what kind of
> plan we want.
> From the monitor we also have the exact bind variable values and can
> generate a run script.
> We can then take some action to fix the issue, like recalculation stats,
> rewriting the query somewhat.
> Of course we want to check if our fix works.
> We are not allowed to run the query in production. (The Therefore the next
> best thing would be good execution plan.)
> I tried explain plan, but the bind variables matter and so far I never got
> a good prediction.
>
> It seems to me the whole matter is a bit more complex than I originally
> thought. Therefore I really wan´t to ping the usual suspects.
>
> Regards
>
> Lothar
>
> ----Ursprüngliche Nachricht----
> Von : jonathan_at_jlcomp.demon.co.uk
> Datum : 14/06/2018 - 19:56 (GMT)
> An : oracle-l_at_freelists.org
> Betreff : Re: Explain Plan and Security
>
>
> Dominic,
>
> There's no question that if the query has executed and you can get there
> in time then the plan you get from display_cursor() is the plan that
> actually happened, but we're discussing the point that we can get execution
> plans into memory (for display_cursor()) to report) that have never
> executed - which leafs to the point that those are plans that might never
> actually happen with any real user inputs.
>
> Regards
> Jonathan Lewis
>
>
>
> ________________________________________
> From: Dominic Brooks <dombrooks_at_hotmail.com>
> Sent: 14 June 2018 18:52
> To: Jonathan Lewis
> Cc: oracle-l_at_freelists.org
> Subject: Re: Explain Plan and Security
>
> Well ... dbms_xplan.display_cursor gives you definitively the execution
> plan you just got for your SQL/child. It might not be the plan you get
> every execution under all circumstances but you can’t take away that you
> got that once. You can’t say the same about explain plan.
> If someone is executing a piece of sql, say they are testing / making a
> change, and they want to document the execution plan that they got during
> their test and show that, for one execution at least the plan and
> performance was ok, then dbms_xplan.display_cursor (or getting the same
> info direct from v$sql_plan) is the source for that. That’s what I expect
> developers to provide plus the runtime execution stats.
> Ditto for extracting the plan information for any particular child cursor
> that is in memory, display_cursor tells you what it is/was. No doubts.
>
> Sent from my iPhone
>
> > On 14 Jun 2018, at 18:40, Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
> wrote:
> >
> >
> > Andy,
> >
> > I don't think I'd even be that generous. I can't think of any detail
> where dbms_sql/dbms_xplan.display_cursor() gives you safer information than
> explain plan / dbms_xplan.display().
> > I suppose the extra complexity of using dbms_sql might make you a little
> more careful as you set up a test, and that could be a benefit.
> >
> > Regards
> > Jonathan Lewis
> >
> >
> > ________________________________________
> > From: andyklock_at_gmail.com <andyklock_at_gmail.com> on behalf of Andy Klock
> <andy_at_oracledepot.com>
> > Sent: 14 June 2018 17:15
> > To: Jonathan Lewis
> > Cc: oracle-l_at_freelists.org
> > Subject: Re: Explain Plan and Security
> >
> > Ah! Indeed. Thanks for that Jonathan. So, the takeaway is that DBMS_SQL
> is slightly better than EXPLAIN PLAN. But, only slightly?
> >
> > Thanks!
> >
> > Andy K
> >
> > On Thu, Jun 14, 2018 at 12:08 PM, Jonathan Lewis <
> jonathan_at_jlcomp.demon.co.uk<mailto:jonathan_at_jlcomp.demon.co.uk>> wrote:
> >
> > Andy,
> >
> > If you add a "describe columns" to your SQL PARSE TEST BIND you find
> that you do get a plan before the execute.
> >
> > DECLARE
> > cursor_name INTEGER;
> > rows_processed INTEGER;
> > m_desc_table dbms_sql.desc_tab;
> > m_colcount number;
> >
> > BEGIN
> > cursor_name := dbms_sql.open_cursor;
> > dbms_sql.parse(cursor_name, 'select /* SQL_PARSE TEST BIND */ * from
> parse_test where n = :n', dbms_sql.NATIVE);
> > dbms_sql.bind_variable(cursor_name, ':n', 2);
> > dbms_sql.describe_columns( cursor_name, m_colcount, m_desc_table );
> > END;
> > /
> >
> > SQL> select sql_id, plan_hash_value, sql_text from V$sql where sql_text
> like '%SQL_PARSE TEST BINDwq%'
> > 2 /
> >
> > SQL_ID PLAN_HASH_VALUE
> > ------------- ---------------
> > SQL_TEXT
> >
> ------------------------------------------------------------------------------------------------------------------------------------
> > 911jt1m3dxrba 903671040
> > select sql_id, plan_hash_value, sql_text from V$sql where sql_text like
> '%SQL_PARSE TEST BINDwq%'
> >
> >
> > Regards
> > Jonathan Lewis
> >
> > ________________________________________
> > From: andyklock_at_gmail.com<mailto:andyklock_at_gmail.com> <
> andyklock_at_gmail.com<mailto:andyklock_at_gmail.com>> on behalf of Andy Klock <
> andy_at_oracledepot.com<mailto:andy_at_oracledepot.com>>
> > Sent: 14 June 2018 16:56
> > To: mauro.pagano_at_gmail.com<mailto:mauro.pagano_at_gmail.com>
> > Cc: Jonathan Lewis; oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>;
> l.flatz_at_bluewin.ch<mailto:l.flatz_at_bluewin.ch>
> > Subject: Re: Explain Plan and Security
> >
> > Agreed. It's kind of a cool idea, however, BINDs are checked after the
> DBMS_SQL.PARSE call and is only evaluated after the call to DBMS_SQL.EXECUTE
> >
> >
> https://nam01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.oracle.com%2Fdatabase%2F121%2FARPLS%2Fd_sql.htm%23i996870&data=02%7C01%7C%7C7f3f2e59790c49647afd08d5d21ddcb7%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636645948067016044&sdata=4kyFobAwG5FlvMc2tloVVZpwaeRzJ%2BpMu7JvwWzxJqo%3D&reserved=0
> >
> > I ran a quick test to see what shows up in the cursor cache after
> setting bind_variable, but not calling EXECUTE and as expected you don't
> get a plan at all.
> >
> >
> > SQL> DECLARE
> > cursor_name INTEGER;
> > rows_processed INTEGER;
> > BEGIN
> > cursor_name := dbms_sql.open_cursor;
> > dbms_sql.parse(cursor_name, 'select /* SQL_PARSE TEST */ * from
> parse_test where n = 1', dbms_sql.NATIVE);
> > END;
> > /
> >
> > PL/SQL procedure successfully completed.
> >
> >
> > SQL> DECLARE
> > cursor_name INTEGER;
> > rows_processed INTEGER;
> > BEGIN
> > cursor_name := dbms_sql.open_cursor;
> > dbms_sql.parse(cursor_name, 'select /* SQL_PARSE TEST BIND */ * from
> parse_test where n = :n', dbms_sql.NATIVE);
> > dbms_sql.bind_variable(cursor_name, ':n', 2);
> > END;
> > /
> >
> > PL/SQL procedure successfully completed.
> >
> > SQL> DECLARE
> > cursor_name INTEGER;
> > rows_processed INTEGER;
> > BEGIN
> > cursor_name := dbms_sql.open_cursor;
> > dbms_sql.parse(cursor_name, 'select /* SQL_PARSE TEST BIND 2 */ * from
> parse_test where n = :n', dbms_sql.NATIVE);
> > dbms_sql.bind_variable(cursor_name, ':n', 2);
> > rows_processed := dbms_sql.execute(cursor_name);
> > dbms_sql.close_cursor(cursor_name);
> > END;
> > /
> >
> > PL/SQL procedure successfully completed.
> >
> > SQL> _at_findsq SQL_PARSE
> >
> > SQL_ID PLAN_HASH_VALUE LENGTH(SQL_FULLTEXT) SUB_TEXT
> EXECUTIONS AVG_ELAPSED
> > ------------- --------------- --------------------
> -------------------------------------------------- ---------- -----------
> > 4wbhzrjq0k7fd 464636435 57 select /* SQL_PARSE TEST */ * from
> parse_test wher 0 .002671
> > 8xbgz1hbjk0vz 0 63 select /* SQL_PARSE TEST BIND */ * from
> parse_test 0 .000467
> > 0bavj3vaszvw2 464636435 65 select /* SQL_PARSE TEST BIND 2 */ * from
> parse_te 1 .00503
> >
> > Final note, if you don't actually execute the SQL then you don't get all
> that other Oracle runtime stuff like cardinality feedback or dynamic
> sampling, etc which adds to even more headaches.
> >
> > Andy K
> >
> > On Thu, Jun 14, 2018 at 11:45 AM, Mauro Pagano <mauro.pagano_at_gmail.com
> <mailto:mauro.pagano_at_gmail.com><mailto:mauro.pagano_at_gmail.com<mailto:
> mauro.pagano_at_gmail.com>>> wrote:
> > Lothar,
> >
> > To add on Jonathan's "odd note", because of 9630032 (disabled by
> default) you might see an even odder behavior (difference between describe
> vs exec).
> > Just saying that DBMS_SQL might translate in some headaches :-(
> >
> > Cheers,
> > Mauro
> >
> > On Thu, Jun 14, 2018 at 7:13 AM, Jonathan Lewis <
> jonathan_at_jlcomp.demon.co.uk<mailto:jonathan_at_jlcomp.demon.co.uk><mailto:
> jonathan_at_jlcomp.demon.co.uk<mailto:jonathan_at_jlcomp.demon.co.uk>>> wrote:
> >
> > As far as I know explain plan will produce a misleading plan only if:
> >
> > a) the query uses bind variables - which can't be peeked and are assumed
> to be character
> > or
> > b) the literals used in the explain plan are a bad choice compared to
> what happens in production
> > (which includes wrong type, wrong character set, wrong implicit date
> format etc.)
> >
> > Using dbms_sql won't (necessarily) be any better. If you supply a
> statement with a bind variable in the text the call to dbms_parse will
> assume that it's an unknown varchar - just as explain plan will. This is
> why you sometimes see systems with lots of statements parsed twice per
> execute - the first time was a parse call the that used guesses for bind
> types, the second was with information about the actual bind types.
> >
> > (I have an odd note from 16 years ago that you don't get the plan on the
> call to dbms_parse, but have to call dbms_describe_colums as well).
> >
> > Regards
> > Jonathan Lewis
> >
> > ________________________________________
> > From: oracle-l-bounce_at_freelists.org<mailto:oracle-l-bounce_at_freelists.org
> ><mailto:oracle-l-bounce_at_freelists.org<mailto:
> oracle-l-bounce_at_freelists.org>> <oracle-l-bounce_at_freelists.org<mailto:
> oracle-l-bounce_at_freelists.org><mailto:oracle-l-bounce_at_freelists.org
> <mailto:oracle-l-bounce_at_freelists.org>>> on behalf of l.flatz_at_bluewin.ch
> <mailto:l.flatz_at_bluewin.ch><mailto:l.flatz_at_bluewin.ch<mailto:
> l.flatz_at_bluewin.ch>> <l.flatz_at_bluewin.ch<mailto:l.flatz_at_bluewin.ch
> ><mailto:l.flatz_at_bluewin.ch<mailto:l.flatz_at_bluewin.ch>>>
> > Sent: 14 June 2018 13:36:46
> > To: oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org><mailto:
> oracle-l_at_freelists.org<mailto:oracle-l_at_freelists.org>>
> > Subject: Explain Plan and Security
> >
> > Hi,
> >
> > you might know Kerry´s classic blog:
> https://nam01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fkerryosborne.oracle-guy.com%2F2008%2F10%2Fexplain-plan-lies%2F&data=02%7C01%7C%7C7f3f2e59790c49647afd08d5d21ddcb7%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636645948067016044&sdata=0MfIBWr%2FbqDjJeSA9AMeySqqeQnBo5odXPC8wxYqthY%3D&reserved=0
> .
> > Normally my work around for explain plan issues is to run the query and
> use dbms_xplan.display_cursor.
> > Now I am working in an environment where I must not run a query, but I
> can do explain plan.
> > But still I think I can not tolerate explain plan weaknesses.
> > I think it should be possble to use DBMS_SQL to parse a statement and
> receive a proper plan without actually running the statement.
> > Then use dbms_xplan.display_cursor.
> > Before I spent time, has anybody done it already?
> >
> > Regards
> >
> > Lothar
> >
> > --
> >
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