Monthly Archives: July 2019

Reading and analyzing trace file contents using just SQL

Posted on by Posted in 12.2, oracle, trace, troubleshooting Leave a comment

Simple example: tracefiles for the last 5 days:

select fc.* 
from v$diag_trace_file f
     join v$diag_trace_file_contents fc
          on f.adr_home=fc.adr_home
          and f.trace_filename=fc.trace_filename
where f.modify_time >= systimestamp - interval'5' minute
  and fc.timestamp  >= systimestamp - interval'5' minute
  and fc.component_name = 'SQL_Trace'
  --and fc.section_name like 'kests%'
  ;
--or:
select tr.*
  from v$diag_app_trace_file tf,
       v$diag_sql_trace_records tr
 where tf.sql_trace = 'Y'
   and tf.modify_time > systimestamp - interval'5'minute
   and tr.adr_home = tf.adr_home
   and tr.trace_filename = tf.trace_filename
   and tr.timestamp > systimestamp - interval'5'minute;

Laterals: is (+) documented for laterals?

Posted on by Posted in bug, CBO, documentation, oracle Leave a comment

I know this syntax for a long time, since when lateral() was not documented yet, but recently I found a bug: the following query successfully returns 1 row:

with a as (select level a from dual connect by level<10)
    ,b as (select 0 b from dual)
    ,c as (select 0 c from dual)
select
  *
from a,
     lateral(select * from b where a.a=b.b)(+) bb
     --left outer join c on c.c=bb.b
where a=1;

         A          B
---------- ----------
         1

But doesn’t if we uncomment “left join”:

with a as (select level a from dual connect by level<10)
    ,b as (select 0 b from dual)
    ,c as (select 0 c from dual)
select
  *
from a,
     lateral(select * from b where a.a=b.b)(+) bb
     left outer join c on c.c=bb.b
where a=1;

no rows selected

And outer apply works fine:

with a as (select level a from dual connect by level<10)
    ,b as (select 0 b from dual)
    ,c as (select 0 c from dual)
select
  *
from a
     outer apply (select * from b where a.a=b.b) bb
     left outer join c on c.c=bb.b
where a=1;

         A          B          C
---------- ---------- ----------
         1