RE: views on views on views

From: <>
Date: Fri, 27 Mar 2009 12:17:51 -0400
Message-ID: <>

Yes what a good way to end reading 44 messages. A lively discussion with a worthwhile ending.

Joel Patterson
Database Administrator
904 727-2546
-----Original Message-----
[] On Behalf Of Tanel Poder Sent: Friday, March 27, 2009 11:03 AM
Subject: RE: views on views on views

Here's a little technical detail I've found very useful with Oracle 10.2 when troubleshooting bad plans through views on views on views.

In 10.2 you can set _dump_qbc_tree=1 and hard parse the query against the
view. This will dump you the parsed query block tree into tracefile - with
objects resolved all the way to the base tables (so you'll *see* through the
views easily, without needing to manually parse this stuff in your head).

So if you do this:

SQL> create view myview as select * from all_users;

View created.

And query this:

SQL> select count(*) from myview;



The _dump_qbc_tree gives you following "SQL" against base tables:

  • ACTION NAME:() 2007-09-16 12:19:57.500
  • MODULE NAME:(SQL*Plus) 2007-09-16 12:19:57.500
  • SERVICE NAME:(SYS$USERS) 2007-09-16 12:19:57.500
  • SESSION ID:(146.1984) 2007-09-16 12:19:57.500 QCSDMP: ------------------------------------------------------- QCSDMP: SELECT: (qbc=2B8D1C28) QCSDMP: . (COUNT(*)) (opntyp=2 opndty=0) QCSDMP: FROM: QCSDMP: .MYVIEW QCSDMP: VQB: QCSDMP: SELECT: (qbc=2B8D163C) QCSDMP: .USERNAME QCSDMP: FROM: QCSDMP: .ALL_USERS QCSDMP: VQB: QCSDMP: SELECT: (qbc=2B8CAF78) QCSDMP: U.NAME (USERNAME) QCSDMP: FROM: QCSDMP: SYS.TS$ (TTS) QCSDMP: SYS.TS$ (DTS) QCSDMP: SYS.USER$ (U)
This has been quite useful time-saver, especially in cases where I've never
seen the database/schema before...

I once wrote an article about it too: mn-n

Tanel Poder
Oracle Certified Master
Oracle ACE Director
OakTable Network Member


Received on Fri Mar 27 2009 - 11:17:51 CDT

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