RE: ALL_SYNONYMS versus USER_SYNONYMS

From: Mark W. Farnham <mwf_at_rsiz.com>
Date: Mon, 15 Sep 2014 13:04:29 -0400
Message-ID: <057e01cfd107$1e17db90$5a4792b0$_at_rsiz.com>

… and regardless of the merits of the use, I’m a bit surprised that predicate didn’t push down to generate an identical plan.  

IF they won’t change, perhaps some form of “outline” or an index could fix this if repairing the poor performance is the goal of the folks writing the checks.  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of David Fitzjarrell (Redacted sender "oratune_at_yahoo.com" for DMARC) Sent: Monday, September 15, 2014 11:03 AM To: dedba_at_tpg.com.au; oracle-l_at_freelists.org Cc: Hemant-K.Chitale_at_sc.com
Subject: Re: ALL_SYNONYMS versus USER_SYNONYMS  

It will but not with the query posted as the WHERE clause restricts the output to only those synonyms owned by user.  

David Fitzjarrell

Principal author, "Oracle Exadata Survival Guide"  

On Monday, September 15, 2014 2:56 AM, De DBA <dedba_at_tpg.com.au> wrote:  

I think that user_synonyms won't list public synonyms, whereas all_synonyms should...

Cheers,
Tony

On 15/09/14 18:39, Chitale, Hemant K wrote:

I have developers who prefer to use the ALL_% views (e.g. ALL_TABLES) even when I tell them to use the USER_% views (USER_TABLES).

Must be something in their prior experiences that “taught” them to use the ALL_% views !  

Hemant K Chitale    

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of David Fitzjarrell Sent: Friday, September 12, 2014 11:07 PM To: lyallbarbour_at_sanfranmail.com; mohamed.houri_at_gmail.com; ORACLE-L Subject: Re: ALL_SYNONYMS versus USER_SYNONYMS  

In the absence of the qualifier "where owner=user" ALL_SYNONYMS can contain more synonyms than USER_SYNONYMS however the queries you post are equivalent. I second Lyall's question of why does the app 'need' to know about synonyms? This should be a configuration step prior to releasing the application to production; there should be no need for such a query to be run.  

It sounds like either the developers are misinformed or, well, arrogant. I would hope it is due to misinformation.  

David Fitzjarrell

Principal author, "Oracle Exadata Survival Guide"  

On Friday, September 12, 2014 4:02 AM, Lyall personal <lyallbarbour_at_sanfranmail.com> wrote:  

You could give your developers the code for those two views. user_synonyms text does what they are doing in the where clause. At least looks like that to me.

Strange query for an "application" to run. Why does the app need to know if synonyms exist?  

Sent from my BlackBerry 10 smartphone.

From: Mohamed Houri

Sent: Friday, September 12, 2014 5:47 AM

To: ORACLE-L

Reply To: mohamed.houri_at_gmail.com

Subject: ALL_SYNONYMS versus USER_SYNONYMS  

Dear list,  

I was tuning an application wide performance issue via an AWR report when I found a SQL consuming a huge number of logical I/O and executed several times. This SQL looks like:

SELECT COUNT(1) FROM DUAL WHERE EXISTS
(SELECT 1 FROM ALL_SYNONYMS WHERE SYNONYM_NAME = :B1 AND OWNER = USER
);  

After a couple of minutes of discussion with developers, they refused to get rid of this part of the code which seems to me useless. Then, in a second tentative, I suggested them to replace the above code with the following one:

SELECT COUNT(1) FROM DUAL WHERE EXISTS
(SELECT 1 FROM USER_SYNONYMS WHERE SYNONYM_NAME = :B1
);  

They refused again saying that it will not give the same results.  

Can someone let me know a situation where this result difference is possible?  

SQL> SELECT count(1) FROM ALL_SYNONYMS where OWNER = USER;  

  COUNT(1)

---

       405  

SQL> SELECT count(1) FROM USER_SYNONYMS;  

  COUNT(1)

---

       405  

Thanks in advance  

-- 

Houri Mohamed 

Oracle DBA-Developer-Performance & Tuning 

Member of Oraworld-team <http://www.oraworld-team.com/> 

Visit My         - Blog <http://www.hourim.wordpress.com/> 

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Received on Mon Sep 15 2014 - 19:04:29 CEST