Re: ALL_SYNONYMS versus USER_SYNONYMS
- From: "David Fitzjarrell" <dmarc-noreply@xxxxxxxxxxxxx> (Redacted sender "oratune@xxxxxxxxx" for DMARC)
- To: "lyallbarbour@xxxxxxxxxxxxxxx" <lyallbarbour@xxxxxxxxxxxxxxx>, "mohamed.houri@xxxxxxxxx" <mohamed.houri@xxxxxxxxx>, ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 12 Sep 2014 08:06:45 -0700
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@xxxxxxxxxxxxxxx> 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@xxxxxxxxx
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
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