ALL POSTS

MySQL GROUP BY and DISTINCT Oddity

At the end of my last MySQL post I mentioned strange behavior with GROUP BY and DISTINCT. This MySQL “feature” could save some resources on sorts and aggregates but generally I would avoid it as this is not portable solution. Generally speaking, query output is non-deterministic — it depends on the full table scan implementation and on the physical order of rows in a table. This means that it’s actually a bug and , instead, MySQL should produce and error on those statements.

ORA-07202: sltln: invalid parameter to sltln

I’ve started to use DBCA more and I try to use its template management capabilities. It looks like templates is not the most robust feature of Database Configuration Assistant. Sometimes, there are issues when I want to reuse template. I reviewed the parameters and found that control_files is set to an empty string. Checked Metaclick and, indeed, this error is related to empty control_files parameter.

Scaling MySpace: Treading Water in a Tsunami

Those of you that that enjoyed my post on Stability, Agility, Scalability and Cost: The eBay example are sure to like this technical interview of the desperate efforts to stay only a bit behind the traffic demands at MySpace, written by David Carr at Baseline Magazine. A worthy read for those of you interested in the lofty heights of database scaling, where we pack oxygen and have to make some choices and compromises along the way.

Slow rman Backups? Check This Out

If you have found rman backups slow in Oracle 10.2.0.2, you should check out note 375386.1 on metalink. It seems the CBO isn’t all its made out to be, and you have to force rman to use the RULE hint instead to make your rman backup run faster

Calling Definer-Rights Procedure as SYSDBA – Security Hole?

In one of my previous posts I mentioned SYSTEM_PRIVILEGE_MAP view. Taking this thread further, I looked into another nice view – V$ENABLEDPRIVS – showing the privileges enabled for the session at the moment. It should be pretty useful if you decide to add some diagnostics into your application. You might also find it very helpful to call from PL/SQL.

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