Author: Alex Gorbachev

Yes, More and More and Moore… but Different!

We humans are not able to process large amount of precise data. In any human–readable report, we don’t need more than ten or twenty lines of numbers. Every time we look at processes or data more complex that that, we employ simplifications — graph trends, mind–mapping, aggregations, and so on. How will we make computers process information just as humans do? Perhaps we can find the answer inside ourselves if we figure out how our minds work. We recognize images even though our brain is not capable of processing huge amounts of data in milliseconds.

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MySQL – No Index Used With ORDER BY + LIMIT and DISTINCT

MySQL – No Index Used With ORDER BY + LIMIT and DISTINCT. This is actually a follow up on my previous post. Developers tried to rewrite all statements and even overdid it. As we say in Russia – “teach fool how to pray and he will break his forehead”.

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Oracle 10.2.0.3 Patchset – Known Issues and Bugs

Oracle 10.2.0.3 Patchset – Known Issues and Bugs. Oracle 10.2.0.3 patchset is not functional on Solaris SPARC 64bit platform with datafiles on Veritas VxFS.

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MySQL Can’t Use Index With Uncorrelated IN Subquery

Today is the first time I had to look at MySQL performance. Tiny database as web application back-end was having significant performance issues with spikes of CPU workload. After identifying problematic queries, I found a pile of statements using IN subqueries. I asked around and our MySQL experts assured me that this is one of the minor and not so disturbing issues, in fact. I can’t imagine what those disturbing issue are. I guess Oracle XE does have some advantages over MySQL for small installations.

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Welcome Doug!

Doug Burns is finally here in Ottawa. You must see his smile in the airport – somehow he managed to read my comment and already expected me while I thought it would be surprise.

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Twitter, Pythian Style… also Oracle’s SYSTEM_PRIVILEGE_MAP

To the subject at hand (psst, there will be some technical stuff in the end)… A few days ago I came across Twitter. I liked that idea very much and even tried it for one evening. I don’t think Twitter fits my lifestyle, but I recognized a very familiar concept. Indeed, it reminds me of one feature of our Pythian Support Track. Time for a bit of technical stuff…since we are mostly talking about databases on this blog, here is a view in Oracle I found very useful one day: SYSTEM_PRIVILEGE_MAP.

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“Federated Array of Bricks” – Deja Vu?

StorageMojo keeps producing interesting material. This time it’s about FAB (Federated Array of Bricks). I wonder if this will make the same hype as RAC? Dear Reader, what is your perspective?

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Using RMAN Repository for Database Growth Trend

REPORT SCHEMA is quite handy to get growth rate of your database/datafile/tablespace providing RMAN repository is used. I don’t remember what triggered that thought but I see it in my “to blog” list so here it goes.

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“change tracking state change latch”

In my UKOUG 06 presentation on block change tracking internals I assumed that “change tracking state change latch” is, probably, used by DBWR and CTWR to protect access to a buffer area in shared pool. I wanted to verify it and tried to trace this latch.

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Which Risks Are You Protected From?

I worked on one site for a while and during 2.5 years it didn’t face a single media corruption of Oracle datafiles. But one day, my fellow DBA (who is usually extremely cautious and reviews his actions at least twice) overwrote a controlfile with some crap. Even the fact that controlfiles were on raw devices didn’t prevent this disaster from happening.

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