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May 2010


I’ve just received an email telling me that I’m a linchpin – according to this picture on Seth Godin’s website. Filed under: Uncategorized

Quiz Night

I have two queries designed to return the same result set in the same order. In outline they look like this (look carefully at the from clauses): select ... from tableA t1, tableB t2 where t1.filter = ... and t2.join = t1.join and t2.filter = ... order by ... select ... from tableA t1, tableB [...]

Filter Early

Yesterday, my 12 year-old son Alex was excited to tell me that he had learned a new trick that made it easier to multiply fractions. Here’s the trick:

Missing wait event

Oracle for Windows is out for some time. I’ve installed it on my 32-bit Windows XP machine because I like Windows – just to check that it’s actually working fine. Playing with TPC-H test using Hammerora I’ve noticed an anomaly in the way Oracle reports IO waits for some queries. Here is a test [...]

A blog to watch

I see that Nigel Noble has started blogging. I’ve spent some time at the company where he works, so I know how close he gets to the bleeding edge of Oracle technology – you might want to keep an eye on what he has to say. I’ve added his URL to the list of links [...]

Refreshing a Test Database using exp/imp

I’ve just taken a quick look at the Calendar and it appears to be 2010. However I’m still seeing, and being asked, to refresh a number of test databases using schema mode exports. This can present a challenge because there are a number of database objects that typically aren’t created by a schema mode import. [...]

Concatenated Bitmap Indexes Part II (Everybody’s Got To Learn Sometime)

A basic little post to conclude this discussion. The issues regarding whether to go for single column indexes vs. concatenated indexes are similar for Bitmap indexes as they are for B-Tree indexes.   It’s generally more efficient to access a concatenated index as it’s only the one index with less processing and less throwaway rowids/rows [...]

Philosophy – 10

The most significant question to ask when thinking about adding a new index: “Will the index eliminate significantly more work than it introduces (at the moments when it really matters) ?” A few examples of “moments that matter”: Bulk housekeeping Highly concurrent OLTP activity Frequent high-precision reporting Acceptance testing for side effects [Back to Philosophy [...]

AOUG Conference in Vienna

This is a short note to point out that I just added to the Public Appearances page the next conference organized by the AOUG in Vienna. It will take place on June 15. My talk will be about edition-based redefinition. The full agenda (incl. abstracts) is available here. It is interesting to point out that [...]

A SQLNet thing I probably forgot about...

My most recent "ah-hah", or "oh yeah" moment came reading Jonathan Lewis's blog. A very neat "SQL Net compression" detail.

It is one of those things that I cannot remember if it was something I knew but forgot - or just never knew.

His example makes the point nicely, you have to appreciate those little test scripts for that. You can clearly see what a difference an order by might make on a the size of a result set set across the network.

Yet another reason to look at bulk processing - the more reasons the better...