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10,000 Hits Already !! January 9, 2008

Posted by Richard Foote in Oracle Blog, Richard's Musings.

I’ve just noticed that the hits counter has just reached 10,000 hits.

I’m quite excited as I actually saw it displaying the 10000, being one of those weird people who would drive around the block a couple of times just to see the mileometer reading in the car reach some “special” number. I screamed with frustration once when I just missed 12345 scroll past, 123456 just seemed such a long way away ….

I must admit I had absolutely no idea how many people would read this Blog when I started it almost a month ago. Starting a Blog was something that was mentioned and suggested to me a few times when I attended and presented at the Unconference at Oracle OpenWorld last year.

Now I must admit, I don’t really know whether 10,000 visits in less than a month, including the Christmas Holidays, is actually a lot or not, but if someone asked me a month ago how long I thought it would take me to reach 10,000 hits, I would have guessed (and hoped somewhat) in 6 months or so. So it’s certainly a lot more hits than I ever thought I would get at this early stage.

So to have generated so much interest, so many comments, there’s over 150 although lots are mine I know 🙂 and so many emails is really really, umm what’s the right word, I guess “nice”.

So thank you all for your interest and involvement !!

If someone can give me a bit of warning just before 20,000 is reached, I would appreciate it !!

Introduction To Linguistic Indexes – Part II January 9, 2008

Posted by Richard Foote in Indexing Tricks, Linguistic Indexes, Oracle Cost Based Optimizer, Oracle Indexes, Performance Tuning.

As previously discussed, Linguistic Indexes can potentially be useful with case-insensitive searches and sorts.

However, they have a number of issues and disadvantages.

The first issue is that once the NLS_COMP parameter is set to ‘LINGUISTIC’ and the NLS_SORT parameter is set to something other than ‘BINARY’, standard binary indexes can no longer be used and are ignored by the CBO. This means one needs to have a very careful and consistent indexing strategy to ensure no SQL statements are compromised while Linguistic related NLS parameters are set. Simple demo highlighting issues with mixing Linguistic and Binary Indexes here.  Note these demos follow those in Introduction To Linguistic Indexes Part I.

The next issue is that Linguistic Indexes are ignored for some types of predicate conditions. MIN, MAX and LIKE can not be used with Linguistic Indexes (although LIKE can now be used with 11g). Simple demo highlighting problems with these predicate conditions here.

Finally, Linguistic Indexes typically use more storage than Binary indexes and so have more associated overheads and costs. The differences in storage is dependent on the charactersets associated with the various indexes. Some examples of differences shown here. Warning: This demo has lots of block dumps !!

Linguistic Indexes are worthy of consideration, but so are the associated costs and disadvantages.