Parallel threads and JDBC connection pools can be useful, but should not be used blindly. When handling numerous transactions with small overhead on heavily contended systems, batch processing often provides a better solution.

Look-up tables are an ideal way of testing whether characters are of a particular type, and are commonly used in C for functions such as isupper, isdigit etc. You can also use them for your own custom classification tests.

You're very pleased with yourself: you've created your index, and are feeling supremely confident that your query is now going to run much faster. But something's wrong. The query is still slow, and your index is not being used at all. What's going on?