When faced with a problem you do not understand, do any part of it you do understand, then look at it again
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| — | Grady Booch (citing Heinlein) |
An underlying problem with artificial intelligence that I have personally experience in my forty years in this area is that as soon as an AI technique works, it’s no longer considered AI and is spun off as its own field (for example, character recognition, speech recognition, machine vision, robotics, data mining, medical informatics, automated investing.)
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| — | Ray Kurzweil |
Inside every large, complex program is a small, elegant program that does the same thing, correctly.
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| — | John Graham-Cumming in Some things I’ve learnt about programming |
On database indices efficiency
While researching why SELECT COUNT(*) is slow on PostgreSQL, i found this nice rule-of-thumb for B-tree (the most common type of database index) efficiency:
10% selectivity is the minimum selectivity necessary for a b-tree index to be helpful.
Where selectivity = unique index values / total number records
