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Jim Gray Is Missing
K-Man writes "Jim Gray, Turing Award winner and developer of many fundamental database technologies, was reported missing at sea after a short solo sailing trip to the Farallon Islands off San Francisco. Gray is manager of Microsoft's eScience group. The Coast Guard is searching for his vessel over 4,000 square miles of ocean, and there have been no distress calls or signals of any kind. Gray is 63 and a sailor with 10 years' experience."
The dangers of knowledge trigger emotional distress in human beings.
If he was going offshore, he either had or should have had an EPIRB (Emergency Position Indicating Radio Beacon. In effect, when deployed they transmit a beacon signal at 406MHz that contains a unique identifier, and can also include GPS coordinates.
These signals are picked up by either the INMARSAT geostationary satellites, or also passing weather satellites. Without a GPS position, the weather satellites can locate the beacon to within about 50 miles. With an integrated GPS receiver, the position will be reported to about 2 miles or so. (The message format doesn't have the space to transmit full resolution).
...si hoc legere nimium eruditionis habes...
This story covers some of his recent database work.
Several news stories say that he called his daughter Sunday morning to say he was going out of cellphone range, but he didn't indicate any problems. The weather was clear, so it's puzzling that there were no sightings.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
He went out in a 40-foot C&C 121 yacht. That's a very nice boat, with a epoxy resin laminate hull, carbon fiber reinforcement and masts, Kevlar sails, and a 38HP engine. There hasn't been any weather lately bad enough to give a boat like that any serious trouble. If it ran aground it would probably survive the experience.
But between San Francisco and the Farralon Islands is a major shipping lane. One with fog. Container ships and oil tankers come through there. Sizable fishing boats have been run down and sunk without anyone on a large ship even noticing. There's a USGS Vessel Traffic Service station and established traffic lanes for large ships, but small boats aren't required to check in with traffic control.
An example would be if you have an address book, listing about 50 people you know, with names and addresses (But no phone numbers)
You also have a phone book, with names and phone numbers of everyone in your city. Let's say 1 million people.
Let's say you've got an address ("12 Pear Tree"), and you want a phone number. To find this information you've got to use the address book to locate the name of the person living at that address, then look up that name in the phone book.
In SQL, you'd do that search like this: It's saying "Find every address entry where the address is "12 pear tree", and out of all the possible combinations of address book entry and phone book entry, just give me the ones where the names match."
That'll give you the result you want. However, it's that last bit of SQL that's easy to forget, the "phone_book.name=address_book.name" bit. Without it, you're doing a Cartesian join. The database says "Ahh, they must want every combination of these two tables".
So instead of getting one result, you'll get one million results. The address has to be "12 pear tree", but the database is free to match that up with EVERY entry in the phone book, and it will.
That's what the grandparent post was referring to. SQL just makes that mistake very easy to make, and you'll end up with a GIANT pile of results flying at you if you make it.
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