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Re: appropriate database design and query
Posted by: Rick James
Date: January 14, 2009 08:55PM

That's a tough one.

Look at the GIS indexing.

A database can't do much for you other than make a first pass at which images to consider.

Possibly this would be efficient...
   a SMALLINT, -- one of the values (hopefully the most selective)
   b SMALLINT, -- another
   the_rest BLOB,  -- the other 8*5*4*4*4-3

SELECT the_rest FROM foo
WHERE a BETWEEN ?-20 and ?+20
  AND b BETWEEN ?-20 and ?+20
  AND c BETWEEN ?-20 and ?+20

Then parse "the_rest" (a list of the other values) and test them.
The principles for coming up with this ugly approach:
* It will do a range scan based on "a" -- some help
* Then it will further filter by b and c -- still inside the "index"
* Then it fetches the_rest -- alas, random fetches into the data

If the "a" test eliminates 90% of the rows, and "b" eliminates 90% of them, and ditto for c, then you have to munch on only 1/1000 of the rows. This should be manageable.

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Re: appropriate database design and query
January 14, 2009 08:55PM

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