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04-25-2008, 12:42 AM
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 Spatial data and mysql I have been storing points in mysql without use of the spatial extension. I do not forsee the need to ever store more than points, and am wondering if the spatial extensions would offer any significant advantages. I have looked a bit for tutorials, etc... and have not found much. One feature that I would like is to be able to find all points withen X distance from of point Y, without doing a table scan. Would the spatial index (Rtree) be able to achieve this? Are there any good tutorials (or heaven forbid, books) that anyone can suggest? Should I go hang out with the cool kids that are using postGIS  -- Rob Wultsch wultsch@gmail.com wultsch (aim)      |
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04-29-2008, 08:26 PM
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| Re: Spatial data and mysql I just did a quick look at the documentation on the mysql spatial extension and it seems like over kill for what you are looking for. An easy way to approximate the search for all points a given distance from another is to simply use a bounding box. An index on the X and Y coordinates of the point then will make the search fast. something like this... SELECT * FROM points WHERE x >= minx AND x <= maxx AND y >= miny AND y <= maxy If your data is evenly distributed in the space about 21% of the returned points will be outside the distance you want. You can then use a script to scan the result to find and reject the points you don't want. I do this for a mapping project I have on a web site. I don't have a lot of data so I can't say how well the performance is. Even if you have a huge data set, as long as your result sets weren't too big, this should be pretty fast. If the points you are dealing with are latitude longitude coordinates, I have the formula you need to calculate the distance written in PHP if you want it. Rob Wultsch wrote: > I have been storing points in mysql without use of the spatial > extension. I do not forsee the need to ever store more than points, > and am wondering if the spatial extensions would offer any significant > advantages. I have looked a bit for tutorials, etc... and have not > found much. > > One feature that I would like is to be able to find all points withen > X distance from of point Y, without doing a table scan. Would the > spatial index (Rtree) be able to achieve this? > > Are there any good tutorials (or heaven forbid, books) that anyone can suggest? > > Should I go hang out with the cool kids that are using postGIS > > -- Chris W KE5GIX "Protect your digital freedom and privacy, eliminate DRM, learn more at http://www.defectivebydesign.org/what_is_drm" Ham Radio Repeater Database. http://hrrdb.com |
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04-29-2008, 08:27 PM
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| Re: Spatial data and mysql On Fri, Apr 25, 2008 at 12:27 AM, Chris W <2wsxdr5@cox.net> wrote: > I just did a quick look at the documentation on the mysql spatial extension > and it seems like over kill for what you are looking for. An easy way to > approximate the search for all points a given distance from another is to > simply use a bounding box. An index on the X and Y coordinates of the point > then will make the search fast. something like this... > > SELECT * > FROM points > WHERE x >= minx AND x <= maxx AND y >= miny AND y <= maxy Thank you for your response. While I rather dislike using hacks the above would probably work well enough for my purposes. Unfortunately I do most of my work in a version of MySQL <5.0 (3.23.49) so I don't have access to the index merge optimization so the above would only use one index for me, but that would probably be good enough. One more reason to try to get my sys admin to upgrade... -- Rob Wultsch wultsch@gmail.com wultsch (aim) |
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