[Loadstone] Database redesign

Ari Moisio arimo at iki.fi
Thu May 8 10:33:08 BST 2008


On Wed, 7 May 2008, Shawn Kirkpatrick wrote:

> The user id might be a problem but not any time soon. Unfortunately every

  Iirc the birthday theorem we'll get 50 % probability to get duplicate 
userids with 256 users (sqrt(2^16)).

> byte added to a point record makes the database that much bigger. No point
> in a last modified field, duplicate checking is done on import.

   And what will happen if there is a point with  almost similar 
coordinates, different description and similar userid and id fields. How 
does LS know witch is correct?

> The checkpoints aren't part of the database. They can reference the database
> on load but that's only to see if the information needs updating. The only
> difference with a list of route points would be that they're in a particular
> order. When this is implemented there probably won't be much difference if
> any between checkpoint format and route point format.

  How could a non-existent point be checked? If i have understood the 
checkpoint list correctly, please correct me if i'm not,  checkpoint list 
is just a list of coordinates and  with new LS version comments. There are 
also point names and some  other data but they appear to be ignored.

  I made following experiment; i checked a number of points around my 
current location. Then i saved those points. After saving i edited the 
checkpoint file by either moving the checkpoints from few centimeters to 
few meters. Onther chekpoints i renamed. LS was closed during the 
editting. Afterwards i loaded the modified checkpoint file:

- Moved checkpoins were not check anymore and there were no references to 
those poins. This means that checkpoint cannot exist without a stored 
point in the database.

- All so far checked points were named with their original names, ie name 
field in the checkpoint file were ignored.

> There will be a point typing system of some kind. We'll have to work out
> what types to implement thoe and how exactly this will work.

  If there is no room for few bytes for adequate userid i afraid there is 
no room for much classification either.

> On Thu, 8 May 2008, arimo at iki.fi wrote:
>> Hi
>>  If the database will berestructured some day i'll suggest following
>> changes:
>> - User id seems to be currently only 16 bit integer. When user base
>> increase there will a risk of duplicate user ids.
>> - There could be a  last modified field in the point data. When importing
>> database  is update only if the imported point is more recent than same
>> point in the database.
>> - There could be a new class of points, route points. These points are
>> sorted list of lat & lon coordinates and a comment. These point have no
>> relation with the point database and could be freely exchanged with other
>> users regardless if they have similar points in their databases. Maybe
>> these routepoints can someday replace current checkpoint system.
>>  - Personally i do not find much use for separate
>> point classification data.
>> - There could be an option to attach a voice  recording to the point. For
>> practical reasons these recordings will not be   included when exporting
>> the database.
>> You can still escape from the Gates of hell: Use Linux!
>> --
>> mr. M01510
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You can still escape from the Gates of hell: Use Linux!
mr. M01510

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