[postgis-users] Storage efficiency of point and line data

[Michael Graff]

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It seems there is a large overhead to storing point and line data in
a geometry type.  mem_size() returns 172 bytes for a two-point line,
and goes up by 24 bytes per additional point.  Returning the data in
binary form seems to show only 6 bytes per point, so perhaps this
is twice the actual storage.

I thought about storing only the bounding boxes in a table, and
storing the actual shape in a flat binary file (probably storing
each lat/long pair as a pair of 32-bit signed integers) but it
turns out that wouldn't be a huge win, as most of the data I have
consists of 2 points:

   cnt    | points | size  
- ----------+--------+-------
 23333966 |      2 |   172
  6789516 |      3 |   196
  3712433 |      4 |   220
  2438493 |      5 |   244
  1749440 |      6 |   268
  1346119 |      7 |   292
   976198 |      8 |   316
   806865 |      9 |   340
   658199 |     10 |   364

Is the storage format fairly efficient, and I'm simply storing a whole
lot of data?

- --Michael
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