[postgis-devel] PostGIS 3 thought experiment

Nicklas Avén nicklas.aven at jordogskog.no
Wed Jan 17 11:35:24 PST 2018


Always nice to get visions of the future :-)

I would like to see functions get precision/tolerance aware.
If users are aware of the accuracy of their data set they have no need
to store the data with full double precision. 

So I would like to see the possibility to store data natively in
PostGIS in something similar to TWKB, and then use the data in
functions that can handle the reduced precision. So if I have a data
set with accuracy of 1 cm, I store it with 2 decimals and get 2
decimals back from area calculations.

And a point on my 2 decimal line will intersect if it is closer than 1
cm from the line

and so on.

BTW, what is "Modern C"


On Wed, 2018-01-17 at 09:44 -0800, Paul Ramsey wrote:
> What else is on everyone's wish list? Preferably things you'd do if
> you didn't think everyone would shoot you down for being too
> disruptive.
> https://trac.osgeo.org/postgis/wiki/PostGIS3
> * Break out a postgis_raster extension with a postgis dependency, so
> raster support becomes optional.
> * Require installation in a 'postgis' schema, always and for ever
> * Yet another serialization, this time changing to use external
> storage type, and adding our own compression scheme for coordinates.
>   * An uncompressed header, so header info can always be efficiently
> "sliced" and read, even for very large objects
>   * A hash key for use in fast and small equality comparisons (for
> use
> in cached comparison code)
>   * A compression format optimized for doubles
>   * Other compression formats with other tradeoffs (?) like TWKB for
> higher ratio with precision loss
>   * Implies indirection in coordinate access again: smaller, more
> efficient must be balanced against direct access to coordinates
> * Move up to "modern" C and use whatever cool features we like from
> that
> * Modern GEOS version requirement?
> * Some major GEOS surgery to allow memory management by palloc?
> * Some major GEOS surgery to build coordinateSequence directly on top
> of PostGIS pointlists?
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