[Qgis-developer] Server side simplification for Oracle provide - patch to test

[kimaidou]

Hi devs,

I have opened an issue concerning pre-rendering server-side simplification
for Oracle provider:
http://hub.qgis.org/issues/12298

Please read and review the proposed patch. Please test it with Oracle data
in different environments.

This is really a first step and will need more work to be considerd as
usefull.

Here is on extracts of my last comment on the issue :


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A patch attached with a first code runnning.

   - I copy/paste what has been done in PostGreSQL provider, but since
   there is no equivalent for the functions used there, I used instead :

   - SDO_UTIL.RECTIFY_GEOMETRY instead of ST_SnapToGrid , with the
   "tolerance" parameters used to snap to grid :
   http://docs.oracle.com/cd/B19306_01/appdev.102/b14255/sdo_util.htm#BJEICGGA
   - SDO_UTIL.SIMPLIFY instead of ST_SimplifyPreserverTopology


   - I have tested it with only one POLYON layer, and got awkward results,
   which seems to be caused by simplification leading to POINT or LINSTRING
   instead of original geometry type. Perhaps the problems lies also in
   incorrect geometries in my dataset. If you have experience using Oracle
   spatial or locator, please help debug this issue


   - I kept the tolerance used for PostGIS :
   mRequest.simplifyMethod().tolerance() * 0.8 There is surely a room for
   improvement here


   - I do not know if the patch is suitable for both Oracle Locator and
   Oracle spatial

Please test the attached diff file and give feedback or advice

NB: This is the first time I work with Oracle. I invite Oracle
Locator/Spatial gurus to participate, since I am a complete newbie here

NB2: You can use the docker/oracle here to set up a test environment :
https://registry.hub.docker.com/u/alexeiled/docker-oracle-xe-11g/

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