Using of `simplify_prefilter` parameter in PostGis datasource

[DDmit04]

Using of `simplify_prefilter` parameter in PostGis datasource

[artemp]

@DDmit04 - you're right, it's not used. Looks like it sneaked while porting
https://github.com/CartoDB/mapnik/blob/f81bdec0f266f0b90b642576033f2c6e2baa2467/plugins/input/postgis/postgis_datasource.cpp

I'm going to remove this parameter, thanks.

PS. As far as I can see, it was used to control usage of ST_SnapToGrid which is currently has following logic

if (simplify_geometries_ && simplify_snap_ratio_ > 0.0)
{
    s<< "ST_SnapToGrid(";
}

[DDmit04]

Thanks for the answer

[DDmit04]

All I found in older versions is

* `simplify_prefilter`: If non-zero, runs a distance filter on geometries to ensure all 
points are at least a certain distance apart. 
Expressed as a proportion of the current pixel size. 
(default: 0.0, feature is OFF) (recommended: 0.5)

It's still relevant?