[OSM-dev] Using NULL values in mapnik / postgres DB

[Artem Pavlenko]

Jon,

Sounds good to me! Also, it might be a good idea to split osm data into 
multiple tables in postgresql and only keep fields that are required :

1. roads (LINESTRING) :  osm_id,highway,level,name ...
2. all points (POINT) : osm_id, amenity,...
3. all polygons (POLYGONS): osm_id, natural, leisure etc.

Thoughts?

Also, I'm not entirely convinced that using TEXT is more efficient than 
VARCHAR(<length>) ???  Was it mentioned somewhere in docs? 

And last one:) . How about correcting geometries at the translation stage? I 
think we can use GEOS (c++ lib) to 'node' and 'linemerge' _bad_ ways into 
clean ones. 

Artem

On Tuesday 20 February 2007 21:40, Jon Burgess wrote:
> I received an email from Martin Spott which suggested that we change the
> Postgres database fields used by osm2pgsql + mapnik to utilise NULL in
> place of empty text strings.
>
> Martin believes this will make the database lookups more efficient and
> i'm inclined to believe him.
>
> To make this change we need to change both osm2pgsql.c and the osm.xml
> mapnik rules to generate and parse the NULL SQL values.
>
> I've done a quick trial on my local machine and it is fairly trivial to
> implement this. For reference the osm.xml changes look like:
>
>   char_length(foo)=0   changes to   foo IS NULL
>   char_length(foo)>0   changes to   foo IS NOT NULL
>
> Any thoughts about whether I should go ahead and make this change?
>
> Jon
>
>
>
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