sij/mapnik
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Updated OptimizeRenderingWithPostGIS (markdown)

Igor Canadi 2014-07-15 08:17:38 -07:00
parent 6ebcd31b24
commit f13976390d
1 changed files with 1 additions and 1 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
OptimizeRenderingWithPostGIS.md

@ -13,7 +13,7 @@ This page will detail some measures you can take to make sure you're not wasting
## Keep the SQL resultset as small as possible
### Basics
First, you have to understand how the Datasource table parameter works for each Layer. What happens is that Mapnik takes what you have defined in your `<Parameter name="table>...</Parameter>`, and slaps a `SELECT AsBinary("way"),column,names,needed AS geom ` in front of it, and ending with some SQL to limit results to the BBOX used for the map that's rendering. Mapnik will intelligently limit the columns queried for to what's actually needed in the Styles referenced in the Layer.
First, you have to understand how the Datasource table parameter works for each Layer. What happens is that Mapnik takes what you have defined in your `<Parameter name="table>...</Parameter>`, and slaps a `SELECT AsBinary("way") AS geom,column,names,needed` in front of it, and ending with some SQL to limit results to the BBOX used for the map that's rendering. Mapnik will intelligently limit the columns queried for to what's actually needed in the Styles referenced in the Layer.
Often, when making a new layer and not paying much attention to the Datasource, you may be doing: