[mapserver-dev] incorrect layer drawing order issue

geographika geographika at gmail.com
Fri Nov 7 02:24:33 PST 2014

Hi list,

I have come across an issue that is critical to the project I am working 
on and wondered if it applies to all database drivers or just the SQL 
Server 2008 one.

I have logged the issue on GitHub at: 

I will try some tests over the weekend to see if the Postgres driver 
works the same way, but there seems to be no way of guaranteeing feature 
display order - even if all documentation suggests it can be achieved in 
a database layer using "ORDER BY"
Whilst for a low number of records the order seems ordered, with 150+ 
features I get different images returned each time by my WMS service. No 
use of clustered indexes, partition statements etc. can get around this 
as SQL result sets can only be guaranteed with an ORDER BY in the 
outermost statement.

I note that in http://mapserver.org/fr/development/rfc/ms-rfc-105.html 
there is a new function msLayerBuildSQLOrderBy() that allows sorting to 
be done outside of the layer's DATA statement for WFS requests with a 
SORTBY parameter. Maybe this could also be used by a new LAYER "SORT" 
config keyword?

I see the above is only implemented for a few drivers. The client would 
be willing to fund adding this to the SQL Server driver if there are any 
core devs interested in doing this.



twitter: @geographika

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