RFC 33: Removing msLayerWhichItems()...

Daniel Morissette dmorissette at MAPGEARS.COM
Tue Jul 10 13:47:00 EDT 2007

Steve Lime wrote:
> Hi all: I tried to put some thoughts down regarding removing msLayerWhichItems() from maplayer.c. This sets us up for feature caching, both using Tamas' nested layers and for single pass query support using the resultCacheMemberObj.
> Please see: http://mapserver.gis.umn.edu/development/rfc/ms-rfc-33

If I got this right, this would mean that we would always read all 
attributes for all shapes in a layer whether we need them or not. This 
could have a peformance impact for rendering layers with a large number 
of attributes.

It seems that only queries need to read all the attributes but when 
rendering there is no reason to read them all unless we are doing 
caching or RFC-22a kind of stuff, right?

Could we not instead just provide a mechanism to skip msLayerWhichItems 
(or ignore its results) when doing a query or caching?

Feel free to tell me to shut up as I may not fully understand the impact 
of what I'm suggesting.

Daniel Morissette

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