MS RFC 22a: Feature cache for long running processes and query processing (update)

[Frank Warmerdam]

Daniel Morissette wrote:
> If I understood the RFC correctly, the proposed solution to this problem 
> will be to embed all layers inside a CACHE wrapper layer, correct? So by 
> default all postgis/oracle/sde/etc connections will still suffer from 
> the double-pass query problem unless we add the CACHE layer around them, 
> right? This adds an additional thing that users needs to be aware of in 
> order to tune their app.

Daniel,

I share this concern.  Essentially that we have put the onus
on the user to setup a cache layer to get queries working
at a reasonable speed instead of treating this internally
as I had originally proposed.

> - What does nesting do if the outer layer is not of connection type 
> cache, layerfilter or geomtrans? For instance what happens if I have a 
> layer of type point (shapefile) which contains two nested layers of type 
> point?

I believe nested layers that are not addressed by their parent or some
other layer would never be used for anything, wouldn't show up in
WMS layer lists, etc.

> - With respect to STYLEITEM AUTO the plan is to cache the class objects 
> for each shape? Won't that be expensive for large layers?

I had this concern too, though it isn't clear to me what else could
be done.  I trust we will only pay this class object penalty when
styleitem auto is in effect.

> I feel bad for raising all those issues since you seem to have put quite 
> a bit of hard work on this, and would need to put even more work to 
> implement it. It also seems that everybody else likes the proposal, so 
> hopefully it's just me who's not "getting it"... and in this case please 
> show me the light.  :)

My conservative side feels very much the same.  The complexity frightens
me, and yet I don't want to be too negative after all the effort Tamas
has put in.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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