Hi,
About crazy talks, what our hardcore Oracle developers do first when they face
problems with efficiency is to start writing some PL/SQL procedures which they
then tune until they are satisfied (of when we say that we have paid enough).
Unfortunately Geoserver can't utilize those fancy creatures at the moment. It
feels to me that they belong logically to the same category than the stored
queries in WFS 2.0 so perhaps Geoserver could support them someday.
-Jukka Rahkonen-
________________________________
Martin Davis wrote:
Now who's talking crazy! :)
+0 on using a full templating language. Seems perhaps a bit of overkill for
the immediate need? The "macro language" already discussed would suffice for
the immediate need I think?
Whatever the syntax used, it seems like the solution has to:
- allow altering the geometry column expression based on whether the context is
a WMS rendering request or something else (data request, preliminary scan for
query schema, etc)
- avoid adding an extra spatial filter if one is already provided (or
alternatively, add it in such a way that the DB doesn't squawk)
To take another slant on this, I realized that the source of the problem is
that for SQL views the "custom SQL" is wrapped in parens before the WMS bbox
filter condition is appended to it. This is what's causing the DB to complain
that the geometry column expression doesn't have an index. If there was a way
to avoid using the parens that would solve the problem nicely (there would be
no need for any macros in the user-supplied SQL, they could use any expression
around the GEOMETRY column (renaming it to GEOMETRY) and they wouldn't have to
supply their own bbox filter condition. One issue is deciding how to append
the bbox condition - it would be necessary to know whether or not a WHERE
clause was already present. This could perhaps be determined by a flag
supplied by the user.
On Wed, Mar 11, 2015 at 9:22 PM, Andrea Aime
<andrea.a...@geo-solutions.it<mailto:andrea.a...@geo-solutions.it>> wrote:
On Thu, Mar 12, 2015 at 1:15 AM, Martin Davis
<mtncl...@gmail.com<mailto:mtncl...@gmail.com>> wrote:
Uuuh... the result might become very confusing... in the simple case you might
want to just change a function call,
in the complex one you might have to rewrite half of the query.
Well, let's not let the best be the enemy of the good. I'd be happy if the
"simple" case was handled.
So I've been talking about this with Jody, and he's been pretty horrified about
what I proposed, but
here it goes anyways: it seems to me that what you are looking for is some sort
of templating language
to write a query.
Right now parametric queries are sort of our templating language, but to do
what you want you
need control structures that would emit different sql bits depending on the
zoom level... so
it seems to me that what you want is a freemarker template for sqlviews... and
it would be up
to you to make sure that whatever you write always returns the same
_structure_, the same
attribute names and types.
There are of course ugly sides to this:
* We'd need to add a relatively large dependency to gt-jdbc (freemarker, if we
care for consistency
with what is alread in use in GeoServer) since the sql expansion is done
there
* We'd need to start passing in a set of "well known" variables to it, bbox,
current zoom level, target
pixel size, and so on
* Checking that the template would not result in something easy to attack with
sql injection would
be hard
But it seems it would satisfy all your needs, and more
Cheers
Andrea
--
==
GeoServer Professional Services from the experts! Visit
http://goo.gl/NWWaa2 for more information.
==
Ing. Andrea Aime
@geowolf
Technical Lead
GeoSolutions S.A.S.
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313<tel:%2B39%200584%20962313>
fax: +39 0584 1660272<tel:%2B39%200584%201660272>
mob: +39 339 8844549<tel:%2B39%20%C2%A0339%208844549>
http://www.geo-solutions.it
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