On 01/24/2017 02:27 AM, Andrea Aime wrote:
On Tue, Jan 24, 2017 at 1:28 AM, Dave Blasby <dbla...@boundlessgeo.com
<mailto:dbla...@boundlessgeo.com>> wrote:
For the get capabilities (layer Time dimension set to LIST and
default=max value) you will see two queries;
1. unique visitor (Postgis: SELECT DISTINCT ...) to get the LIST
of values
2. max visitor (Postgis: SELECT max ...) to get the default value
For most datasets (i.e. non-database), this will be 2 full scans
of the dataset.
Hum... that's debatable imho, only dumb datasets are really forced
into full scans.
Shapefile certainly cannot optimize out the visitors, but other data
stores
could if code was added to them.
E.g., SOLR and Mongo can both execute max visitor fast, but there is
no optimized implementation in the store.
What's annoying is that there is no way to know if a store can
optimize these operations.
Since these calls are part of GetCapabilities, would it make sense to
add some handling to the DataStore API / ContentDataStore abstract
implementation (or worst case, the docs)?
With a change like that, it might make it easier for developers (both
implementing and reading/understanding) to see what is going on. The
default abstract implementation could have some safe guards in place to
prevent full-table scans.
Thoughts?
Jim
That said, time based data requires a index to operate efficiently
(all request will hit a specific
time or time range) so... well... you definitely don't want to run it
off a shapefile or other
non indexed source. And if there is an index, both those operations
should be easy to optimize
(given developer time).
About static vs dynamic, both have their own use case, what we have
today in GeoServer
is the case that sponsored the original functionality (e.g. data
mostly static from the spatial
p.o.v. and changing quite aggressively on the temporal p.o.v.), full
dynamic bboxes
and cached/configured dimensions values both make sense and their
support could
be created given enough development resources.
Cheers
Andrea
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