Hi Maja,
Ian's dead-on. If you are calling to InfluxDB directly, your options
are to handle certain filters manually (which is great for a prototype!)
or implement a visitor (again, you can focus on certain predicates first).
As an alternative solution, it appears that there is at least one JDBC
connector for InfluxDB (https://github.com/influxdata/influxdb-java).
You could plug that JDBC connector into the general GeoTools
JDBCDataStore by mirroring what is done in the PostGIS DataStore.
The advantage of the first approach is that you'd be plumbing things
directly, and it might be more clear what is happening. With the JDBC
approach, the general GeoTools FilterToSQL code would do lots of the
heavy lifting for you, so that's win. On the downside, you'd have to
learn an extra level of abstraction and you'd be reliant on the JDBC
implementation.
As Ian said, this is a somewhat uncommon task, so asking on the lists
would be a great way to get more help! Also, I hope you can share your
implementation; wiring up InfluxDB to GeoServer sounds like a great project!
Cheers,
Jim
As a concrete example of a non-trivial, non-sql visitor, check out this
class from ElasticGeo:
https://github.com/ngageoint/elasticgeo/blob/master/gt-elasticsearch-parent/gt-elasticsearch-core/src/main/java/mil/nga/giat/data/elasticsearch/FilterToElastic.java.
If you are willing to read Scala, check out this which maps CQL to
CQEngine queries:
https://github.com/locationtech/geomesa/blob/master/geomesa-memory/geomesa-cqengine/src/main/scala/org/locationtech/geomesa/memory/cqengine/utils/CQEngineQueryVisitor.scala
with unit tests:
https://github.com/locationtech/geomesa/blob/master/geomesa-memory/geomesa-cqengine/src/test/scala/org/locationtech/geomesa/memory/cqengine/utils/CQEngineQueryVisitorTest.scala.
GeoMesa has a few other visitors here and there; I think that one is the
easiest to read.
If you haven't seen it, this tutorial should help with the general
datastore bits:
http://docs.geotools.org/stable/userguide/tutorial/datastore/index.html
On 01/17/2017 08:23 AM, Ian Turton wrote:
You need to look at (for example) PostgisFilterToSQL - which is where
the generic GeoTools filter is converted to the database specific SQL
query. The *FilterToSQL classes are written as visitors which walk
down the filter tree and carry out an operation at each node of the
tree. Other DB specific parts of the query (encoding geometry etc)
are handled in the Dialect class.
IFAIK there is no tutorial for this as it isn't something that gets
done very often, your best bet is to discuss any problems you run in
to on the GeoTools lists.
Ian
On 17 January 2017 at 11:48, Firefly <[email protected]
<mailto:[email protected]>> wrote:
Hi,
So I've managed to make DataStore that connects to InfuxDB and
fetches the
data. Now, I would like to implement filtering with CQL, so that I
don't
fetch all data from DB, but only the ones that I specify.
Specifically, based on the parameters I enter (for example 4/10
parameters),
I would execute specific InfluxQL query on database and fetch data
with only
those 4 parameters.
I think that postgis plugin works that way, you specify the
parameters in
CQL and from it the SQL query is created and only specified data
is fetched.
I want to accomplish basically the same thing.
I was wondering is there any tutorial/documentation for this,
where I can
find how to implement this kind of filtering? What is the best
approach
regarding this?
Best regards,
Maja
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