[pdal] readers.pgpointcloud

[Mike Skaug]

I'm working on a project where we are using pdal to ingest lidar data 
into a pgpointcloud enabled PostgreSQL database and then reading the 
data out into another format. At least that's the idea.

We set up a simple pipeline to write the data into the database:
{
     "pipeline":[
"/data/ILATM1B.002/2013.03.20/ILATM1B_20130320_141441.ATM4BT4.h5",
         {
             "type": "filters.chipper",
             "capacity": 500
         },
         {
             "type":"writers.pgpointcloud",
             "connection":"host='valkyrie-db' dbname='valkyrie' 
user='valkyrie' password='valkyrie'",
             "table":"patches"
         }
     ]
}

This reads a single file, chips it and writes it into the database. This 
works as expected.

However, this pipeline taken almost verbatim from the example: 
http://www.pdal.io/stages/readers.pgpointcloud.html, which is intended 
to read the data out of the database, fails:

{
     "pipeline":[
         {
             "type":"readers.pgpointcloud",
             "connection":"host='valkyrie-db' dbname='valkyrie' 
user='valkyrie' password='valkyrie'",
             "table":"patches",
             "column":"pa",
             "where":"PC_Explode(PC_Intersection(pa, 
'SRID=4326;POLYGON((-160.000 80.000, -20.000 80.00, -20.000 85.000, 
-160.000 85.000, -160.000 80.000))'::geometry))"
         },
         {
           "type":"writers.text",
           "filename":"output.txt"
         }
     ]
}

The error is `PDAL: JSON pipeline: Can't find file ' ' to open with 
'readers.pgpointcloud'.`

This seems to suggest that pdal is looking for an input file? Or might I 
get this error if it is not connecting to the database? (I assume that 
the database connection is fine because it is using the same 
`connection` option as the successful "writers.pgpointcloud" given above.)

Thanks for any suggestions.
--Mike