The attrib column is a piece of arbitrary text that can be attached to a
feature... possibly the postgis driver should be modified to allow it to
be optional, but at the moment you need to create a varchar or similar
column called attrib, it can be empty, it just has to exist.
Paul Osmialowski wrote:
> Hi again,
> It was a nice surprise for me, playerv supports vectormap interface.
> However I couldn't make use of it: after few hours of fighting with uDIG
> utility I've prepared some map and stored it in the database. To create a
> base I've followed advices from vectormap.cc comments:
> create table obstacles(ID int4, NAME varchar(25));
> select AddGeometryColumn('public', 'obstacles', 'geom', 423, 'LINESTRING',
> Three columns were created: ID, NAME and GEOM. Unfortunately, in order to
> read layer data, postgis Player driver executes such a query:
> SELECT name, asbinary(geom), attrib FROM obstacles;
> This made Player to fail due to lack of column called `attrib`.
> What ta hell the `attrib` column is?! Can you give me any hint how it
> should be created.
> On Thu, 31 Jan 2008, Toby Collett wrote:
>> You are right that it hasnt been implemented yet, the usual issue with FOSS
>> that features generally get written as they are needed and we havent needed
>> the update ability yet (Ben works with me which is why I have been answering
>> most of the vectormap questions :)
>> In theory implementing the update code should be relatively simple, you need
>> to reverse the process of the select query with an insert or update query in
>> the driver, and of course implement the c client library methods for it. As
>> always happy to accept patches for this stuff, but we are not likely to
>> implement it ourselves in the next couple of months.
>> The only complication of updates, is if you alow modifcation rather than
>> just addition to a layer, then you need to be able to match features by
>> their ID or some such...
>> On 31/01/2008, Paul Osmialowski <newchief@...> wrote:
>>> Hi Toby,
>>> I'm writing this directly to you since you're always replying to my posts
>>> about vectormap interface and postgis driver. From time to time I'm
>>> finding some more free time to look at rarely used features of Player.
>>> Since I'd like to look closer at spatial reasoning, I'm trying to do
>>> anything interesting with vectormap interface and postgis driver. I was
>>> wondering if it is possible to update a layer of postgis map from player
>>> client application. Vectormap interface defines
>>> PLAYER_VECTORMAP_REQ_WRITE_LAYER request. To my surprise, libplayerc does
>>> not provide any function for that request. I wanted to release a patch for
>>> dev_vectormap.c that implements playerc_vectormap_write_layer_data()
>>> function, but right after I started suddenly I got curious how this
>>> request is handled by postgis driver. To my surprise it is handled like
>>> void PostGIS::RequestLayerWrite(player_vectormap_layer_data_t* data)
>>> Now I know why no one implemented write function in the client library.
>>> Something must be changed. Unfortunately I have no idea how it should be
>>> implemented as it is Ben Morelli's driver and I guess only he knows what
>>> should be done there.
>>> At the end I'd like to write simple client application that takes vectors
>>> from subscribed map interface (PLAYER_MAP_REQ_GET_VECTOR request), builds
>>> a layer from those vectors and writes it to the postgis database using
>>> subscribed vectormap interface. That would be for the start (player does
>>> not provide any examples of postgis maps, my converting application would
>>> give me them).
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