[postgis] Next Level Redux

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[postgis] Next Level Redux

Paul Ramsey-2
I would be happier flying into the group in my Bell JetRanger with the
'Ride of the Valkyries' playing... however, the news is not all that
triumphant:

I have done the rounds of (almost) all the Canadian federal contacts I
have or have had provided, some prominant people in the local provincial
government, and have not been able to turn up a partner for a proposal
to GeoInnovations for this funding round. (For those not in on the
original newsflash, GeoInnovations is a Canadian Federal Gov't program
to promote geomatics R&D. It provides a 50% cost-sharing of selected R&D
projects. If we put in a proposal, we would have to either cover the
remaining 50% ourselves or find a partner to take up some of that slack.
We were looking to cover 25% ourselves and find a partner for the
remaining 25%. The total dollars we needed to fund our $CA 120K project
were therefor about 30K from outside sources. I should also note that as
a company we are only 5 people, and have very limited resources to
self-fund this. The only reason we are getting so much work done lately
is because paying consulting work has been slow and we have idle hands:
our pain is the community's gain. :) )

Both Red Hat and Greatbridge are currently hoarding cash. Red Hat to try
and remain profitable, and Greatbridge to try and remain solvent. The
upshot is, they were not willing to be one of the project partners. Both
were open to pursuing GIS extensions in the future in happier times
however.

Anyhow, the gate is closing on GeoInnovations, since there are only two
weeks left until the proposal closing date, so I fear we will not be
able to take advantage of that particular opportunity. From a magnitude
point of view (compared to the kinds of dollars dropped on things like
dead simple Oracle db implementations), getting PostGIS/PostgreSQL up to
99% OpenGIS compliance is an astonishly small project: under $100K US
dollars. Somewhere, somehow, there is an organization with a commitment
to PostgreSQL that needs/wants that functionality. We will be working
our way there, however slowly, over the next 12 to 18 months anyways,
but keep your fingers crossed that someone wants to get there
faster/sooner.

>From the front,
Paul

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RE: [postgis] Next Level Redux

Rob Hranac
Hi Paul,

I don't know if this is helpful or not, but we seem to have similar goals.
I can't offer money, but I can offer development services.  I am keenly
interested in developing an open source WFS with database support and,
clearly PostGIS is the best candidate for this.  Any thoughts on this?  I am
not sure if this is what you mean by getting PostGIS up to OpenGIS
compliance or are you interested in the Simple Features Specification for
SQL.  Either way, let me know what you think.  I have been talking to Frank
Warnerdam about this, who I believe is an associate of yours, if I am
reading things correctly.

Cheers,
Rob Hranac

-----Original Message-----
From: Paul Ramsey [mailto:[hidden email]]
Sent: Tuesday, August 14, 2001 1:05 PM
To: [hidden email]
Subject: [postgis] Next Level Redux


I would be happier flying into the group in my Bell JetRanger with the
'Ride of the Valkyries' playing... however, the news is not all that
triumphant:

I have done the rounds of (almost) all the Canadian federal contacts I
have or have had provided, some prominant people in the local provincial
government, and have not been able to turn up a partner for a proposal
to GeoInnovations for this funding round. (For those not in on the
original newsflash, GeoInnovations is a Canadian Federal Gov't program
to promote geomatics R&D. It provides a 50% cost-sharing of selected R&D
projects. If we put in a proposal, we would have to either cover the
remaining 50% ourselves or find a partner to take up some of that slack.
We were looking to cover 25% ourselves and find a partner for the
remaining 25%. The total dollars we needed to fund our $CA 120K project
were therefor about 30K from outside sources. I should also note that as
a company we are only 5 people, and have very limited resources to
self-fund this. The only reason we are getting so much work done lately
is because paying consulting work has been slow and we have idle hands:
our pain is the community's gain. :) )

Both Red Hat and Greatbridge are currently hoarding cash. Red Hat to try
and remain profitable, and Greatbridge to try and remain solvent. The
upshot is, they were not willing to be one of the project partners. Both
were open to pursuing GIS extensions in the future in happier times
however.

Anyhow, the gate is closing on GeoInnovations, since there are only two
weeks left until the proposal closing date, so I fear we will not be
able to take advantage of that particular opportunity. From a magnitude
point of view (compared to the kinds of dollars dropped on things like
dead simple Oracle db implementations), getting PostGIS/PostgreSQL up to
99% OpenGIS compliance is an astonishly small project: under $100K US
dollars. Somewhere, somehow, there is an organization with a commitment
to PostgreSQL that needs/wants that functionality. We will be working
our way there, however slowly, over the next 12 to 18 months anyways,
but keep your fingers crossed that someone wants to get there
faster/sooner.

>From the front,
Paul


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Re: [postgis] Next Level Redux

Paul Ramsey-2
Implementing the Web Feature Server is something I have been thinking
about for a while, and there are two ways of thinking about it.

One is the way Frank is probably thinking of, which is to use the WFS as
an abstraction layer for a bunch of different data sources. This makes
great sense for his OGR library, which is already an abstraction layer.
A WFS based on OGR gets all the OGR-supported data sets for free.

The other way of thinking about it is as an abstraction for a single
data source: a WFS which serves up all the GIS tables in a PostGIS
database. This seems highly redundant, but there is a reason to grant it
consideration. There are performance advantages to specialization, and
maintenance advantages to abstraction.

I think a middle ground is probably going to be the best option in the
end: for things like "spatial databases" in general, the data retrieval,
querying and locking problem will have a particular solution. And for
"file based" data sets, the query, retrieval and locking problem will
have a different solution. The two problems can either be stuffed
together into one system or two WFS servers can be built.

I am also interested to hear what people think about WFS architectures:
long-running processes, or one-shot CGI scripts? Probably the best
possible performance would be from an Apache module, but that might be
alot more work than is necessary, given that the parsing overhead for
the client dealing with GML (!) results will probably vastly outweigh
the retrieval/transformation overhead for the server.

Of course, any WFS implementation will have the same problem which
PostGIS has now: no clients! :)

Rob Hranac wrote:

>
> I don't know if this is helpful or not, but we seem to have similar goals.
> I can't offer money, but I can offer development services.  I am keenly
> interested in developing an open source WFS with database support and,
> clearly PostGIS is the best candidate for this.  Any thoughts on this?  I am
> not sure if this is what you mean by getting PostGIS up to OpenGIS
> compliance or are you interested in the Simple Features Specification for
> SQL.  Either way, let me know what you think.  I have been talking to Frank
> Warnerdam about this, who I believe is an associate of yours, if I am
> reading things correctly.
>
> Cheers,
> Rob Hranac
>
> -----Original Message-----
> From: Paul Ramsey [mailto:[hidden email]]
> Sent: Tuesday, August 14, 2001 1:05 PM
> To: [hidden email]
> Subject: [postgis] Next Level Redux
>
> I would be happier flying into the group in my Bell JetRanger with the
> 'Ride of the Valkyries' playing... however, the news is not all that
> triumphant:
>
> I have done the rounds of (almost) all the Canadian federal contacts I
> have or have had provided, some prominant people in the local provincial
> government, and have not been able to turn up a partner for a proposal
> to GeoInnovations for this funding round. (For those not in on the
> original newsflash, GeoInnovations is a Canadian Federal Gov't program
> to promote geomatics R&D. It provides a 50% cost-sharing of selected R&D
> projects. If we put in a proposal, we would have to either cover the
> remaining 50% ourselves or find a partner to take up some of that slack.
> We were looking to cover 25% ourselves and find a partner for the
> remaining 25%. The total dollars we needed to fund our $CA 120K project
> were therefor about 30K from outside sources. I should also note that as
> a company we are only 5 people, and have very limited resources to
> self-fund this. The only reason we are getting so much work done lately
> is because paying consulting work has been slow and we have idle hands:
> our pain is the community's gain. :) )
>
> Both Red Hat and Greatbridge are currently hoarding cash. Red Hat to try
> and remain profitable, and Greatbridge to try and remain solvent. The
> upshot is, they were not willing to be one of the project partners. Both
> were open to pursuing GIS extensions in the future in happier times
> however.
>
> Anyhow, the gate is closing on GeoInnovations, since there are only two
> weeks left until the proposal closing date, so I fear we will not be
> able to take advantage of that particular opportunity. From a magnitude
> point of view (compared to the kinds of dollars dropped on things like
> dead simple Oracle db implementations), getting PostGIS/PostgreSQL up to
> 99% OpenGIS compliance is an astonishly small project: under $100K US
> dollars. Somewhere, somehow, there is an organization with a commitment
> to PostgreSQL that needs/wants that functionality. We will be working
> our way there, however slowly, over the next 12 to 18 months anyways,
> but keep your fingers crossed that someone wants to get there
> faster/sooner.
>
> From the front,
> Paul
>
> To unsubscribe from this group, send an email to:
> [hidden email]
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
> To unsubscribe from this group, send an email to:
> [hidden email]
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/

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Re: [postgis] Next Level Redux

Paul Ramsey-2
In reply to this post by Rob Hranac
Rob Hranac wrote:
> I am
> not sure if this is what you mean by getting PostGIS up to OpenGIS
> compliance or are you interested in the Simple Features Specification for
> SQL.  Either way, let me know what you think.  I have been talking to Frank
> Warnerdam about this, who I believe is an associate of yours, if I am
> reading things correctly.

If by associate you mean "another damned Canadian", yes. :) Frank is an
open-source GIS fixture, and we newcomers owe alot to him already.

By bringing PostGIS up to spec, I mean finishing all the Simple Features
for SQL functions specified by OpenGIS. These include some very hard
functions, like intersection, unions and buffers. Doing that work is the
other half of having an OpenGIS spatial database. The first half,
supporting the input/output formats and the easier accessors functions,
and having spatial indexing, is already in PostGIS.

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     | Email: [hidden email]
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Re: [postgis] Next Level Redux

Frank Warmerdam
In reply to this post by Paul Ramsey-2
Paul Ramsey wrote:

>Implementing the Web Feature Server is something I have been thinking
>about for a while, and there are two ways of thinking about it.
>
>One is the way Frank is probably thinking of, which is to use the WFS as
>an abstraction layer for a bunch of different data sources. This makes
>great sense for his OGR library, which is already an abstraction layer.
>A WFS based on OGR gets all the OGR-supported data sets for free.
>
Paul,

Certainly I am eventually interested in an OGR based WFS; though; I wouldn't
really be in a strong position to implement transactional capabilities
well.  This
works best when run against a real database - PostGIS in this case.

>I am also interested to hear what people think about WFS architectures:
>long-running processes, or one-shot CGI scripts? Probably the best
>possible performance would be from an Apache module, but that might be
>alot more work than is necessary, given that the parsing overhead for
>the client dealing with GML (!) results will probably vastly outweigh
>the retrieval/transformation overhead for the server.
>
It would depend on your language of implementation.  Because so much is
separated out into the database which has it's own concept a long running
process for maintaining some state and caching I would hope a light cgi-bin
impelementation would be fine.  Of course, I don't know too much about
how Java stuff is done in a web environment.  You certainly don't want to
start a JVM for each call.

>Of course, any WFS implementation will have the same problem which
>PostGIS has now: no clients! :)
>
Well, there are a few WFS clients in existance now - including GeoMedia
(or at
least an upcoming GeoMedia) but you are right that there wouldn't be too
much.

Best regards,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, [hidden email]
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent




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Re: [postgis] Next Level Redux

Paul Ramsey-2
Frank Warmerdam wrote:

> It would depend on your language of implementation.  Because so much is
> separated out into the database which has it's own concept a long running
> process for maintaining some state and caching I would hope a light cgi-bin
> impelementation would be fine.  Of course, I don't know too much about
> how Java stuff is done in a web environment.  You certainly don't want to
> start a JVM for each call.

Laugh if you will, but I was actually thinking about perl... one can
prototype with a CGI and go long-running with mod_perl when performance
is a problem. The thing about transactional stuff is that you run up
against one of the interesting and silly quirks that doing GIS
operations over HTTP gives you:

1-  Client to WFS: Lock feature X!
1-  WFS to Client: Locked.
2-  Client to WFS: Here's an update to feature X!
2-  WFS to Client: OK, thanks.

HTTP session 1 actually *ends* and session 2 is a completely new
connection. If you have a simple CGI, it will shut down and lose all its
state between connection 1 and 2. For database purposes, this means you
lose your connection to the database, and hence also your transaction,
*oof*! So for simple CGI, you have to do the locking *yourself*, fun!
However, with a long-running process, you can maintain your database
connection between HTTP requests, and therefore can delegate the
maintenance of the lock to the database. The trick then is matching up
clients to their locks: I have to go back to the spec, I am assuming a
lock request generates a lock key for the client.

> Well, there are a few WFS clients in existance now - including GeoMedia
> (or at
> least an upcoming GeoMedia) but you are right that there wouldn't be too
> much.

That's good news... I guess nothing from ESRI though :)

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Re: [postgis] Next Level Redux

Paul Ramsey-2
In reply to this post by Paul Ramsey-2
Here is a graphic view of an OpenGIS "chain-of-being" using open-source
components. The missing bits of infrastructure are dotted lines. Note
that this is note the end-all and be-all of OpenGIS architectures: there
are lots of different ways to present a picture of OpenGIS. This is
arguably one of the less compelling ones. A more compelling picture has
independant organizations interoperating via an exposed layer of OpenGIS
services. So, I may use <Product X> for all my GIS work and data
storage, but organizations on the outside never see that, all they see
is my features exposed with a Web Feature Server, and my maps exposed
with a Web Map Server.

One of the reasons for using PostGIS/PostgreSQL for feature storage (on
of the future reasons) is that you need to support the OpenGIS
predicates and spatial operations in order to fully implement the WFS
spec. You also need transactional capabilities to support the updating
portion of the WFS spec.

--
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RE: [postgis] Next Level Redux

Rob Hranac
I think this is a great diagram and gives a very accurate read on the
situation.  It looks like Vision For New York (and I) will undertake the
development of the Web Feature Server portion of this (likely in Java),
starting in about a week or two (as soon as we are officially an OpenGIS
member and I finish our new site).  My general impression is that this is an
unfulfilled niche, but if I am stepping on toes or duplicating here, let me
know.  I like to work and play well with others!  Social Change Online (that
Aussie co.) claims to have developed a Servlet that an extremely crude start
to this that I will likely work with.

I imagine an openWFS eventually serving as a fully transactional abstraction
layer for lots of data formats, but starting with read-only PostGIS formats.
So, I think, ultimately, the goal is slightly more all-encompasing than in
the diagram, but similar, starting out.  If anyone has any comments or
suggestions, of course, I am all ears.  I have lots of time and a reasonable
amount of experience/skills to do this, but am always interested to hear
from the collective wisdom of Canadians (and others).  I will let people
know when I have something real (or even vaporous) to show for this.

Rob

-----Original Message-----
From: Paul Ramsey [mailto:[hidden email]]
Sent: Thursday, August 16, 2001 2:14 PM
To: Andrew Hallam; [hidden email]
Subject: Re: [postgis] Next Level Redux


Here is a graphic view of an OpenGIS "chain-of-being" using open-source
components. The missing bits of infrastructure are dotted lines. Note
that this is note the end-all and be-all of OpenGIS architectures: there
are lots of different ways to present a picture of OpenGIS. This is
arguably one of the less compelling ones. A more compelling picture has
independant organizations interoperating via an exposed layer of OpenGIS
services. So, I may use <Product X> for all my GIS work and data
storage, but organizations on the outside never see that, all they see
is my features exposed with a Web Feature Server, and my maps exposed
with a Web Map Server.

One of the reasons for using PostGIS/PostgreSQL for feature storage (on
of the future reasons) is that you need to support the OpenGIS
predicates and spatial operations in order to fully implement the WFS
spec. You also need transactional capabilities to support the updating
portion of the WFS spec.

--
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     | Refractions Research
     | Email: [hidden email]
     | Phone: (250) 885-0632
     \_

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Re: [postgis] Next Level Redux

Paul Ramsey-2
Thrills and chills :)

Rob Hranac wrote:
> I think this is a great diagram and gives a very accurate read on the
> situation.  It looks like Vision For New York (and I) will undertake the
> development of the Web Feature Server portion of this (likely in Java),
> starting in about a week or two (as soon as we are officially an OpenGIS
> member and I finish our new site).  My general impression is that this is an
> unfulfilled niche, but if I am stepping on toes or duplicating here, let me
> know.  

I have not heard of an open-source WFS as yet, but I will wait for
confirmation from Frank before assuming :)

> I imagine an openWFS eventually serving as a fully transactional abstraction
> layer for lots of data formats, but starting with read-only PostGIS formats.

Definately a complete abstraction is a nice end goal. Good modular
design will make all of this easier, of course. One thing I will be
looking at pretty early on (once you have built the framework :) is
putting OracleSpatial in there. Open interfaces to proprietary data
sources will help the general ecology of free software. I wonder if
there is a Java interface to SDE? If not a JNI connection could be used,
it would just be less pleasant. Doing the transactional stuff for
file-based data will be fairly tricky, I would guess, particularly in a
write-heavy environment.

> So, I think, ultimately, the goal is slightly more all-encompasing than in
> the diagram, but similar, starting out.  If anyone has any comments or
> suggestions, of course, I am all ears.  I have lots of time and a reasonable
> amount of experience/skills to do this, but am always interested to hear
> from the collective wisdom of Canadians (and others).  I will let people
> know when I have something real (or even vaporous) to show for this.

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[postgis] Web Feature Server

David Blasby-3
Rob Hranac wrote:
> I think this is a great diagram and gives a very accurate read on the
> situation.  It looks like Vision For New York (and I) will undertake the
> development of the Web Feature Server portion of this (likely in Java),
> starting in about a week or two (as soon as we are officially an OpenGIS
> member and I finish our new site).  My general impression is that this is an
> unfulfilled niche, but if I am stepping on toes or duplicating here, let me
> know.  


If I remember correctly, the WFS requires a complete implementation of
the OpenGIS spec.  

By this I mean, you'll have to be able to handle requests like "Give me
everything whose boundary touches this feature buffered by 25 units".
In order to do this you'll have to have relate() and buffer()
functions.  

Since the JTS does this (and its in Java), I suggest you talk to Martin
at Vivid Solutions ([hidden email]).  They will soon be
releasing technology ("JTS") that gives a full implemention of the
OpenGIS simple features.  This will allow you to give WFS support to
datatypes like shapefiles and the like.  Once JTS is in PostGIS, you'll
just be able to hand-off the requests to the postgis server.  Hopefully
you'll also be able to support something like SDE/Oracle Spatial, but
their definition of certain concepts are different than the OpenGIS
spec.

At some point the future, you'll have to add support for locking and
updating.

Its a *GREAT* project, and should be lots of fun.

Does anyone know of a [announced/proposed] WFS client?

dave

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Re: [postgis] Next Level Redux

John Reid-5
In reply to this post by Paul Ramsey-2
  Hi,

There are some other open source efforts that may help provide some of
what you appear to be looking for that I haven't seen any mention of yet
on the list.  I don't know if they might be interested in collaboration.
 Some details, ideas and a healthy dose of questions below:

Paul Ramsey wrote:

>Frank Warmerdam wrote:
>
>>It would depend on your language of implementation.  Because so much is
>>separated out into the database which has it's own concept a long running
>>process for maintaining some state and caching I would hope a light cgi-bin
>>impelementation would be fine.  Of course, I don't know too much about
>>how Java stuff is done in a web environment.  You certainly don't want to
>>start a JVM for each call.
>>
>
>Laugh if you will, but I was actually thinking about perl... one can
>prototype with a CGI and go long-running with mod_perl when performance
>is a problem. The thing about transactional stuff is that you run up
>against one of the interesting and silly quirks that doing GIS
>operations over HTTP gives you:
>
>1-  Client to WFS: Lock feature X!
>1-  WFS to Client: Locked.
>2-  Client to WFS: Here's an update to feature X!
>2-  WFS to Client: OK, thanks.
>
>HTTP session 1 actually *ends* and session 2 is a completely new
>connection. If you have a simple CGI, it will shut down and lose all its
>state between connection 1 and 2
>
Some open source development is currently occuring associated with
resource data directory projects in Australia.  I know they have been
working on distributed retrieval of info with wrappers to desktop data.
 AFAIK mostly read only at this stage.

>For database purposes, this means you
>lose your connection to the database, and hence also your transaction,
>*oof*! So for simple CGI, you have to do the locking *yourself*, fun!
>However, with a long-running process, you can maintain your database
>connection between HTTP requests, and therefore can delegate the
>maintenance of the lock to the database. The trick then is matching up
>clients to their locks: I have to go back to the spec, I am assuming a
>lock request generates a lock key for the client.
>
Could the GoF's connection pool pattern be relevant here?

>>Well, there are a few WFS clients in existance now - including GeoMedia
>>(or at
>>least an upcoming GeoMedia) but you are right that there wouldn't be too
>>much.
>>
Some stuff along these lines must have been done by these projects aimed
at combining and delivering spatial data from different sources:

    * canri/nrdd/social change online (see
      http://www.canri.nsw.gov.au/tech/index.html) - mapserver
      extensions using java, perl for access to distributed data sources.
    * imroc/csiro ( http://imp.cmis.csiro.au/imroc/csiro/about.htm, also
      http://www.cmis.csiro.au/sis/) also svg java toolkit for vector
      graphics.

HTH,

John



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[postgis] Re: SDE Java API

Raj Singh-5
In reply to this post by Paul Ramsey-2
The latest version of SDE (8.1) finally does have a
Java API. I hear it's reasonably functional, but I
haven't used it yet myself.

--- In postgis@y..., Paul Ramsey <pramsey@r...> wrote:
> I wonder if
> there is a Java interface to SDE? If not a JNI connection could be
> used,
> it would just be less pleasant. Doing the transactional stuff for
> file-based data will be fairly tricky, I would guess, particularly
> in a write-heavy environment.


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[postgis] Faster access to WKB (in CVS version)

David Blasby-3
In reply to this post by David Blasby-3
When I was adding the WKB types, I noticed I was printing out debuging
info when converting to WKB.  I've removed it.  

Mapserver (and other WKB applications) should run faster now.

dave
ps. this is in the CVS version

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[postgis] minor workaround to postgreSQL's user defined VARIABLE length datatype default value bug

David Blasby-3
In reply to this post by David Blasby-3
There's a bug in postgresql for variable length user defined types (like
GEOMETRY and WKB).  It sets an invalid default value for the type.

The recommended work around is to modify postgreSQL's pg_type table and
explicitly tell it use NULL as the default value.

I've added these two lines to the bottom of the postgis.sql.in file in
the CVS version:

update pg_type set typdefault = NULL where  typname = 'wkb';
update pg_type set typdefault = NULL where  typname = 'geometry';

Most people will not be affected by this bug so you can ignore this
message, but I thought I'd mention why those two lines are in the file.

dave
ps.  This is how to reproduce the bug;

create table t (i integer,g geometry);
insert into t values (1);
select * from t;
<server crashes>

The server crashes because it actually put an invalid value in the
GEOMETRY column during the insert (its an '-'::text) and postgis doesnt
know what do with it.

Want more info?  Check out the postgresql hacker's mailing list.

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