[postgis-users] Cascaded Union Aggregate function

Mon Oct 6 02:27:25 PDT 2008

Dane,

Thanks for testing this out.

That sounds about right.  Yah sorry I missed that bottom part of your
ST_Union.  I realized that after the fact.  Have you ever tried running it
against the whole dataset (I mean union the whole table into a single
geometry) with ST_Union.  That was the one I was testing.  My timings for
your example look about the same.  

That's strange though that OpenJump finishes in 46.3 seconds.  I would have
expected it to do better.  Were you using the snapshot build?  The
production version doesn't have the Cascade Union functionality in it. 

Thanks,
Regina

  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Dane
Springmeyer
Sent: Monday, October 06, 2008 1:46 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Cascaded Union Aggregate function

Regina, 

On Oct 5, 2008, at 10:29 AM, Paragon Corporation wrote:

I was afraid to try this using the current ST_Union (you remember by chance
how long your below takes with ST_Union?)

Oh, I missed addressing this question in my last email. Yes, I indicated how
long ST_Union took below (it took 2.49 minutes).

I tried unioning the shape in OpenJump version that has the cascade union
and it took about 5 minutes.  

I've never used  OpenJump  before but just loaded it up and went  to TOOLS>
Analysis > Union by attribute value. Then I ran that tool with all the
options checked using the same attribute field of 'wholedrain'.

I figure this is the equivalent of this query: 'select
upgis_cascadeunion(the_geom) from npsa group by wholedrain' which ran in
50.91 seconds. The OpenJump query took 46.3 seconds.

Cheers,

Dane

I'll have to try that again since in all the tests
I have run OpenJump has always been faster (unfortunately where I am at the
moment, my PostgreSQL is running on server and OpenJump with shape locally,
so that may not have been a fair test).  But it seems to end up with the
same number of points of 163,612.

Thanks,
Regina

  _____  

From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Dane
Springmeyer
Sent: Sunday, October 05, 2008 12:59 PM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Cascaded Union Aggregate function

Regina, 

Great, my query now works with your amended upgis function posting.

So, here are my timing outputs for the dataset on watersheds I just sent a
reference to:

select count(*) from npsa;
--3162 records

select st_cascadeunion(the_geom) from npsa group by wholedrain;
-- 48.39 sec

select upgis_cascadeunion(the_geom) from npsa group by wholedrain;
-- 50.91 sec

select ST_Union(the_geom) from npsa group by wholedrain;
-- 2.49 minutes

select ST_Collect(the_geom) from npsa group by wholedrain;
-- 10.73 seconds

Next chance I get I'll take a look at the actual results.

Thanks!
Dane

On Oct 5, 2008, at 5:53 AM, Paragon Corporation wrote:

Dane,
Dane,
Oops sorry about that .  I just posted a revised version.  Can you try that
out?  Thanks.

Also can you send me a sample of your data off list.  I think the issue was
I was experimenting with array_append vs. st_geom_accum and I had gotten the
error you described below, but then was unable to replicate it again.

It could be the detoasting affect of st_geom_accum that Mark had described
was the difference between the two. 

Thanks,
Regina

-----Original Message-----
From: postgis-users-bounces at postgis.refractions.net
[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of Dane
Springmeyer
Sent: Sunday, October 05, 2008 1:47 AM
To: PostGIS Users Discussion
Subject: Re: [postgis-users] Cascaded Union Aggregate function

Hi Regina,

Thank you so much for the wiki posting. I've been using your code from your
august 12th email with great success, if not joy. What an amazing speed
improvement, especially for such a critical function. This was your exact
email of code I have working:
http://postgis.refractions.net/pipermail/postgis-devel/2008-August/003412.ht
ml

I've just downloaded the new code off the wiki, but I'm getting an error of
'Unknown Geometry Type: 0'. I'll paste the whole error below in case you
have an idea what might be going on. I'm running mac 10.5 with these
details:

            postgis_version
---------------------------------------
 1.3 USE_GEOS=1 USE_PROJ=1 USE_STATS=1
(1 row)

--------------------------------------------------------------
 PostgreSQL 8.3.3 on i386-apple-darwin9.4.0, compiled by GCC

Cheers,

Dane

-- full error:
test=# select upgis_cascadeunion(the_geom) from npsa group by wholedrain;

ERROR:  Unknown geometry type: 0
CONTEXT:  SQL function "upgis_dump_collect_garray" statement 1
SQL statement "SELECT   
upgis_dump_collect_garray( array_append(ARRAY(SELECT  $1 [s] As geom FROM
generate_series(1,  $2 ) As s WHERE NOT (s = ANY( $3 )) ),  
st_unite_garray(ARRAY(SELECT  $1 [s] As geom FROM generate_series(1,   
$2 ) As s WHERE s = ANY( $3 ) ) ) ) )"
PL/pgSQL function "st_collect_unite_garray" line 29 at assignment SQL
statement "SELECT  upgis_unitecascade_garray(ARRAY(SELECT
st_collect_unite_garray( $1 [i:least(i +  $2  - 1, $3 )]) As geom FROM
generate_series(1,  $3 , $2 ) As i),  $4  + 1,  $5 , false)"
PL/pgSQL function "upgis_unitecascade_garray" line 48 at assignment
SQL statement "SELECT   
upgis_dump_collect_garray( array_append(ARRAY(SELECT  $1 [ $2 [s]] As geom
FROM generate_series(1, array_upper( $2 ,1)) As s ),
upgis_unitecascade_garray(ARRAY(SELECT  $1 [s] As geom FROM  
generate_series(1,  $3 ) As s WHERE NOT (s = ANY( $2 )) ),  $4  + 1,   
$5 , true) ) )"
PL/pgSQL function "upgis_unitecascade_garray" line 33 at assignment SQL
function "upgis_unitecascade_garray_sort" statement 1

On Oct 4, 2008, at 4:53 PM, Paragon Corporation wrote:

Oops sorry about that.

Just realized I had ugly spaces in the link.  I've changed it.  Use 

this one

http://postgis.refractions.net/support/wiki/index.php?upgis_cascadeuni

on

-----Original Message-----

From: postgis-users-bounces at postgis.refractions.net

[mailto:postgis-users-bounces at postgis.refractions.net] On Behalf Of 

Paragon Corporation

Sent: Saturday, October 04, 2008 7:44 PM

To: 'PostGIS Users Discussion'

Subject: [postgis-users] Cascaded Union Aggregate function

For those people who have unions to do that are slow, feel free to try 

out this aggregate union function.

I haven't tested it enough for it to make it into 1.3.4, but have 

included a link to the source code in the wiki.  It should work just 

fine on PostGIS versions 1.2.2 and above.

http://postgis.refractions.net/support/wiki/index.php?PL%2FPGSQL%20Pse

udo%20 Cascade%20Union%20Aggregate%20Function

Let me know if you run into any problems with it.  It has worked well 

for the samples I have used it on.

Thanks,

Regina

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