Re: [postgis-users] Cascaded Union Aggregate function

Sun, 05 Oct 2008 22:49:34 -0700 

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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] ] 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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 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: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] 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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