Hallo I have been struggling with the same task. I don't know if I have solved it because I ran out of time a few months ago. But I attach the sql as a file with some descriptive texts. I intend to check it more properly and write some tutorial, but that will take some time before I can do. So, no guarantees :-) /Nicklas
2010-01-14 Nicolas Gillet - MARKET-IP wrote:
>
Hello,
I have a big shape file to process (about 300 Mo, 1.5 million records)
I have to aggregate the touching linestrings having the same attributes
therefore the best way I could find (with help of this mailing list) was to
aggregate all the linestrings with the same attribute and then splitting the
ones that dont touch.
Here is the query :
SELECT subQ.id, subQ.feattyp, subQ.frc, subQ.shieldnum, subQ.name, null,
(st_dump(merged_geom)).geom AS the_geom
FROM (
SELECT MAX(id) AS id, feattyp, frc, MAX(shieldnum) AS
shieldnum, nw.name, ST_LineMerge(ST_Collect(the_geom)) AS merged_geom
FROM nw
WHERE nw.frc >= 0
GROUP BY nw.name, nw.feattyp, nw.frc
) AS subQ;
This has worked fine on smaller shapes but on this one I get an out of memory
error.
I used pgTune to change database default settings and the result is as follow :
#custom_variable_classes = '' # list of custom variable class
names
default_statistics_target = 50 # pgtune wizard 2010-01-13
maintenance_work_mem = 120MB # pgtune wizard 2010-01-13
constraint_exclusion = on # pgtune wizard 2010-01-13
effective_cache_size = 1408MB # pgtune wizard 2010-01-13
work_mem = 12MB # pgtune wizard 2010-01-13
wal_buffers = 8MB # pgtune wizard 2010-01-13
checkpoint_segments = 16 # pgtune wizard 2010-01-13
shared_buffers = 480MB # pgtune wizard 2010-01-13
max_connections = 80 # pgtune wizard 2010-01-13
All the other parameters have their default values.
What can I do to run my script through this heavy shape files ?
Thank you
Nicolas.
merge_lines_in_big_table.sql
Description: Binary data
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