Re: performance problem with loading data

Try using COPY instead of insert select, if that is possible for you.
It is much faster than insert.

Otherwise, you might try dropping the index and constraint, loading the
data, and recreating the index and constraint.

________________________________

From: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Sergey Karin
Sent: Saturday, June 09, 2007 1:48 AM
To: pgsql-general(at)postgresql(dot)org; PostGIS Users Discussion
Subject: [GENERAL] performance problem with loading data

Hi all.

I use PG 8.1.8 and PostGIS 1.1.1
vka1=# select version();
version
------------------------------------------------------------------------
-----------------------------------------
PostgreSQL 8.1.8 on x86_64-pc-linux-gnu, compiled by GCC cc (GCC) 4.1.2
20061115 (prerelease) (Debian 4.1.1-21)

vka1=# select postgis_full_version();
postgis_full_version
------------------------------------------------------------------------
----------
POSTGIS="1.1.1" GEOS="2.2.3-CAPI-1.1.1" PROJ="Rel. 4.4.9, 29 Oct 2004"
USE_STATS

I develop application for loading geodata to database. In separate
transaction the application inserts the data in separate table that
created dynamically when transaction started. All tables has equal
structure.

Geodata has simple and similar structure (field geometry): POLYGON((x1
y1, x2 y2, x3 y3, x4 y4, x1 y1))
For loading geodata I use INSERT into <TABLE_NAME> .... via LIBPQ.
In big loop I call PQexec(conn, query).

I found *VERY* strange problem: speed of the loading process is slow
down (first 10000 objects are loaded in 69792 ms and last 10000 objects
in 123737 ms). And futhermore, if I do NOT close current session but
start new transaction, the first 10000 objects will be loaded in 192279
ms and last 10000 objects in 251742 ms. And so on!! :-(

But if I drop the trigger speed of loading process is NOT slow down.

Who can explain me what I do incorrect?

Thanks in advance

Sergey Karin

=======================================
================code===================
=======================================
create table <TABLE_NAME> (
GID SERIAL not null,
GEOM_ORDER INT4 not null default 0,
ZOOMABLE BOOL not null default
false,
GEOM GEOMETRY
constraint <TABLE_NAME_GID> primary key (GID),
);

create index <TABLE_NAME_GEOM_INDEX> on <TABLE_NAME> using gist ( geom
gist_geometry_ops );
create trigger trgOInsert
before insert or update
on <TABLE_NAME>
for each row
execute procedure oInsertCheck('GEOMETRYCOLLECTION',
0);

create or replace function oInsertCheck() returns trigger as'
declare
g_isvalid boolean;
iSrid int4;
geomType varchar;
begin

if(new.geom isnull) then
new.geom := geomFromText(\'GEOMETRYCOLLECTION(EMPTY)\');
end if;
if(new.geom_order isnull) then
new.geom_order := 0;
end if;

select isvalid(new.geom) into g_isvalid;
if(g_isvalid isnull) then
return NULL;
end if;

geomType := TG_ARGV[TG_NARGS-2];
iSrid := TG_ARGV[TG_NARGS-1];

if(upper(geomType) = \'GEOMETRYCOLLECTION\') then
new.geom := force_collection(new.geom);
end if;

new.geom := setSrid( new.geom, iSrid);

return new;
end
'language 'plpgsql' security definer;

=================end of code==========================