Subject: Re: Please recommend postgresql.conf improvements for osm2pgsql loading Europe

From: Justin Clift <[email-masked]>
Date: Sat, 30 Mar 2024 13:33:42 +1000

On 2024-03-30 05:53, Alexander Farber wrote:
<snip>
> I use the following postgresql.conf in my Dockerfile
> ( the full version at https://stackoverflow.com/a/78243530/165071 ),
> when loading a 28 GByte large europe-latest.osm.pbf
<snip>
> Is anybody please able to spot any improvements I could
> apply to the postgresql.conf config values at the top of my mail,
> that could reduce the loading time of almost 2 hours?

Not specific conf file improvements, but for an initial data load
have you done things like turning off fsync(), deferring index
creating until after the data load finishes, and that kind of thing?

You don't want fsync() off when you're using the database in
production, but for long data load scenarios it seems like it'd
be a decent fit.

With .pbf files, from skimming over how they're described here:

   https://wiki.openstreetmap.org/wiki/PBF_Format

... they don't seem to be optimised for loading into a database. (?)

It kind of looks like they'd be stored into individual records,
which probably means they'd be getting imported as individual
INSERT statements rather than something that's optimised for
bulk loading. :(

Regards and best wishes,

Justin Clift

---

From: Alexander Farber <[email-masked]>
Date: Sat, 30 Mar 2024 11:04:11 +0100

Thank you, Justin -

> creating until after the data load finishes, and that kind of thing?

I will try the following commands in my Dockerfile then
and later report back on any improvements:

RUN set -eux && \
    pg_ctl init && \
    echo "shared_buffers = 1GB"                >> $PGDATA/postgresql.conf
&& \
    echo "work_mem = 50MB"                     >> $PGDATA/postgresql.conf
&& \
    echo "maintenance_work_mem = 10GB"         >> $PGDATA/postgresql.conf
&& \
    echo "autovacuum_work_mem = 2GB"           >> $PGDATA/postgresql.conf
&& \
    echo "wal_level = minimal"                 >> $PGDATA/postgresql.conf
&& \
    echo "checkpoint_timeout = 60min"          >> $PGDATA/postgresql.conf
&& \
    echo "max_wal_size = 10GB"                 >> $PGDATA/postgresql.conf
&& \
    echo "checkpoint_completion_target = 0.9"  >> $PGDATA/postgresql.conf
&& \
    echo "max_wal_senders = 0"                 >> $PGDATA/postgresql.conf
&& \
    echo "random_page_cost = 1.0"              >> $PGDATA/postgresql.conf
&& \
    echo "password_encryption = scram-sha-256" >> $PGDATA/postgresql.conf
&& \
    echo "fsync = off"                            >>
$PGDATA/postgresql.conf && \
    pg_ctl start && \
    createuser --username=postgres $PGUSER && \
    createdb --username=postgres --encoding=UTF8 --owner=$PGUSER
$PGDATABASE && \
    psql --username=postgres $PGDATABASE --command="ALTER USER $PGUSER WITH
PASSWORD '$PGPASSWORD';" && \
    psql --username=postgres $PGDATABASE --command='CREATE EXTENSION IF NOT
EXISTS postgis;' && \
    psql --username=postgres $PGDATABASE --command='CREATE EXTENSION IF NOT
EXISTS hstore;' && \
    osm2pgsql --username=$PGUSER --database=$PGDATABASE --create
--cache=60000 --hstore --latlong /data/map.osm.pbf && \
    rm -f /data/map.osm.pbf && \
    pg_ctl stop && \
    echo "fsync = on"                            >> $PGDATA/postgresql.conf
&& \
    echo '# TYPE DATABASE USER ADDRESS METHOD'                >
$PGDATA/pg_hba.conf && \
    echo "local all postgres peer"                           >>
$PGDATA/pg_hba.conf && \
    echo "local $PGDATABASE $PGUSER           scram-sha-256" >>
$PGDATA/pg_hba.conf && \
    echo "host  $PGDATABASE $PGUSER 0.0.0.0/0 scram-sha-256" >>
$PGDATA/pg_hba.conf

The later fsync = on will override the former, right?

Best regards
Alex

---

From: Alexander Farber <[email-masked]>
Date: Sat, 30 Mar 2024 19:07:38 +0100

Turning fsync = off has resulted in no noticable build time reduction for
my Dockerfile with OSM Europe data, but still thank you for the suggestion!

---

From: Justin Clift <[email-masked]>
Date: Sun, 31 Mar 2024 17:31:28 +1000

> my Dockerfile with OSM Europe data, but still thank you for the 

No worries. :)

With this import you're doing, is it something that will be repeated a 
lot
with the exact same data set, or is this a once off thing?

If it's something that'll be repeated a lot (maybe part of some 
automated
process?), then it might be worth making a backup / snapshot / something
of the database after the import has completed.

With a backup or snapshot in place (depends on the storage you're 
using),
you could potentially load things from that backup / snapshot (etc) 
instead
of having to do the import all over again each time.

Regards and best wishes,

Justin Clift

---

From: hector vass <[email-masked]>
Date: Sun, 31 Mar 2024 16:55:02 +0100

On Sat, 30 Mar 2024, 10:04 Alexander Farber, <[email-masked]>
wrote:

>     psql --username=postgres $PGDATABASE --command="ALTER USER $PGUSER
> WITH PASSWORD '$PGPASSWORD';" && \
>     psql --username=postgres $PGDATABASE --command='CREATE EXTENSION IF
> NOT EXISTS postgis;' && \
>     psql --username=postgres $PGDATABASE --command='CREATE EXTENSION IF
> NOT EXISTS hstore;' && \
>     echo "fsync = on"                            >>

2hrs sounds reasonable for Europe, it's a big place in terms of osm data
and osm2pgsql is doing processing to convert to geometry objects prior to
doing anything on the Postgresql side.
If you examine the --log--sql output for a small test country you can see
what it does in terms of the postgresql.
osm2pgsql gives options to trim the output to only what you need (so if you
don't want waterways, traffic features, parking places or places of worship
etc.. why load them)
Hopefully you have found the excellent geofabrik
https://download.geofabrik.de/ source for osm data.
Rather than load this data afresh each update cycle you would be better off
simply loading the changes so the .osc files or ... osm osmosis will create
the equivalent of a diff file for you
Looks like you are already using osm2psql's recommended postgresql.config
settings, I'd be surprised if this was way off.  Getting as close to tin
rather than virtual machines and containers will also help, lots of io
going on here.
If you are only interested in the geography you might consider geofabrik's
shapefile available for many countries, they have already done some of the
work for you.

Apologies if you are already a long way down this route & just asking about
the final stage of loading the osm2pgsql output to Postgresql but however
well you do here I would only expect small marginal gains.

---

From: Alexander Farber <[email-masked]>
Date: Mon, 1 Apr 2024 02:37:50 +0200

Thank you for the insights