Nominatim/docs/admin/Import-and-Update.md

Importing and Updating the Database

The following instructions explain how to create a Nominatim database from an OSM planet file and how to keep the database up to date. It is assumed that you have already successfully installed the Nominatim software itself, if not return to the installation page.

Configuration setup in settings/local.php

The Nominatim server can be customized via the file settings/local.php in the build directory. Note that this is a PHP file, so it must always start like this:

<?php

without any leading spaces.

There are lots of configuration settings you can tweak. Have a look at settings/default.php for a full list. Most should have a sensible default.

Flatnode files

If you plan to import a large dataset (e.g. Europe, North America, planet), you should also enable flatnode storage of node locations. With this setting enabled, node coordinates are stored in a simple file instead of the database. This will save you import time and disk storage. Add to your settings/local.php:

@define('CONST_Osm2pgsql_Flatnode_File', '/path/to/flatnode.file');

Replace the second part with a suitable path on your system and make sure the directory exists. There should be at least 64GB of free space.

Downloading additional data

Wikipedia/Wikidata rankings

Wikipedia can be used as an optional auxiliary data source to help indicate the importance of OSM features. Nominatim will work without this information but it will improve the quality of the results if this is installed. This data is available as a binary download:

cd $NOMINATIM_SOURCE_DIR/data
wget https://www.nominatim.org/data/wikimedia-importance.sql.gz

The file is about 400MB and adds around 4GB to Nominatim database.

!!! tip If you forgot to download the wikipedia rankings, you can also add importances after the import. Download the files, then run ./utils/setup.php --import-wikipedia-articles and ./utils/update.php --recompute-importance.

Great Britain, USA postcodes

Nominatim can use postcodes from an external source to improve searches that involve a GB or US postcode. This data can be optionally downloaded:

cd $NOMINATIM_SOURCE_DIR/data
wget https://www.nominatim.org/data/gb_postcode_data.sql.gz
wget https://www.nominatim.org/data/us_postcode_data.sql.gz

Choosing the Data to Import

In its default setup Nominatim is configured to import the full OSM data set for the entire planet. Such a setup requires a powerful machine with at least 64GB of RAM and around 800GB of SSD hard disks. Depending on your use case there are various ways to reduce the amount of data imported. This section discusses these methods. They can also be combined.

Using an extract

If you only need geocoding for a smaller region, then precomputed extracts are a good way to reduce the database size and import time. Geofabrik offers extracts for most countries. They even have daily updates which can be used with the update process described below. There are also other providers for extracts.

Please be aware that some extracts are not cut exactly along the country boundaries. As a result some parts of the boundary may be missing which means that Nominatim cannot compute the areas for some administrative areas.

Dropping Data Required for Dynamic Updates

About half of the data in Nominatim's database is not really used for serving the API. It is only there to allow the data to be updated from the latest changes from OSM. For many uses these dynamic updates are not really required. If you don't plan to apply updates, the dynamic part of the database can be safely dropped using the following command:

./utils/setup.php --drop

Note that you still need to provide for sufficient disk space for the initial import. So this option is particularly interesting if you plan to transfer the database or reuse the space later.

Reverse-only Imports

If you only want to use the Nominatim database for reverse lookups or if you plan to use the installation only for exports to a photon database, then you can set up a database without search indexes. Add --reverse-only to your setup command above.

This saves about 5% of disk space.

Filtering Imported Data

Nominatim normally sets up a full search database containing administrative boundaries, places, streets, addresses and POI data. There are also other import styles available which only read selected data:

• settings/import-admin.style Only import administrative boundaries and places.
• settings/import-street.style Like the admin style but also adds streets.
• settings/import-address.style Import all data necessary to compute addresses down to house number level.
• settings/import-full.style Default style that also includes points of interest.
• settings/import-extratags.style Like the full style but also adds most of the OSM tags into the extratags column.

The style can be changed with the configuration CONST_Import_Style.

To give you an idea of the impact of using the different styles, the table below gives rough estimates of the final database size after import of a 2018 planet and after using the --drop option. It also shows the time needed for the import on a machine with 64GB RAM, 4 CPUS and SSDs. Note that the given sizes are just an estimate meant for comparison of style requirements. Your planet import is likely to be larger as the OSM data grows with time.

style	Import time	DB size	after drop
admin	5h	190 GB	20 GB
street	42h	400 GB	180 GB
address	59h	500 GB	260 GB
full	80h	575 GB	300 GB
extratags	80h	585 GB	310 GB

You can also customize the styles further. For a description of the style format see the development section.

Initial import of the data

!!! danger "Important" First try the import with a small extract, for example from Geofabrik.

Download the data to import and load the data with the following command from the build directory:

./utils/setup.php --osm-file <data file> --all 2>&1 | tee setup.log

Note for full planet imports: Even on a perfectly configured machine the import of a full planet takes at least 2 days. Once you see messages with Rank .. ETA appear, the indexing process has started. This part takes the most time. There are 30 ranks to process. Rank 26 and 30 are the most complex. They take each about a third of the total import time. If you have not reached rank 26 after two days of import, it is worth revisiting your system configuration as it may not be optimal for the import.

Notes on memory usage

In the first step of the import Nominatim uses osm2pgsql to load the OSM data into the PostgreSQL database. This step is very demanding in terms of RAM usage. osm2pgsql and PostgreSQL are running in parallel at this point. PostgreSQL blocks at least the part of RAM that has been configured with the shared_buffers parameter during PostgreSQL tuning and needs some memory on top of that. osm2pgsql needs at least 2GB of RAM for its internal data structures, potentially more when it has to process very large relations. In addition it needs to maintain a cache for node locations. The size of this cache can be configured with the parameter --osm2pgsql-cache.

When importing with a flatnode file, it is best to disable the node cache completely and leave the memory for the flatnode file. Nominatim will do this by default, so you do not need to configure anything in this case.

For imports without a flatnode file, set --osm2pgsql-cache approximately to the size of the OSM pbf file (in MB) you are importing. Make sure you leave enough RAM for PostgreSQL and osm2pgsql as mentioned above. If the system starts swapping or you are getting out-of-memory errors, reduce the cache size or even consider using a flatnode file.

Verify import finished

Run this script to verify all required tables and indices got created successfully.

./utils/check_import_finished.php

Tuning the database

Accurate word frequency information for search terms helps PostgreSQL's query planner to make the right decisions. Recomputing them can improve the performance of forward geocoding in particular under high load. To recompute word counts run:

./utils/update.php --recompute-word-counts

This will take a couple of hours for a full planet installation. You can also defer that step to a later point in time when you realise that performance becomes an issue. Just make sure that updates are stopped before running this function.

If you want to be able to search for places by their type through special key phrases you also need to enable these key phrases like this:

./utils/specialphrases.php --wiki-import > specialphrases.sql
psql -d nominatim -f specialphrases.sql

Note that this command downloads the phrases from the wiki link above. You need internet access for the step.

Installing Tiger housenumber data for the US

Nominatim is able to use the official TIGER address set to complement the OSM house number data in the US. You can add TIGER data to your own Nominatim instance by following these steps. The entire US adds about 10GB to your database.

1. Get preprocessed TIGER 2019 data and unpack it into the data directory in your Nominatim sources:

   cd Nominatim/data wget https://nominatim.org/data/tiger2019-nominatim-preprocessed.tar.gz tar xf tiger2019-nominatim-preprocessed.tar.gz

`data-source/us-tiger/README.md` explains how the data got preprocessed.

2. Import the data into your Nominatim database:

   ./utils/setup.php --import-tiger-data

3. Enable use of the Tiger data in your settings/local.php by adding:

   @define('CONST_Use_US_Tiger_Data', true);
   

4. Apply the new settings:

    ./utils/setup.php --create-functions --enable-diff-updates --create-partition-functions

Updates

There are many different ways to update your Nominatim database. The following section describes how to keep it up-to-date with Pyosmium. For a list of other methods see the output of ./utils/update.php --help.

!!! warning If you have configured a flatnode file for the import, then you need to keep this flatnode file around for updates as well.

Installing the newest version of Pyosmium

It is recommended to install Pyosmium via pip. Make sure to use python3. Run (as the same user who will later run the updates):

pip3 install --user osmium

Nominatim needs a tool called pyosmium-get-updates which comes with Pyosmium. You need to tell Nominatim where to find it. Add the following line to your settings/local.php:

@define('CONST_Pyosmium_Binary', '/home/user/.local/bin/pyosmium-get-changes');

The path above is fine if you used the --user parameter with pip. Replace user with your user name.

Setting up the update process

Next the update needs to be initialised. By default Nominatim is configured to update using the global minutely diffs.

If you want a different update source you will need to add some settings to settings/local.php. For example, to use the daily country extracts diffs for Ireland from Geofabrik add the following:

// base URL of the replication service
@define('CONST_Replication_Url', 'https://download.geofabrik.de/europe/ireland-and-northern-ireland-updates');
// How often upstream publishes diffs
@define('CONST_Replication_Update_Interval', '86400');
// How long to sleep if no update found yet
@define('CONST_Replication_Recheck_Interval', '900');

To set up the update process now run the following command:

./utils/update.php --init-updates

It outputs the date where updates will start. Recheck that this date is what you expect.

The --init-updates command needs to be rerun whenever the replication service is changed.

Updating Nominatim

The following command will keep your database constantly up to date:

./utils/update.php --import-osmosis-all

(Note that even though the old name "import-osmosis-all" has been kept for compatibility reasons, Osmosis is not required to run this - it uses pyosmium behind the scenes.)

If you have imported multiple country extracts and want to keep them up-to-date, have a look at the script in issue #60.