Nominatim/docs/admin/Import.md

Importing the Database

The following instructions explain how to create a Nominatim database from an OSM planet file. It is assumed that you have already successfully installed the Nominatim software itself and the nominatim tool can be found in your PATH. If this is not the case, return to the installation page.

Creating the project directory

Before you start the import, you should create a project directory for your new database installation. This directory receives all data that is related to a single Nominatim setup: configuration, extra data, etc. Create a project directory apart from the Nominatim software and change into the directory:

mkdir ~/nominatim-planet
cd ~/nominatim-planet

In the following, we refer to the project directory as $PROJECT_DIR. To be able to copy&paste instructions, you can export the appropriate variable:

export PROJECT_DIR=~/nominatim-planet

The Nominatim tool assumes per default that the current working directory is the project directory but you may explicitly state a different directory using the --project-dir parameter. The following instructions assume that you run all commands from the project directory.

!!! tip "Migration Tip"

Nominatim used to be run directly from the build directory until version 3.6.
Essentially, the build directory functioned as the project directory
for the database installation. This setup still works and can be useful for
development purposes. It is not recommended anymore for production setups.
Create a project directory that is separate from the Nominatim software.

Configuration setup in .env

The Nominatim server can be customized via a .env in the project directory. This is a file in dotenv format which looks the same as variable settings in a standard shell environment. You can also set the same configuration via environment variables. All settings have a NOMINATIM_ prefix to avoid conflicts with other environment variables.

There are lots of configuration settings you can tweak. Have a look at settings/env.default 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 .env:

NOMINATIM_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 75GB 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. Put it into your project directory:

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

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

!!! tip If you forgot to download the wikipedia rankings, you can also add importances after the import. Download the files, then run nominatim refresh --wiki-data --importance. Updating importances for a planet can take a couple of hours.

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 into the project directory:

cd $PROJECT_DIR
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 900GB 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 OSM 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 in the next section. 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, you can run the import with the --no-updates parameter. This will drop the dynamic part of the database as soon as it is not required anymore.

You can also drop the dynamic part later using the following command:

nominatim freeze

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 NOMINATIM_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 2020 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 NVME disks. 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	4h	215 GB	20 GB
street	22h	440 GB	185 GB
address	36h	545 GB	260 GB
full	54h	640 GB	330 GB
extratags	54h	650 GB	340 GB

You can also customize the styles further. A description of the style format can be found in 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. Then issue the following command from the build directory to start the import:

nominatim import --osm-file <data file> 2>&1 | tee setup.log

Notes on full planet imports

Even on a perfectly configured machine the import of a full planet takes around 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 you are importing. The size needs to be given in MB. 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.

Testing the installation

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

nominatim admin --check-database

Now you can try out your installation by running:

nominatim serve

This runs a small test server normally used for development. You can use it to verify that your installation is working. Go to http://localhost:8088/status.php and you should see the message OK. You can also run a search query, e.g. http://localhost:8088/search.php?q=Berlin.

To run Nominatim via webservers like Apache or nginx, please read the Deployment chapter.

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:

nominatim refresh --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 import these key phrases like this:

nominatim special-phrases --import-from-wiki

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 2020 data and unpack it into your project directory:

   cd $PROJECT_DIR wget https://nominatim.org/data/tiger2020-nominatim-preprocessed.tar.gz tar xf tiger2020-nominatim-preprocessed.tar.gz

2. Import the data into your Nominatim database:

   nominatim add-data --tiger-data tiger

3. Enable use of the Tiger data in your .env by adding:

   echo NOMINATIM_USE_US_TIGER_DATA=yes >> .env

4. Apply the new settings:

   nominatim refresh --functions

See the developer's guide for more information on how the data got preprocessed.