X-Git-Url: https://git.openstreetmap.org./nominatim.git/blobdiff_plain/f1fe70656f88c558a6f4bf6a09adde4ef59487fb..771aee8cd80f9dc5303331053e9b08a901a620e0:/docs/develop/Import.md diff --git a/docs/develop/Import.md b/docs/develop/Import.md index e733c6fd..0f98dafc 100644 --- a/docs/develop/Import.md +++ b/docs/develop/Import.md @@ -1,8 +1,8 @@ # OSM Data Import -OSM data is initially imported using osm2pgsql. Nominatim uses its own data -output style 'gazetteer', which differs from the output style created for -map rendering. +OSM data is initially imported using [osm2pgsql](https://osm2pgsql.org). +Nominatim uses its own data output style 'gazetteer', which differs from the +output style created for map rendering. ## Database Layout @@ -24,147 +24,4 @@ with multiple tags that may constitute a principal tag. Take for example a motorway bridge. In OSM, this would be a way which is tagged with `highway=motorway` and `bridge=yes`. This way would appear in the `place` table once with `class` of `highway` and once with a `class` of `bridge`. Thus the -*uique key* for `place` is (`osm_type`, `osm_id`, `class`). - -## Configuring the Import - -How tags are interpreted and assigned to the different `place` columns can be -configured via the import style configuration file (`CONST_Import_style`). This -is a JSON file which contains a list of rules which are matched against every -tag of every object and then assign the tag its specific role. - -### Configuration Rules - -A single rule looks like this: - -```json -{ - "keys" : ["key1", "key2", ...], - "values" : { - "value1" : "prop", - "value2" : "prop1,prop2" - } -} -``` - -A rule first defines a list of keys to apply the rule to. This is always a list -of strings. The string may have four forms. An empty string matches against -any key. A string that ends in an asterisk `*` is a prefix match and accordingly -matches against any key that starts with the given string (minus the `*`). A -suffix match can be defined similarly with a string that starts with a `*`. Any -other string constitutes an exact match. - -The second part of the rules defines a list of values and the properties that -apply to a successful match. Value strings may be either empty, which again -means that thy match against any value, or describe an exact match. Prefix -or suffix matching of values is not possible. - -For a rule to match, it has to find a valid combination of keys and values. The -resulting property is that of the matched values. - -The rules in a configuration file are processed sequentially and the first -match for each tag wins. - -A rule where key and value are the empty string is special. This defines the -fallback when none of the rules matches. The fallback is always used as a last -resort when nothing else matches, no matter where the rule appears in the file. -Defining multiple fallback rules is not allowed. What happens in this case, -is undefined. - -### Tag Properties - -One or more of the following properties may be given for each tag: - -* `main` - - A principal tag. A new row will be added for the object with key and value - as `class` and `type`. - -* `with_name` - - When the tag is a principal tag (`main` property set): only really add a new - row, if there is any name tag found (a reference tag is not sufficient, see - below). - -* `with_name_key` - - When the tag is a principal tag (`main` property set): only really add a new - row, if there is also a name tag that matches the key of the principal tag. - For example, if the main tag is `bridge=yes`, then it will only be added as - an extra row, if there is a tag `bridge:name[:XXX]` for the same object. - If this property is set, all other names that are not domain-specific are - ignored. - -* `fallback` - - When the tag is a principal tag (`main` property set): only really add a new - row, when no other principal tags for this object have been found. Only one - fallback tag can win for an object. - -* `operator` - - When the tag is a principal tag (`main` property set): also include the - `operator` tag in the list of names. This is a special construct for an - out-dated tagging practise in OSM. Fuel stations and chain restaurants - in particular used to have the name of the chain tagged as `operator`. - These days the chain can be more commonly found in the `brand` tag but - there is still enough old data around to warrant this special case. - -* `name` - - Add tag to the list of names. - -* `ref` - - Add tag to the list of names as a reference. At the moment this only means - that the object is not considered to be named for `with_name`. - -* `address` - - At tag to the list of address tags. If the tag starts with `addr:` or - `is_in:`, then this prefix is cut off before adding it to the list. - -* `postcode` - - At the value as a postcode to the address tags. If multiple tags are - candidate for postcodes, one wins out and the others are dropped. - -* `country` - - At the value as a country code to the address tags. The value must be a - two letter country code, otherwise it is ignored. If there are multiple - tags that match, then one wins out and the others are dropped. - -* `house` - - If no principle tags can be found for the object, still add the object with - `class`=`place` and `type`=`house`. Use this for address nodes that have no - other function. - -* `interpolation` - - Add this object as an address interpolation (appears as `class`=`place` and - `type`=`houses` in the database). - -* `extra` - - Add tag to the list of extra tags. - -* `skip` - - Skip the tag completely. Useful when a custom default fallback is defined - or to define exceptions to rules. - -A rule can define as many of these properties for one match as it likes. For -example, if the property is `"main,extra"` then the tag will open a new row -but also have the tag appear in the list of extra tags. - -There are a number of pre-defined styles in the `settings/` directory. It is -advisable to start from one of these styles when defining your own. - -### Changing the Style of Existing Databases - -There is normally no issue changing the style of a database that is already -imported and now kept up-to-date with change files. Just be aware that any -change in the style applies to updates only. If you want to change the data -that is already in the database, then a reimport is necessary. +*unique key* for `place` is (`osm_type`, `osm_id`, `class`).