Merge pull request #2746 from bgo-eiu/patch-2

[nominatim.git] / docs / customize / Tokenizers.md

diff --git a/docs/customize/Tokenizers.md b/docs/customize/Tokenizers.md
index f75bc6a5c9da88fad8b92bc046337d2fcebff863..19d867ddd800063494d72ad6ac078025d7ce2347 100644 (file)
--- a/docs/customize/Tokenizers.md
+++ b/docs/customize/Tokenizers.md
@@ -19,7 +19,22 @@ they can be configured.
 
 The legacy tokenizer implements the analysis algorithms of older Nominatim
 versions. It uses a special Postgresql module to normalize names and queries.
-This tokenizer is currently the default.
+This tokenizer is automatically installed and used when upgrading an older
+database. It should not be used for new installations anymore.
+
+### Compiling the PostgreSQL module
+
+The tokeinzer needs a special C module for PostgreSQL which is not compiled
+by default. If you need the legacy tokenizer, compile Nominatim as follows:
+
+```
+mkdir build
+cd build
+cmake -DBUILD_MODULE=on
+make
+```
+
+### Enabling the tokenizer
 
 To enable the tokenizer add the following line to your project configuration:
 
@@ -47,6 +62,7 @@ normalization functions are hard-coded.
 The ICU tokenizer uses the [ICU library](http://site.icu-project.org/) to
 normalize names and queries. It also offers configurable decomposition and
 abbreviation handling.
+This tokenizer is currently the default.
 
 To enable the tokenizer add the following line to your project configuration:
 
@@ -206,15 +222,16 @@ by a sanitizer (see for example the
 The token-analysis section contains the list of configured analyzers. Each
 analyzer must have an `id` parameter that uniquely identifies the analyzer.
 The only exception is the default analyzer that is used when no special
-analyzer was selected.
+analyzer was selected. There is one special id '@housenumber'. If an analyzer
+with that name is present, it is used for normalization of house numbers.
 
 Different analyzer implementations may exist. To select the implementation,
-the `analyzer` parameter must be set. Currently there is only one implementation
-`generic` which is described in the following.
+the `analyzer` parameter must be set. The different implementations are
+described in the following.
 
 ##### Generic token analyzer
 
-The generic analyzer is able to create variants from a list of given
+The generic analyzer `generic` is able to create variants from a list of given
 abbreviation and decomposition replacements and introduce spelling variations.
 
 ###### Variants
@@ -331,6 +348,14 @@ the mode by adding:
 
 to the analyser configuration.
 
+##### Housenumber token analyzer
+
+The analyzer `housenumbers` is purpose-made to analyze house numbers. It
+creates variants with optional spaces between numbers and letters. Thus,
+house numbers of the form '3 a', '3A', '3-A' etc. are all considered equivalent.
+
+The analyzer cannot be customized.
+
 ### Reconfiguration
 
 Changing the configuration after the import is currently not possible, although