Merge pull request #2597 from lonvia/reorganise-interpolations

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

diff --git a/docs/develop/Tokenizers.md b/docs/develop/Tokenizers.md
index 743e637ce639c1136dc490f2f4f63b06dce44534..28d8fd19733140c6db368238014c8adda0722028 100644 (file)
--- a/docs/develop/Tokenizers.md
+++ b/docs/develop/Tokenizers.md
@@ -6,7 +6,7 @@ tokenizers that use different strategies for normalisation. This page describes
 how tokenizers are expected to work and the public API that needs to be
 implemented when creating a new tokenizer. For information on how to configure
 a specific tokenizer for a database see the
 how tokenizers are expected to work and the public API that needs to be
 implemented when creating a new tokenizer. For information on how to configure
 a specific tokenizer for a database see the

-[tokenizer chapter in the administration guide](../admin/Tokenizers.md).
+[tokenizer chapter in the Customization Guide](../customize/Tokenizers.md).

 
 ## Generic Architecture
 
 
 ## Generic Architecture
 


@@ -50,7 +50,7 @@ tokenizer's internal token lists and creating a list of all token IDs for
 the specific place. This list is later needed in the PL/pgSQL part where the
 indexer needs to add the token IDs to the appropriate search tables. To be
 able to communicate the list between the Python part and the pl/pgSQL trigger,
 the specific place. This list is later needed in the PL/pgSQL part where the
 indexer needs to add the token IDs to the appropriate search tables. To be
 able to communicate the list between the Python part and the pl/pgSQL trigger,

-the placex table contains a special JSONB column `token_info` which is there
+the `placex` table contains a special JSONB column `token_info` which is there

 for the exclusive use of the tokenizer.
 
 The Python part of the tokenizer returns a structured information about the
 for the exclusive use of the tokenizer.
 
 The Python part of the tokenizer returns a structured information about the


@@ -67,12 +67,17 @@ consequently not create any special indexes on it.
 
 ### Querying
 
 
 ### Querying
 

-The tokenizer is responsible for the initial parsing of the query. It needs
-to split the query into appropriate words and terms and match them against
-the saved tokens in the database. It then returns the list of possibly matching
-tokens and the list of possible splits to the query parser. The parser uses
-this information to compute all possible interpretations of the query and
-rank them accordingly.
+At query time, Nominatim builds up multiple _interpretations_ of the search
+query. Each of these interpretations is tried against the database in order
+of the likelihood with which they match to the search query. The first
+interpretation that yields results wins.
+
+The interpretations are encapsulated in the `SearchDescription` class. An
+instance of this class is created by applying a sequence of
+_search tokens_ to an initially empty SearchDescription. It is the
+responsibility of the tokenizer to parse the search query and derive all
+possible sequences of search tokens. To that end the tokenizer needs to parse
+the search query and look up matching words in its own data structures.

 
 ## Tokenizer API
 
 
 ## Tokenizer API
 


@@ -185,22 +190,21 @@ be listed with a semicolon as delimiter. Must be NULL when the place has no
 house numbers.
 
 ```sql
 house numbers.
 
 ```sql

-FUNCTION token_addr_street_match_tokens(info JSONB) RETURNS INTEGER[]
+FUNCTION token_matches_street(info JSONB, street_tokens INTEGER[]) RETURNS BOOLEAN

 ```
 
 ```
 

-Return the match token IDs by which to search a matching street from the
-`addr:street` tag. These IDs will be matched against the IDs supplied by
-`token_get_name_match_tokens`. Must be NULL when the place has no `addr:street`
-tag.
+Check if the given tokens (previously saved from `token_get_name_match_tokens()`)
+match against the `addr:street` tag name. Must return either NULL or FALSE
+when the place has no `addr:street` tag.

 
 ```sql
 
 ```sql

-FUNCTION token_addr_place_match_tokens(info JSONB) RETURNS INTEGER[]
+FUNCTION token_matches_place(info JSONB, place_tokens INTEGER[]) RETURNS BOOLEAN

 ```
 
 ```
 

-Return the match token IDs by which to search a matching place from the
-`addr:place` tag. These IDs will be matched against the IDs supplied by
-`token_get_name_match_tokens`. Must be NULL when the place has no `addr:place`
-tag.
+Check if the given tokens (previously saved from `token_get_name_match_tokens()`)
+match against the `addr:place` tag name. Must return either NULL or FALSE
+when the place has no `addr:place` tag.
+

 
 ```sql
 FUNCTION token_addr_place_search_tokens(info JSONB) RETURNS INTEGER[]
 
 ```sql
 FUNCTION token_addr_place_search_tokens(info JSONB) RETURNS INTEGER[]


@@ -211,26 +215,34 @@ are used for searches by address when no matching place can be found in the
 database. Must be NULL when the place has no `addr:place` tag.
 
 ```sql
 database. Must be NULL when the place has no `addr:place` tag.
 
 ```sql

-CREATE TYPE token_addresstoken AS (
-  key TEXT,
-  match_tokens INT[],
-  search_tokens INT[]
-);
+FUNCTION token_get_address_keys(info JSONB) RETURNS SETOF TEXT
+```
+
+Return the set of keys for which address information is provided. This
+should correspond to the list of (relevant) `addr:*` tags with the `addr:`
+prefix removed or the keys used in the `address` dictionary of the place info.
+
+```sql
+FUNCTION token_get_address_search_tokens(info JSONB, key TEXT) RETURNS INTEGER[]
+```
+
+Return the array of search tokens for the given address part. `key` can be
+expected to be one of those returned with `token_get_address_keys()`. The
+search tokens are added to the address search vector of the place, when no
+corresponding OSM object could be found for the given address part from which
+to copy the name information.

 
 

-FUNCTION token_get_address_tokens(info JSONB) RETURNS SETOF token_addresstoken
+```sql
+FUNCTION token_matches_address(info JSONB, key TEXT, tokens INTEGER[])

 ```
 
 ```
 

-Return the match and search token IDs for explicit `addr:*` tags for the place
-other than `addr:street` and `addr:place`. For each address item there are
-three pieces of information returned:
+Check if the given tokens match against the address part `key`.

 
 

- * _key_ contains the type of address item (city, county, etc.). This is the
-   key handed in with the `address` dictionary.
- * *match_tokens* is the list of token IDs used to find the corresponding
-   place object for the address part. The list is matched against the IDs
-   from `token_get_name_match_tokens`.
- * *search_tokens* is the list of token IDs under which to search the address
-   item. It is used when no corresponding place object was found.
+__Warning:__ the tokens that are handed in are the lists previously saved
+from `token_get_name_search_tokens()`, _not_ from the match token list. This
+is an historical oddity which will be fixed at some point in the future.
+Currently, tokenizers are encouraged to make sure that matching works against
+both the search token list and the match token list.

 
 ```sql
 FUNCTION token_normalized_postcode(postcode TEXT) RETURNS TEXT
 
 ```sql
 FUNCTION token_normalized_postcode(postcode TEXT) RETURNS TEXT


@@ -301,6 +313,14 @@ public function extractTokensFromPhrases(array &$aPhrases) : TokenList
 Parse the given phrases, splitting them into word lists and retrieve the
 matching tokens.
 
 Parse the given phrases, splitting them into word lists and retrieve the
 matching tokens.
 

+The phrase array may take on two forms. In unstructured searches (using `q=`
+parameter) the search query is split at the commas and the elements are
+put into a sorted list. For structured searches the phrase array is an
+associative array where the key designates the type of the term (street, city,
+county etc.) The tokenizer may ignore the phrase type at this stage in parsing.
+Matching phrase type and appropriate search token type will be done later
+when the SearchDescription is built.
+

 For each phrase in the list of phrases, the function must analyse the phrase
 string and then call `setWordSets()` to communicate the result of the analysis.
 A word set is a list of strings, where each string refers to a search token.
 For each phrase in the list of phrases, the function must analyse the phrase
 string and then call `setWordSets()` to communicate the result of the analysis.
 A word set is a list of strings, where each string refers to a search token.