reintroduce cutoffs when searching for very frequent words

[nominatim.git] / nominatim / api / search / db_search_fields.py

diff --git a/nominatim/api/search/db_search_fields.py b/nominatim/api/search/db_search_fields.py
index 324a7acc2cafe5a553dc60fdb6f5ca1b948568ae..7f775277e6960a7dc37d76a7181b5ad4e4273084 100644 (file)
--- a/nominatim/api/search/db_search_fields.py
+++ b/nominatim/api/search/db_search_fields.py
@@ -7,15 +7,17 @@
 """
 Data structures for more complex fields in abstract search descriptions.
 """
-from typing import List, Tuple, Iterator, cast, Dict
+from typing import List, Tuple, Iterator, Dict, Type
 import dataclasses
 
 import sqlalchemy as sa
 
 from nominatim.typing import SaFromClause, SaColumn, SaExpression
 from nominatim.api.search.query import Token
+import nominatim.api.search.db_search_lookups as lookups
 from nominatim.utils.json_writer import JsonWriter
 
+
 @dataclasses.dataclass
 class WeightedStrings:
     """ A list of strings together with a penalty.
@@ -92,7 +94,7 @@ class RankedTokens:
 
     def with_token(self, t: Token, transition_penalty: float) -> 'RankedTokens':
         """ Create a new RankedTokens list with the given token appended.
-            The tokens penalty as well as the given transision penalty
+            The tokens penalty as well as the given transition penalty
             are added to the overall penalty.
         """
         return RankedTokens(self.penalty + t.penalty + transition_penalty,
@@ -152,18 +154,12 @@ class FieldLookup:
     """
     column: str
     tokens: List[int]
-    lookup_type: str
+    lookup_type: Type[lookups.LookupType]
 
     def sql_condition(self, table: SaFromClause) -> SaColumn:
         """ Create an SQL expression for the given match condition.
         """
-        col = table.c[self.column]
-        if self.lookup_type == 'lookup_all':
-            return col.contains(self.tokens)
-        if self.lookup_type == 'lookup_any':
-            return cast(SaColumn, col.overlaps(self.tokens))
-
-        return sa.func.coalesce(sa.null(), col).contains(self.tokens) # pylint: disable=not-callable
+        return self.lookup_type(table, self.column, self.tokens)
 
 
 class SearchData:
@@ -203,8 +199,7 @@ class SearchData:
             categories: Dict[Tuple[str, str], float] = {}
             min_penalty = 1000.0
             for t in tokens:
-                if t.penalty < min_penalty:
-                    min_penalty = t.penalty
+                min_penalty = min(min_penalty, t.penalty)
                 cat = t.get_category()
                 if t.penalty < categories.get(cat, 1000.0):
                     categories[cat] = t.penalty
@@ -229,22 +224,24 @@ def lookup_by_names(name_tokens: List[int], addr_tokens: List[int]) -> List[Fiel
     """ Create a lookup list where name tokens are looked up via index
         and potential address tokens are used to restrict the search further.
     """
-    lookup = [FieldLookup('name_vector', name_tokens, 'lookup_all')]
+    lookup = [FieldLookup('name_vector', name_tokens, lookups.LookupAll)]
     if addr_tokens:
-        lookup.append(FieldLookup('nameaddress_vector', addr_tokens, 'restrict'))
+        lookup.append(FieldLookup('nameaddress_vector', addr_tokens, lookups.Restrict))
 
     return lookup
 
 
-def lookup_by_any_name(name_tokens: List[int], addr_tokens: List[int],
-                       lookup_type: str) -> List[FieldLookup]:
+def lookup_by_any_name(name_tokens: List[int], addr_restrict_tokens: List[int],
+                       addr_lookup_tokens: List[int]) -> List[FieldLookup]:
     """ Create a lookup list where name tokens are looked up via index
         and only one of the name tokens must be present.
         Potential address tokens are used to restrict the search further.
     """
-    lookup = [FieldLookup('name_vector', name_tokens, 'lookup_any')]
-    if addr_tokens:
-        lookup.append(FieldLookup('nameaddress_vector', addr_tokens, lookup_type))
+    lookup = [FieldLookup('name_vector', name_tokens, lookups.LookupAny)]
+    if addr_restrict_tokens:
+        lookup.append(FieldLookup('nameaddress_vector', addr_restrict_tokens, lookups.Restrict))
+    if addr_lookup_tokens:
+        lookup.append(FieldLookup('nameaddress_vector', addr_lookup_tokens, lookups.LookupAll))
 
     return lookup
 
@@ -253,5 +250,5 @@ def lookup_by_addr(name_tokens: List[int], addr_tokens: List[int]) -> List[Field
     """ Create a lookup list where address tokens are looked up via index
         and the name tokens are only used to restrict the search further.
     """
-    return [FieldLookup('name_vector', name_tokens, 'restrict'),
-            FieldLookup('nameaddress_vector', addr_tokens, 'lookup_all')]
+    return [FieldLookup('name_vector', name_tokens, lookups.Restrict),
+            FieldLookup('nameaddress_vector', addr_tokens, lookups.LookupAll)]