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avoid index-use on rank parameters for reverse lookups

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This commit is contained in:
Sarah Hoffmann
2023-07-08 21:47:07 +02:00
parent f4cdcb995c
commit d743cf308e
2 changed files with 19 additions and 10 deletions
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25
nominatim/api/reverse.py
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@@ -28,6 +28,13 @@ RowFunc = Callable[[Optional[SaRow], Type[nres.ReverseResult]], Optional[nres.Re
WKT_PARAM: SaBind = sa.bindparam('wkt', type_=Geometry) WKT_PARAM: SaBind = sa.bindparam('wkt', type_=Geometry)
MAX_RANK_PARAM: SaBind = sa.bindparam('max_rank') MAX_RANK_PARAM: SaBind = sa.bindparam('max_rank')
def no_index(expr: SaColumn) -> SaColumn:
""" Wrap the given expression, so that the query planner will
refrain from using the expression for index lookup.
"""
return sa.func.coalesce(sa.null(), expr) # pylint: disable=not-callable
def _select_from_placex(t: SaFromClause, use_wkt: bool = True) -> SaSelect: def _select_from_placex(t: SaFromClause, use_wkt: bool = True) -> SaSelect:
""" Create a select statement with the columns relevant for reverse """ Create a select statement with the columns relevant for reverse
results. results.
@@ -172,12 +179,17 @@ class ReverseGeocoder:
""" """
t = self.conn.t.placex t = self.conn.t.placex
# PostgreSQL must not get the distance as a parameter because
# there is a danger it won't be able to proberly estimate index use
# when used with prepared statements
dist_param = sa.text(f"{distance}")
sql = _select_from_placex(t)\ sql = _select_from_placex(t)\
.where(t.c.geometry.ST_DWithin(WKT_PARAM, distance))\ .where(t.c.geometry.ST_DWithin(WKT_PARAM, dist_param))\
.where(t.c.indexed_status == 0)\ .where(t.c.indexed_status == 0)\
.where(t.c.linked_place_id == None)\ .where(t.c.linked_place_id == None)\
.where(sa.or_(sa.not_(t.c.geometry.is_area()), .where(sa.or_(sa.not_(t.c.geometry.is_area()),
t.c.centroid.ST_Distance(WKT_PARAM) < distance))\ t.c.centroid.ST_Distance(WKT_PARAM) < dist_param))\
.order_by('distance')\ .order_by('distance')\
.limit(1) .limit(1)
@@ -186,17 +198,16 @@ class ReverseGeocoder:
restrict: List[SaColumn] = [] restrict: List[SaColumn] = []
if self.layer_enabled(DataLayer.ADDRESS): if self.layer_enabled(DataLayer.ADDRESS):
restrict.append(sa.and_(t.c.rank_address >= 26, restrict.append(no_index(t.c.rank_address).between(26, min(29, self.max_rank)))
t.c.rank_address <= min(29, self.max_rank)))
if self.max_rank == 30: if self.max_rank == 30:
restrict.append(_is_address_point(t)) restrict.append(_is_address_point(t))
if self.layer_enabled(DataLayer.POI) and self.max_rank == 30: if self.layer_enabled(DataLayer.POI) and self.max_rank == 30:
restrict.append(sa.and_(t.c.rank_search == 30, restrict.append(sa.and_(no_index(t.c.rank_search) == 30,
t.c.class_.not_in(('place', 'building')), t.c.class_.not_in(('place', 'building')),
sa.not_(t.c.geometry.is_line_like()))) sa.not_(t.c.geometry.is_line_like())))
if self.has_feature_layers(): if self.has_feature_layers():
restrict.append(sa.and_(t.c.rank_search.between(26, MAX_RANK_PARAM), restrict.append(sa.and_(no_index(t.c.rank_search).between(26, MAX_RANK_PARAM),
t.c.rank_address == 0, no_index(t.c.rank_address) == 0,
self._filter_by_layer(t))) self._filter_by_layer(t)))
if not restrict: if not restrict:

4
nominatim/db/sqlalchemy_types.py
View File

@@ -48,9 +48,7 @@ class Geometry(types.UserDefinedType): # type: ignore[type-arg]
def bind_expression(self, bindvalue: SaBind) -> SaColumn: def bind_expression(self, bindvalue: SaBind) -> SaColumn:
return sa.func.ST_GeomFromText(bindvalue, return sa.func.ST_GeomFromText(bindvalue, sa.text('4326'), type_=self)
sa.bindparam('geometry_srid', value=4326, literal_execute=True),
type_=self)
class comparator_factory(types.UserDefinedType.Comparator): # type: ignore[type-arg] class comparator_factory(types.UserDefinedType.Comparator): # type: ignore[type-arg]