Fastest way to filter latitude and longitude from a sql table? - sql

Question

I have a huge table data where sample data is like below. I want to filter few latitude and longitude records from the huge table and I am using In clause to filter list of lat,lon values but when I try to run the query it takes more a min to execute what is the better query to execute it faster? the list of lat,lon is around 120-150
id longitude latitude
--------------------------
190 -0.410123 51.88409
191 -0.413256 51.84567
query:-
SELECT DISTINCT id, longitude, latitude
FROM geo_table
WHERE ROUND(longitude::numeric, 3) IN (-0.418, -0.417, -0.417, -0.416 and so on )
AND ROUND(latitude::numeric, 3) IN (51.884, 51.884, 51.883, 51.883 and so on);

Answer 1

If at least one of the ranges of values in X or Y is tight you can try prefiltering rows. For example, if X (longitude) values are all close together you could try:
SELECT distinct id,longitude,latitude
from (
select *
FROM geo_table
where longitude between -0.418 and -0.416 -- prefilter with index scan
and latitude between 51.883 and 51.884 -- prefilter with index filter
) x
-- now the re-check logic for exact filtering
where ROUND(longitude::numeric,3) in (-0.418, -0.417, -0.417, -0.416, ...)
and ROUND(latitude::numeric,3) in (51.884, 51.884, 51.883, 51.883, ...)
You would need an index with the form:
create index ix1 on geo_table (longitude, latitude);

Answer 2

First, the way you are looking for a list of latitudes and a list of longitudes is likely wrong if you are looking for points locations:
point: lat;long
----------------
Point A: 1;10
Point B: 2;10
Point C: 1;20
Point D: 2;20
--> if you search for latitude in (1;2) and longitude in (10;20), the query will return the 4 points, while if you search for (latitude,longitude) in ((1;10),(2;20)), the query will return only points A and D.
Then, since you are looking for rounded values, you must index the rounded values:
create index latlong_rdn on geo_table (round(longitude,3),round(latitude,3));
and the query should use the exact same expression:
select *
from geo_table
where (round(longitude,3),round(latitude,3)) in
(
(-0.413,51.846),
(-0.410,51.890)
);
But here again rounding is not necessarily the best approach when dealing with locations. You may want to have a look at the PostGIS extension, to save the points as geography, add a spatial index, and to search for points within a distance (st_dwithin()) of the input locations.