Optimizing Geospatial Queries with PostGIS

# Optimizing Geospatial Queries with PostGIS

PostGIS is a powerful spatial database extension for PostgreSQL. Learn how to optimize location-based queries for production applications.

## Getting Started with PostGIS

First, enable PostGIS in your database:

```sql
CREATE EXTENSION postgis;
```

## Spatial Indexes

The key to fast geospatial queries is proper indexing:

```sql
CREATE INDEX idx_locations_geom
ON locations USING GIST (geom);
```

## Radius Searches

Find all locations within a radius:

```sql
SELECT * FROM locations
WHERE ST_DWithin(
geom,
ST_SetSRID(ST_MakePoint(-73.935242, 40.730610), 4326),
5000 -- 5km radius
);
```

## Performance Tips

1. **Use Geography for long distances**
2. **Always create GIST indexes**
3. **Use ST_DWithin instead of ST_Distance**
4. **Simplify geometries when appropriate**

## Real-World Example

Building a delivery radius checker:

```python
from django.contrib.gis.db.models.functions import Distance
from django.contrib.gis.geos import Point

location = Point(-73.935242, 40.730610, srid=4326)
restaurants = Restaurant.objects.annotate(
distance=Distance('location', location)
).filter(
location__dwithin=(location, 5000)
).order_by('distance')
```

## Conclusion

PostGIS is essential for location-based applications. With proper indexing and query optimization, you can handle millions of spatial records efficiently.