Migrating and handling spatial buffer transformations between Azure SQL and Amazon Redshift
Details
When migrating spatial buffer operations from Azure SQL to Redshift, here are the key conversions and considerations:
-
Syntax Conversion:
From Azure:
geography::Point(Latitude, Longitude, 4326).STBuffer(distance_in_meters)
To Redshift:
ST_Buffer(
ST_SetSRID(ST_Point(Longitude, Latitude), 4326),
distance_in_degrees
)
-
Distance Unit Conversion:
In order to convert to degrees in Redshift use the below conversion formula. This will handle the geographic calculation,
distance_in_degrees = (distance_in_meters / 1000) / (111.32 * COS(RADIANS(Latitude)))
-
Required Modifications:
- Convert distance from meters to degrees
Example:
From Azure:
geography::Point(47.6097, -122.3331, 4326).STBuffer(5000)
To Redshift:
ST_Buffer(
ST_SetSRID(ST_Point(-122.3331, 47.6097), 4326),
5.0 / (111.32 * COS(RADIANS(47.6097)))
)
Test the converted queries thoroughly, as slight variations in buffer calculations might occur due to different geodetic implementations.