Geo-proximity with sorted sets in Redis - Step-by-Step Execution

Concept Flow - Geo-proximity with sorted sets

Add locations with GEOADD

↓

Store locations in sorted set with geo info

↓

Use GEORADIUS or GEOSEARCH to find nearby locations

↓

Sort results by distance

↓

Return locations with distances

Locations are added to a sorted set with geo info, then queried by radius to find and sort nearby places.

Execution Sample

Redis

GEOADD places 13.361389 38.115556 "Palermo"
GEOADD places 15.087269 37.502669 "Catania"
GEORADIUS places 15 37 200 km WITHDIST ASC

Add two places and find all within 200 km of point (15,37), sorted by distance.

Execution Table

Step	Command	Action	Result	Notes
1	GEOADD places 13.361389 38.115556 "Palermo"	Add Palermo location	Added 1	Palermo stored in 'places' sorted set
2	GEOADD places 15.087269 37.502669 "Catania"	Add Catania location	Added 1	Catania stored in 'places' sorted set
3	GEORADIUS places 15 37 200 km WITHDIST ASC	Find locations within 200 km of (15,37)	[["Catania", 56.4413], ["Palermo", 190.4424]]	Results sorted by distance ascending
4	End	No more commands	Query complete	Execution stops after query

💡 All commands executed; GEORADIUS returns sorted nearby locations within radius.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
places	empty	[Palermo]	[Palermo, Catania]	[Palermo, Catania]	[Palermo, Catania]
query_result	none	none	none	[[Catania, 56.4413], [Palermo, 190.4424]]	[[Catania, 56.4413], [Palermo, 190.4424]]

Key Moments - 2 Insights

Why does GEORADIUS return Catania before Palermo even though Palermo was added first?

GEORADIUS sorts results by distance when ASC is specified, so Catania is closer to (15,37) than Palermo, shown in execution_table row 3.

What does the WITHDIST option do in the GEORADIUS command?

WITHDIST makes GEORADIUS return the distance of each location from the center point, as seen in the result distances in execution_table row 3.

Visual Quiz - 3 Questions

Look at the execution_table row 3, what is the distance from (15,37) to Palermo?

A 15 km

B 56.4413 km

C 190.4424 km

D 37 km

💡 Hint

Check the distances listed in the GEORADIUS result in execution_table row 3.

At which step is the second location added to the sorted set?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at the commands in execution_table rows 1 and 2.

If the radius in GEORADIUS was changed to 50 km, what would happen to the query_result?

A Both Palermo and Catania would be returned

B No locations would be returned

C Only Palermo would be returned

D Only Catania would be returned

💡 Hint

Refer to the distances in execution_table row 3 and compare with 50 km radius.

Concept Snapshot

GEOADD key longitude latitude member - adds geo location to sorted set
GEORADIUS key longitude latitude radius m|km WITHDIST ASC|DESC - finds nearby locations sorted by distance
WITHDIST returns distance with each location
Results sorted by distance if ASC or DESC specified
Use for geo proximity queries in Redis

Full Transcript

This visual execution shows how Redis stores geo locations in a sorted set using GEOADD. Two locations, Palermo and Catania, are added with their longitude and latitude. Then GEORADIUS queries locations within 200 km of point (15,37), returning Catania and Palermo sorted by distance ascending. The WITHDIST option includes the distance in the results. The execution table tracks each command and result, and the variable tracker shows how the 'places' set and query results change. Key moments clarify why sorting happens by distance and what WITHDIST does. The quiz tests understanding of distances, command steps, and radius effects. This helps beginners see step-by-step how geo proximity queries work with Redis sorted sets.