Geo-proximity with sorted sets in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a location with longitude and latitude to a sorted set.

Redis

GEOADD locations 13.361389 38.115556 [1]

Drag options to blanks, or click blank then click option'

ASicily

BSicilyKey

CSicilyLocation

DSicilySet

Attempts:

3 left

💡 Hint

Common Mistakes

Using the key name instead of the member name.

Confusing longitude and latitude order.

The GEOADD command adds a location with longitude and latitude to the sorted set named locations. The first arguments after the key are longitude and latitude, followed by the member name, here Sicily.

2fill in blank

medium

Complete the code to find locations within 100 km radius from given coordinates.

Redis

GEORADIUS locations 15 37 [1] km

Drag options to blanks, or click blank then click option'

A150

B100

C50

D200

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong radius value.

Confusing meters and kilometers.

The GEORADIUS command finds members within a radius. Here, the radius is 100 kilometers.

3fill in blank

hard

Fix the error in the command to get the distance between two locations.

Redis

GEODIST locations Sicily [1] km

Drag options to blanks, or click blank then click option'

APalermo

BPalermoLocation

CPalermoKey

DPalermoSet

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect member names.

Adding extra suffixes to member names.

The GEODIST command calculates the distance between two members. The member name must match exactly, here Palermo.

4fill in blank

hard

Fill both blanks to get locations within 50 km and sort results by distance.

Redis

GEORADIUS locations 15 37 [1] km [2]

Drag options to blanks, or click blank then click option'

A50

BASC

CDESC

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong radius value.

Using DESC instead of ASC for sorting.

The radius is 50 km, and ASC sorts results from nearest to farthest.

5fill in blank

hard

Fill all three blanks to get locations within 100 km, sorted ascending, and include distances in output.

Redis

GEORADIUS locations 15 37 [1] km [2] WITHDIST [3]

Drag options to blanks, or click blank then click option'

AASC

BDESC

CCOUNT 5

D100

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up ASC and DESC.

Forgetting to include WITHDIST for distances.

The radius is 100 km, sorting ascending with ASC, and limiting results to 5 with COUNT 5. The WITHDIST option includes distances in the output.

Practice

1. What does the Redis command GEOADD do in the context of geo-proximity with sorted sets?

easy

A. Returns the distance between two members

B. Finds all members within a radius from a point

C. Removes a location from the sorted set

D. Adds geographic locations (longitude, latitude) to a sorted set

Solution

1. Step 1: Understand the purpose of GEOADD

   The GEOADD command stores geographic coordinates (longitude and latitude) associated with a member in a sorted set.

2. Step 2: Differentiate GEOADD from other geo commands

   Commands like GEORADIUS find nearby members, while GEOADD adds new locations.

3. Final Answer:

   Adds geographic locations (longitude, latitude) to a sorted set -> Option D

4. Quick Check:

   GEOADD = Add locations [OK]

Hint: GEOADD always adds locations with coordinates [OK]

Common Mistakes:

• Confusing GEOADD with GEORADIUS
• Thinking GEOADD removes locations
• Assuming GEOADD returns distances

2. Which of the following is the correct syntax to find members within 5 kilometers of longitude 13.361389 and latitude 38.115556 using Redis GEO commands?

easy

A. GEOADD locations 13.361389 38.115556 5 km

B. GEODIST locations 13.361389 38.115556 5 km

C. GEORADIUS locations 13.361389 38.115556 5 km

D. GEORADIUSBYMEMBER locations 13.361389 38.115556 5 km

Solution

1. Step 1: Identify the command to find nearby members

   GEORADIUS is used to find members within a radius from given longitude and latitude.

2. Step 2: Check syntax correctness

   GEORADIUS locations 13.361389 38.115556 5 km correctly specifies key, longitude, latitude, radius, and unit.

3. Final Answer:

   GEORADIUS locations 13.361389 38.115556 5 km -> Option C

4. Quick Check:

   GEORADIUS + lon lat + radius + unit = correct syntax [OK]

Hint: Use GEORADIUS with lon lat radius unit for proximity search [OK]

Common Mistakes:

• Using GEOADD instead of GEORADIUS for searching
• Mixing GEORADIUSBYMEMBER syntax with coordinates
• Using GEODIST which calculates distance, not radius search

3. Given the following Redis commands executed in order:

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

What will be the output?

medium

A. [["Palermo", "56.4413"], ["Catania", "190.4424"]]

B. [["Catania", "56.4413"], ["Palermo", "190.4424"]]

C. ["Palermo", "Catania"]

D. Syntax error

Solution

1. Step 1: Add two cities with their coordinates

   Palermo and Catania are added with their longitude and latitude to the 'cities' key.

2. Step 2: Use GEORADIUS to find cities within 200 km of (15, 37) sorted by distance ascending

   Catania is closer (~56.44 km), Palermo is farther (~190.44 km), so output lists Catania first with distances.

3. Final Answer:

   [["Catania", "56.4413"], ["Palermo", "190.4424"]] -> Option B

4. Quick Check:

   GEORADIUS WITHDIST ASC sorts by nearest first [OK]

Hint: WITHDIST returns distances; ASC sorts nearest first [OK]

Common Mistakes:

• Confusing order of results when using ASC
• Ignoring WITHDIST option for distances
• Swapping longitude and latitude values

4. You run the command GEORADIUS cities 15 37 100 km WITHDIST but get no results, even though you know cities exist nearby. What is the most likely cause?

medium

A. The key 'cities' does not exist or is empty

B. The longitude and latitude are swapped

C. The radius is too small to include any city

D. WITHDIST option is not supported

Solution

1. Step 1: Check if the key exists and has data

   If the 'cities' key does not exist or is empty, GEORADIUS returns no results regardless of radius.

2. Step 2: Consider other causes

   Radius 100 km is reasonable, WITHDIST is supported, and longitude/latitude order is correct, so these are less likely.

3. Final Answer:

   The key 'cities' does not exist or is empty -> Option A

4. Quick Check:

   Empty key = no results [OK]

Hint: Check if key exists before searching [OK]

Common Mistakes:

• Assuming WITHDIST causes errors
• Swapping lat/lon but still expecting results
• Using too small radius without verifying data

5. You want to find all locations within 10 miles of 'Denver' stored in a Redis sorted set 'places'. Which command correctly finds these locations using the member name 'Denver' as center and returns results sorted from nearest to farthest?

hard

A. GEORADIUSBYMEMBER places Denver 10 mi WITHDIST ASC

B. GEORADIUS places Denver 10 mi WITHDIST ASC

C. GEORADIUSBYMEMBER places Denver 10 mi WITHDIST DESC

D. GEODIST places Denver 10 mi WITHDIST ASC

Solution

1. Step 1: Use GEORADIUSBYMEMBER to search by member name

   GEORADIUSBYMEMBER finds locations near a member's coordinates, here 'Denver'.

2. Step 2: Specify radius and unit, and sort ascending by distance

   10 miles radius with WITHDIST ASC returns nearby locations sorted nearest first.

3. Final Answer:

   GEORADIUSBYMEMBER places Denver 10 mi WITHDIST ASC -> Option A

4. Quick Check:

   GEORADIUSBYMEMBER + WITHDIST ASC = nearest first [OK]

Hint: Use GEORADIUSBYMEMBER for member-centered radius search [OK]

Common Mistakes:

• Using GEORADIUS with member name instead of coordinates
• Sorting DESC instead of ASC for nearest first
• Using GEODIST which returns distance between two members only