Redis ZINTER in Python (Detailed Guide w/ Code Examples)

Use Case(s)

The ZINTER command in Redis is used to perform an intersection of multiple sorted sets, and it stores the result in a new sorted set. It's commonly used in scenarios where you want to find common elements across different groups with their scores combined or compared.

Code Examples

Example 1: Basic Intersection of Two Sorted Sets

In this example, we use ZINTER to find the intersection of two sorted sets and store the results in a new set.

import redis # Connect to Redis client = redis.Redis(host='localhost', port=6379, db=0) # Adding some sample sorted sets client.zadd('scores_set1', {'Alice': 50, 'Bob': 100}) client.zadd('scores_set2', {'Alice': 70, 'Charlie': 80}) # Intersect two sets and store the result in a new set client.zinterstore('intersection_result', ['scores_set1', 'scores_set2']) # Fetching and displaying the result print(client.zrange('intersection_result', 0, -1, withscores=True))

This code snippet will output:

[(b'Alice', 120.0)]

indicating that Alice is present in both sets and her scores from both sets are added together.

Example 2: Intersection with Custom Aggregate Function

You can specify how the scores should be aggregated during the intersection. Here, we use the maximum score instead of summing them.

# Intersect two sets using max as aggregate function client.zinterstore('max_intersection_result', ['scores_set1', 'scores_set2'], aggregate='MAX') # Fetching and displaying the result print(client.zrange('max_intersection_result', 0, -1, withscores=True))

This outputs:

[(b'Alice', 70.0)]

showing the highest score Alice received among the two sets.

Best Practices

  • Use Appropriate Aggregation: Choose the aggregation method (SUM, MIN, MAX) wisely based on your application needs when using zinterstore.
  • Memory Management: When working with large data sets, be conscious of memory usage since storing intersections could potentially consume significant memory resources.

Common Mistakes

  • Ignoring Score Aggregation: Not specifying an aggregation method when different behavior is expected can lead to incorrect data outcomes.
  • Data Overwrite: Be careful with the destination key in zinterstore as it can overwrite existing data without warning.


Q: Can ZINTER intersect more than two sorted sets?

A: Yes, ZINTER can take multiple sorted set keys as input and will intersect all of them according to specified weights and aggregate functions.

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