All 7 Strings & Bitmaps in Redis questions
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What is the Redis string data type, and what kinds of values can it actually store? What are Redis bitmaps, and how do they let you efficiently work with individual bits within a string? How do you count the number of set bits within a bitmap, and how is this useful for analytics purposes? How do you use the SETRANGE and GETRANGE commands to work with a specific portion of a Redis string without affecting or retrieving the rest of it? How would you use bitmap operations like BITOP to combine multiple daily activity bitmaps and answer questions like how many users were active on both of two specific days? What are practical real world applications where using bitmaps provides a significant memory advantage over alternative approaches like sets?
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How do you atomically increment and decrement a numeric value stored as a Redis string?

Beginner

Answer

You use INCR to atomically increase a numeric string value by one, DECR to atomically decrease it by one, or INCRBY and DECRBY to change it by a specific custom amount, all guaranteed to be safe even if many clients are trying to update the same counter simultaneously.
SET page_views 0
INCR page_views
INCRBY page_views 5
Real-world example A website safely tracks its total page view count using INCR, ensuring the counter remains accurate even when many visitors are loading pages at the exact same moment.

Common follow-ups: What happens if you try to INCR a string that does not hold a valid integer?;Is there an equivalent command for incrementing a floating point number?

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All 7 Strings & Bitmaps in Redis questions