Database / RocksDB Basics Interview Questions
What is Merge in RocksDB?
Merge is a special write operation that lets an application apply an incremental update to a key's value without first reading its current value.
- Common example: incrementing a counter, where you want to add a value rather than overwrite the whole thing
- Requires the application to supply a Merge Operator, custom logic defining how multiple pending merge operations should eventually be combined into a single value
- RocksDB defers actually applying the merge logic until a read happens or compaction processes the relevant data, rather than computing it immediately on every write
This operation avoids the classic read-modify-write pattern's overhead and potential race conditions, letting an application record "add 1" as its own lightweight write instead.
What does Merge let an application avoid?
What must an application supply to use Merge?
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