Partitioning

Partition a Key Space

Partitioning maps each key to exactly one partition.

highlighted = computed this step

Partition a key space

A partitioning scheme maps each key to exactly one partition. This book keeps the model tiny: pinned integer keys, range or hash routing, and exact movement after rebalance. Note: real skew, hot partitions, and rebalancing cost are outside this exact model.

routing function\text{routing function}

Key space split into partitions

The compiled scheme has 4 partitions and routes 4 pinned keys. Note: the table is the recomputed routing result grouped by partition.

partitions=4,keys=4\text{partitions}=4,\quad \text{keys}=4

Range and hash sharding are exact routing functions on tiny pinned key sets; real sharding adds consistent hashing, skew, hot partitions, and rebalancing cost, which are empirical and operational concerns beyond this model - no product claims.

Partitioned key space - range:10,20,30partitioncountkeysP014P1114P2124P3134

Summary

Partitioning is an exact function from key to partition in this model. Note: operational placement and performance claims are deferred.

one key maps to one partition\text{one key maps to one partition}