# `IndexJoin` and `IndexHashJoin` Operator

__*Adding bullets*__

+ The smaller table involved in a join operation, serving as the `Build side`
+ The larger table involved in a join operation, with an index on the join column, serving as the `Probe side`

![`smart`](IndexJoin01_aa_003_20230913.png)

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The `IndexJoin` or `IndexHashJoin` operators require the driven table to have an index on the join column and high cardinality. This method is typically the most efficient join approach in traditional databases. However, in a distributed database, performance may vary. Let's first examine the underlying principle.