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Data & Analytics · Advanced

Broadcast Join

A join strategy that sends a copy of a small table to every executor so the large table is joined without being shuffled.

Definition

Spark broadcasts tables below spark.sql.autoBroadcastJoinThreshold (10 MB by default) or when hinted with broadcast(). It is very efficient for star-schema joins of large facts to small dimensions.

Example

large_df.join(F.broadcast(dim_df), 'product_id')

Exam tip

Large fact joined to a small dimension = broadcast join.

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