Hive allows loading a table into memory to perform a join within mapper without using reduce.
If the table is small to fit in memory, you can use map-side joins.
This join is performed by importing small table in memory and therefore speeds up query execution.
hive> select /*+ MAPJOIN(product) */ sales.*,product.*
> from sales JOIN product ON (sales.id=product.id);
John 5 5 Shoes
Cena 2 2 Coat
Angle 3 3 Pencil
Raffle 4 4 Shirt
Map joins can be used with bucketed tables also. However, for that, you need to set the property as follow: