Map Side Join In Hive

One major issue from the common join or sort merged join is too much activity spending on shuffling data. Map join in hive is also called map side join in hive.

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In the last blog i discussed the default join type in hive.

Map side join in hive. Map side joins allows a table to get loaded into memory ensuring a very fast join operation performed. As the name implies the join operation is performed in the map phase itself. Therefore in the map side join the mapper performs the join and it is mandatory that the input to each map is partitioned and sorted according to the keys.

Map side join is a process where joins between two tables are performed in the map phase without the involvement of reduce phase. In this blog i am going to discuss map join also called auto map join or map side join or broadcast join. And the join should be converted to a bucketized map side join or bucketized sort merge join.

However there are many more insights of apache hive map join. In apache hive there is a feature that we use to speed up hive queriesbasically that feature is what we call map join in hive. It lets a table to be loaded into memory so that a join could be performed within a mapper without using a mapreduce step.

In this blog we shall discuss about map side join and its advantages over the normal join operation in hive. Since there is no reducer involved in the map side join it is much faster when compared to regular join. The following configurable parameters can be used to make sure that the query executes in a single map reduce job.

What is map side join in hive. This is an important concept that youll need to learn to implement your big data hadoop certification projects. The map side join has been covered in a separate blog with an example.

If queries frequently depend on small table joins using map joins speed up queries execution. In the last article we discuss map side join in hivebasically while the tables are large and all the tables used in the join are bucketed on the join columns we use a bucket map join in hivein this article we will cover the whole concept of apache hive bucket map join. Also known as replicated join a map side join is a special type of join where a smaller table is loaded in memory and join is performed in map phase of mapreduce job.

Hive supports the following syntax for joining tables. In this blog we will be showing a demo on map side joins in hive. But before knowing about this we should first understand the concept of join and what happens internally when we perform the join in hive.

Configuring map join options in hive map join is a hive feature that is used to speed up hive queries.

Map Side Join Example In Hive Post By Mukund Kumar Mishra